ACQUISITIONS - AK Steel Consideration (Details) $ / shares in Units, $ in Millions |
Mar. 13, 2020
USD ($)
$ / shares
shares
|
Sep. 30, 2021
shares
|
Jun. 30, 2021
shares
|
Mar. 31, 2021
shares
|
Dec. 31, 2020
shares
|
Sep. 30, 2020
shares
|
Jun. 30, 2020
shares
|
Mar. 31, 2020
shares
|
Dec. 31, 2019
shares
|
---|---|---|---|---|---|---|---|---|---|
Business Acquisition [Line Items] | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý |
Common shares, outstanding (in shares) | shares | Ìý | 500,055,941 | Ìý | Ìý | 477,517,372 | Ìý | Ìý | Ìý | Ìý |
AK Steel | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý |
Business Acquisition [Line Items] | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý |
Fair value of debt included in consideration | $ 914 | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý |
Fair value of Cliffs common shares issued for AK Steel outstanding common stock | 618 | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý |
Other | 3 | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý |
Consideration transferred | $ 1,535 | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý |
Common shares, outstanding (in shares) | shares | 317,000,000 | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý |
Exchange ratio | 0.400 | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý |
Shares of Cliffs common shares issued to AK Steel stockholders (in shares) | shares | 127,000,000 | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý |
Price per share of Cliffs common shares (in dollars per share) | $ / shares | $ 4.87 | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý |
ABL Facility | AK Steel | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý |
Business Acquisition [Line Items] | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý |
Fair value of debt included in consideration | $ 590 | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý |
7.500% Senior Secured Notes due July 2023 | AK Steel | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý |
Business Acquisition [Line Items] | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý |
Fair value of debt included in consideration | 324 | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý |
Common Stock | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý |
Business Acquisition [Line Items] | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý |
Common shares, outstanding (in shares) | shares | Ìý | 500,000,000 | 500,000,000 | 499,000,000 | 478,000,000 | 399,000,000 | 399,000,000 | 399,000,000 | 271,000,000 |
Common Stock | AK Steel | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý |
Business Acquisition [Line Items] | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý |
Fair value of Cliffs common shares issued for AK Steel outstanding common stock | $ 618 | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý |
Common Stock | AK Steel | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý |
Business Acquisition [Line Items] | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý |
Exchange ratio | 0.400 | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý | Ìý |
X | ||||||||||
- Definition Business Acquisition, Shares Exchange Ratio No definition available.
|
X | ||||||||||
- Definition Value of equity interests (such as common shares, preferred shares, or partnership interest) issued or issuable to acquire the entity. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
|
X | ||||||||||
- Definition Number of shares of equity interests issued or issuable to acquire entity. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
|
X | ||||||||||
- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. No definition available.
|
X | ||||||||||
- Definition Price of a single share of a number of saleable stocks paid or offered to be paid in a business combination. No definition available.
|
X | ||||||||||
- Definition Amount of consideration transferred, consisting of acquisition-date fair value of assets transferred by the acquirer, liabilities incurred by the acquirer, and equity interest issued by the acquirer. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
|
X | ||||||||||
- Definition Amount of liabilities incurred by the acquirer as part of consideration transferred in a business combination. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
|
X | ||||||||||
- Definition Amount of tangible or intangible assets, including a business or subsidiary of the acquirer transferred by the entity to the former owners of the acquiree. Excludes cash. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
|
X | ||||||||||
- Definition Number of shares of common stock outstanding. Common stock represent the ownership interest in a corporation. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
|
X | ||||||||||
- Details
|
X | ||||||||||
- Details
|
X | ||||||||||
- Details
|
X | ||||||||||
- Details
|
X | ||||||||||
- Details
|