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Annual report pursuant to Section 13 and 15(d)

PENSIONS AND OTHER POSTRETIREMENT BENEFITS (Narrative) (Details)

v3.8.0.1
PENSIONS AND OTHER POSTRETIREMENT BENEFITS (Narrative) (Details) - USD ($)
 12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Defined Benefit Plan Disclosure [Line Items] Ìý Ìý
401(k) contribution match $ 0.50 Ìý
Minimum participants percentage 15.00% Ìý
Defined Benefit Plan, Accumulated Benefit Obligation $ 963,000,000 $ 922,000,000
Reserve for investment commitments $ 52,700,000 Ìý
Structured Finance [Member] Ìý Ìý
Defined Benefit Plan Disclosure [Line Items] Ìý Ìý
Redemption request notice period, days 90 days Ìý
Real Estate [Member] Ìý Ìý
Defined Benefit Plan Disclosure [Line Items] Ìý Ìý
Redemption request notice period, days 45 days Ìý
Withdrawal request notice period, days 65 days Ìý
Pension Benefits [Member] Ìý Ìý
Defined Benefit Plan Disclosure [Line Items] Ìý Ìý
Decrease in Projected Benefit Obligation due to Market Conditions $ 46,100,000 Ìý
Reduction in net periodic benefit expense 8,200,000 Ìý
Increase in Projected Benefit Obligation due to new mortality tables $ 6,100,000 $ 13,100,000
Percentage Increase in Projected Benefit Obligation due to new mortality tables 0.60% 1.40%
Other Benefits [Member] Ìý Ìý
Defined Benefit Plan Disclosure [Line Items] Ìý Ìý
Defined Benefit Plan, Plan Assets, Contributions by Plan Participant $ 4,600,000 $ 6,000,000
Decrease in Projected Benefit Obligation due to Market Conditions 12,600,000 Ìý
Reduction in net periodic benefit expense 1,800,000 Ìý
Increase in Projected Benefit Obligation due to new mortality tables $ 1,900,000 $ 4,900,000
Percentage Increase in Projected Benefit Obligation due to new mortality tables 0.70% 1.80%
Prior To Age65 [Member] | United States [Member] Ìý Ìý
Defined Benefit Plan Disclosure [Line Items] Ìý Ìý
Annual limit on medical coverage for each participant $ 7,000 Ìý
Prior To Age65 [Member] | Minimum [Member] | Northshore [Member] Ìý Ìý
Defined Benefit Plan Disclosure [Line Items] Ìý Ìý
Annual limit on medical coverage for each participant 4,020 Ìý
Prior To Age65 [Member] | Maximum [Member] | Northshore [Member] Ìý Ìý
Defined Benefit Plan Disclosure [Line Items] Ìý Ìý
Annual limit on medical coverage for each participant $ 4,500 Ìý