Fresh Start Accounting - Enterprise Value To The Estimated Fair Value Of The Successor Common Stock (Details) - USD ($)
$ / shares in Units, $ in Millions
Sep. 30, 2018
Dec. 16, 2017
Dec. 15, 2017
Fresh-Start Adjustment [Line Items]      
Enterprise value     $ 5,721
Plus:      
Cash and cash equivalents   $ 366 366
Less:      
Minimum cash required for operations     (120)
Fair value of Term Loan Credit Agreement     (2,896)
Fair value of capitalized leases     (20)
Fair value of pension and other post-retirement obligations, net of tax     (856)
Change in net deferred tax liabilities from reorganization     (510)
Fair value of Successor Emergence Date Warrants     (17)
Fair value of Successor common stock   1,668 $ 1,668
Shares issued at December 15, 2017 (in shares) 110,218,653   110,000,000
Per share value (usd per share)     $ 15.16
Debt, fair value, percent of par     99.00%
Post-retirement Benefits      
Less:      
Rate of return on plan assets     5.90%
Discount rate     3.77%
U.S. | Pension Plan      
Less:      
Rate of return on plan assets     7.75%
Discount rate 4.22%   3.70%
U.S. | Post-retirement Benefits      
Less:      
Discount rate 4.26%    
Non-US | Pension Plan      
Less:      
Rate of return on plan assets     3.80%
Discount rate 1.92%   1.52%
As Previously Reported      
Fresh-Start Adjustment [Line Items]      
Enterprise value     $ 5,721
Plus:      
Cash and cash equivalents   340 340
Less:      
Minimum cash required for operations     (120)
Fair value of Term Loan Credit Agreement     (2,896)
Fair value of capitalized leases     (20)
Fair value of pension and other post-retirement obligations, net of tax     (856)
Change in net deferred tax liabilities from reorganization     (510)
Fair value of Successor Emergence Date Warrants     (17)
Fair value of Successor common stock   1,642 $ 1,642
Shares issued at December 15, 2017 (in shares) 110,218,653   110,000,000
Per share value (usd per share)     $ 14.93
Adjustments      
Fresh-Start Adjustment [Line Items]      
Enterprise value     $ 0
Plus:      
Cash and cash equivalents   26 26
Less:      
Minimum cash required for operations     0
Fair value of Term Loan Credit Agreement     0
Fair value of capitalized leases     0
Fair value of pension and other post-retirement obligations, net of tax     0
Change in net deferred tax liabilities from reorganization     0
Fair value of Successor Emergence Date Warrants     0
Fair value of Successor common stock   $ 26 $ 26
Shares issued at December 15, 2017 (in shares)     0
Per share value (usd per share)     $ 0.23