Stockholders' Equity Stockholders' Equity (Narrative) (Details) - USD ($) $ in Millions		8 Months Ended	12 Months Ended
	Aug. 30, 2017	Aug. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2017	Dec. 31, 2014
Predecessor [Member]
Class of Stock [Line Items]
Treasury Stock, Shares	87,041,000	0	87,041,000	87,041,000		87,041,000
Excess of Cost of Treasury Stock over Par Value		$ 0	$ 0	$ 0
Tax benefit (expense) recorded in Stockholders' Equity			33	(138)
Tax benefits			21	37
Successor [Member]
Class of Stock [Line Items]
Treasury Stock, Shares		0			0
Retained Earnings [Member] | Predecessor [Member]
Class of Stock [Line Items]
Excess of Cost of Treasury Stock over Par Value	$ 5,657	$ 5,657	758	1,890
Additional Paid-in Capital [Member] | Predecessor [Member]
Class of Stock [Line Items]
Excess of Cost of Treasury Stock over Par Value	$ 1,044	$ 1,044	$ 154	$ 451