Condensed Consolidated Statements of Shareholders' Equity - USD ($) $ in Millions	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	Retained Earnings [Member]	AOCI Attributable to Parent [Member]	Parent [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative Effect of New Accounting Principle in Period of Adoption | Accounting Standards Update 2014-09 [Member]		$ 0	$ 0	$ 17	$ 0	$ 17
Balance at period start at Dec. 31, 2017		2	3,850	171	(494)	3,529
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cash dividend, preferred stock		0	0	(7)	0	(7)
Tax Cuts and Jobs Act, Reclassification from AOCI to Retained Earnings, Tax Effect	$ (5)	0	0	5	(5)	0
Proceeds, Issuance of Shares, Share-based Payment Arrangement, Including Option Exercised		0	21	0	0	21
Net income (loss)	(276)	0	0	(276)	0	(276)
Other Comprehensive Income (Loss), Net of Tax	75	0	0	0	75	75
Comprehensive Income (Loss), Net	(201)	0	0	(276)	75	(201)
Balance at period end at Sep. 30, 2018		2	3,871	(90)	(424)	3,359
Balance at period start at Jun. 30, 2018		2	3,865	144	(512)	3,499
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cash dividend, preferred stock		0	0	(2)	0	(2)
Tax Cuts and Jobs Act, Reclassification from AOCI to Retained Earnings, Tax Effect		0	0	5	(5)	0
Proceeds, Issuance of Shares, Share-based Payment Arrangement, Including Option Exercised		0	(6)	0	0	(6)
Net income (loss)	(237)	0	0	(237)	0	(237)
Other Comprehensive Income (Loss), Net of Tax	93	0	0	0	93	93
Comprehensive Income (Loss), Net	(144)	0	0	(237)	93	(144)
Balance at period end at Sep. 30, 2018		2	3,871	(90)	(424)	3,359
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cumulative Effect of New Accounting Principle in Period of Adoption | Accounting Standards Update 2016-02		0	0	(8)	0	(8)
Balance at period start at Dec. 31, 2018	3,222	2	3,878	(233)	(425)	3,222
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cash dividend, preferred stock		0	0	(7)	0	(7)
Proceeds, Issuance of Shares, Share-based Payment Arrangement, Including Option Exercised		0	(8)	0	0	(8)
Net income (loss)	(1,353)	0	0	(1,353)	0	(1,353)
Other Comprehensive Income (Loss), Net of Tax	6	0	0	0	6	6
Comprehensive Income (Loss), Net	(1,347)	0	0	(1,353)	6	(1,347)
Balance at period end at Sep. 30, 2019	1,868	2	3,886	(1,601)	(419)	1,868
Balance at period start at Jun. 30, 2019		2	3,886	(1,583)	(404)	1,901
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Cash dividend, preferred stock		0	0	(2)	0	(2)
Net income (loss)	(16)	0	0	(16)	0	(16)
Other Comprehensive Income (Loss), Net of Tax	(15)	0	0	0	(15)	(15)
Comprehensive Income (Loss), Net	(31)	0	0	(16)	(15)	(31)
Balance at period end at Sep. 30, 2019	$ 1,868	$ 2	$ 3,886	$ (1,601)	$ (419)	$ 1,868