Condensed Consolidated Statements of Changes in Shareholder's Equity - USD ($) $ in Millions	Total	Common Stock	Additional Paid-In Capital	Accumulated Other Comprehensive Income (Loss)	Retained Earnings (Deficit)	Previously Reported	Previously Reported Common Stock	Previously Reported Additional Paid-In Capital	Previously Reported Accumulated Other Comprehensive Income (Loss)	Previously Reported Retained Earnings (Deficit)
Increase (Decrease) in Stockholders' Equity
Cumulative Effect of New Accounting Principle in Period of Adoption | Accounting Standards Update 2014-09	$ 72	$ 0	$ 0	$ 0	$ 72
Cumulative Effect of New Accounting Principle in Period of Adoption | Accounting Standards Update 2016-01	0	0	0	(12)	12
Beginning Balance at Dec. 31, 2017						$ 3,581	$ 3	$ 2,730	$ 818	$ 30
Balance as adjusted at Dec. 31, 2017	3,653	3	2,730	806	114
Comprehensive income (loss):
Net income (loss)	347	0	0	0	347
Other comprehensive income (loss), after tax	(605)	0	0	(605)	0
Comprehensive income (loss)	(258)
Dividends paid and distributions of capital	(126)	0	0	0	(126)
Employee related benefits	(2)	0	(2)	0	0
Ending Balance at Sep. 30, 2018	3,267	3	2,728	201	335
Beginning Balance at Jun. 30, 2018	3,166	3	2,729	260	174
Comprehensive income (loss):
Net income (loss)	161	0	0	0	161
Other comprehensive income (loss), after tax	(59)	0	0	(59)	0
Comprehensive income (loss)	102
Employee related benefits	(1)	0	(1)	0	0
Ending Balance at Sep. 30, 2018	3,267	3	2,728	201	335
Increase (Decrease) in Stockholders' Equity
Cumulative Effect of New Accounting Principle in Period of Adoption | Accounting Standards Update 2018-02	0	0	0	137	(137)
Beginning Balance at Dec. 31, 2018	3,322	3	2,728	108	483
Comprehensive income (loss):
Net income (loss)	304	0	0	0	304
Other comprehensive income (loss), after tax	1,121	0	0	1,121	0
Comprehensive income (loss)	1,425
Dividends paid and distributions of capital	(396)	0	0	0	(396)
Employee related benefits	0	0	0	0	0
Ending Balance at Sep. 30, 2019	4,351	3	2,728	1,366	254
Increase (Decrease) in Stockholders' Equity
Cumulative Effect of New Accounting Principle in Period of Adoption | Accounting Standards Update 2018-02	0	0	0	0	0
Beginning Balance at Jun. 30, 2019	4,015	3	2,728	1,140	144
Comprehensive income (loss):
Net income (loss)	110	0	0	0	110
Other comprehensive income (loss), after tax	226	0	0	226	0
Comprehensive income (loss)	336
Dividends paid and distributions of capital	0	0	0	0	0
Ending Balance at Sep. 30, 2019	$ 4,351	$ 3	$ 2,728	$ 1,366	$ 254