Consolidated Statements of Shareholders' Equity - USD ($) $ in Millions		Total	Common Stock [Member]	Preferred Stock [Member]	Additional Paid-in Capital [Member]	AOCI Attributable to Parent [Member]	Retained Earnings [Member]
Preferred Stock, Shares Outstanding				0
Balance at beginning of period (shares) at Dec. 31, 2014	[1]		5,050,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock issued (shares)			0	0
Balance at end of period (shares) at Dec. 31, 2015	[1]		5,050,000
Balance at beginning of period at Dec. 31, 2014			$ 0	$ 0	$ 5,799	$ (433)	$ 2,026
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock issued			0	0
Stock-based compensation expense					35
Capital contributions from related party					649
Differences between tax payments due under consolidated return and separate return basis					1
Preferred Stock					0
Other comprehensive income (loss), net of tax						(671)
Net income		$ 646					646
Balance at end of period at Dec. 31, 2015			$ 0	$ 0	6,484	(1,104)	2,672
Preferred Stock, Shares Outstanding				0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock issued (shares)			0	0
Balance at end of period (shares) at Dec. 31, 2016	[1]		5,050,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock issued			$ 0	$ 0
Stock-based compensation expense					21
Capital contributions from related party					0
Differences between tax payments due under consolidated return and separate return basis					0
Preferred Stock					0
Other comprehensive income (loss), net of tax						(134)
Net income		754					754
Balance at end of period at Dec. 31, 2016		8,693	$ 0	$ 0	6,505	(1,238)	3,426
Preferred Stock, Shares Outstanding				0
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock issued (shares)			0	1,000,000,000
Balance at end of period (shares) at Dec. 31, 2017			5,050,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock issued			$ 0	$ 0
Stock-based compensation expense					35
Capital contributions from related party					0
Differences between tax payments due under consolidated return and separate return basis					0
Preferred Stock					985
Other comprehensive income (loss), net of tax						470
Dividends paid							(550)
Net income		661					661
Balance at end of period at Dec. 31, 2017		$ 10,294	$ 0	$ 0	$ 7,525	$ (768)	$ 3,537
Preferred Stock, Shares Outstanding				1,000,000,000

[1] All shares have been retroactively adjusted to reflect the stock split executed on September 1, 2017. Refer to Note 12 for further information.