Consolidated Statements of Shareholders' Equity - USD ($) $ in Millions	Total	Common Stock [Member]	Additional Paid-in Capital [Member]	AOCI Attributable to Parent [Member]	Retained Earnings [Member]
Balance at beginning of period (shares) at Dec. 31, 2013		502
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock issued (shares)		3
Balance at end of period (shares) at Dec. 31, 2014		505
Balance at beginning of period at Dec. 31, 2013		$ 0	$ 4,785	$ 11	$ 1,489
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock issued		0
Stock-based compensation expense			18
Capital contributions from related party			996
Differences between tax payments due under consolidated return and separate return basis			0
Other comprehensive loss, net of tax				(444)
Net income	$ 537				537
Balance at end of period at Dec. 31, 2014		$ 0	5,799	(433)	2,026
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock issued (shares)		0
Balance at end of period (shares) at Dec. 31, 2015		505
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock issued		$ 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
Other comprehensive loss, net of tax				(671)
Net income	646				646
Balance at end of period at Dec. 31, 2015	8,052	$ 0	6,484	(1,104)	2,672
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock issued (shares)		0
Balance at end of period (shares) at Dec. 31, 2016		505
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock issued		$ 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
Other comprehensive loss, net of tax				(134)
Net income	754
Balance at end of period at Dec. 31, 2016	$ 8,693	$ 0	$ 6,505	$ (1,238)	$ 3,426