Schedule II. Condensed Financial Information of Registrant (Parent Company) (Schedule of Condensed Financial Information of Registrant, Statements of Operations and Comprehensive Income) (Details) - USD ($) $ in Millions	3 Months Ended											12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016		Dec. 31, 2015		Sep. 30, 2015	Jun. 30, 2015		Mar. 31, 2015	Dec. 31, 2016		Dec. 31, 2015		Dec. 31, 2014
Revenues
Net realized investment gains (losses)												$ 50		$ (67)		$ 57
Total revenues	$ 2,390	$ 2,433	$ 2,348	$ 2,195		$ 2,269		$ 2,153	$ 2,327		$ 2,352	9,366		9,101		9,692
Claims, Benefits and Expenses
Interest												159		155		183
Income tax expense (benefit)												(278)		(70)		(319)
Net income (loss)	$ 241	$ 343	$ 209	$ 66	[1]	$ (70)	[2]	$ 178	$ 138	[1]	$ 233	859	[1]	479	[1],[2]	691
Total comprehensive income (loss)												1,001		(236)		649
Parent Company [Member]
Revenues
Net investment income												3		1		1
Net realized investment gains (losses)												(7)		5		4
Total revenues												(4)		6		5
Claims, Benefits and Expenses
Administrative and general												1		1		5
Interest												155		154		182
Total expenses												156		155		187
Income (loss) from operations before income taxes and equity in net income of subsidiaries												(160)		(149)		(182)
Income tax expense (benefit)												41		34		35
Income (loss) before equity in net income (loss) of subsidiaries												(119)		(115)		(147)
Equity in net income of subsidiaries												978		594		838
Net income (loss)												859		479		691
Equity in other comprehensive income of subsidiaries												142		(715)		(42)
Total comprehensive income (loss)												$ 1,001		$ (236)		$ 649

[1] Net income (loss) in the first quarter of 2016 and the second quarter of 2015 included a charge related to the application of retroactive reinsurance accounting to adverse reserve development ceded under the 2010 A&EP Loss Portfolio Transfer in our Corporate & Other Non-Core segment.

[2] Net income (loss) in the fourth quarter of 2015 included a charge related to recognition of a premium deficiency in our long term care business.