Schedule II. Condensed Financial Information of Registrant (Parent Company) (Schedule of Condensed Financial Information of Registrant, Statements of Cash Flows) (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	[1]	Mar. 31, 2015	Dec. 31, 2016		Dec. 31, 2015		Dec. 31, 2014
Cash Flows from Operating Activities
Net income (loss)	$ 241	$ 343	$ 209	$ 66	[1]	$ (70)	[2]	$ 178	$ 138		$ 233	$ 859	[1]	$ 479	[1],[2]	$ 691
Adjustments to reconcile net income (loss) to net cash flows provided (used) by operating activities:
Net realized investment (gains) losses												(50)		67		(57)
Other, net												29		(2)		54
Total adjustments												557		908		749
Net cash flows provided (used) by operating activities												1,416		1,387		1,440
Cash Flows from Investing Activities
Change in short term investments												258		34		(388)
Other, net												2		21		16
Net cash flows provided (used) by investing activities												(846)		(372)		(918)
Cash Flows from Financing Activities
Dividends paid to common stockholders												(813)		(811)		(541)
Proceeds from the issuance of debt												498		0		546
Repayment of debt												(358)		0		(549)
Other, net												0		4		25
Net cash flows provided (used) by financing activities												(673)		(807)		(519)
Net change in cash												(116)		197		(5)
Cash, beginning of year				387							190	387		190		195
Cash, end of year	271					387						271		387		190
Parent Company [Member]
Cash Flows from Operating Activities
Net income (loss)												859		479		691
Adjustments to reconcile net income (loss) to net cash flows provided (used) by operating activities:
Equity in net income (loss) of subsidiaries												(978)		(594)		(838)
Dividends received from subsidiaries												765		900		650
Net realized investment (gains) losses												7		(5)		(4)
Other, net												21		4		14
Total adjustments												(185)		305		(178)
Net cash flows provided (used) by operating activities												674		784		513
Cash Flows from Investing Activities
Change in short term investments												(9)		21		6
Capital contributions to subsidiaries												0		0		(10)
Other, net												4		7		5
Net cash flows provided (used) by investing activities												(5)		28		1
Cash Flows from Financing Activities
Dividends paid to common stockholders												(813)		(811)		(541)
Proceeds from the issuance of debt												498		0		546
Repayment of debt												(358)		0		(549)
Stock options exercised												0		1		5
Other, net												1		1		25
Net cash flows provided (used) by financing activities												(672)		(809)		(514)
Net change in cash												(3)		3		0
Cash, beginning of year				$ 4							$ 1	4		1		1
Cash, end of year	$ 1					$ 4						$ 1		$ 4		$ 1

[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.