Schedule II - Condensed Financial Information, Statements of Cash Flows (Details) - USD ($) $ in Millions	3 Months Ended											12 Months Ended
	Dec. 31, 2015		Sep. 30, 2015	[1]	Jun. 30, 2015	[2]	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Cash Flows from Operating Activities
Shareholders' net income	$ 426	[1]	$ 547		$ 588		$ 533	$ 467	$ 534	$ 573	$ 528	$ 2,094	$ 2,102	$ 1,476
Adjustments to reconcile shareholders' net income to net cash provided by (used in) operating activities:
Loss on extinguishment of debt												100	0	0
Other liabilities												423	202	(483)
Other, net												(8)	(83)	(82)
Net cash provided by / (used in) operating activities												2,717	1,994	719
Cash Flows from Investing Activities
Short term investments purchased												(1,183)	(2,115)	(1,930)
Other, net												0	(24)	(42)
Net cash provided by/ (used in) investing activities												(1,599)	(1,755)	15
Cash Flows from Financing Activities
Net change in short-term debt												(21)	(112)	(101)
Net proceeds on issuance of long-term debt												894	0	0
Repayment of long-term debt												(938)	0	(15)
Issuance of common stock												154	110	150
Repurchase of common stock												(671)	(1,612)	(1,003)
Net cash provided by / (used in) financing activities												(530)	(1,582)	(930)
Net increase (decrease) in cash and cash equivalents												548	(1,375)	(183)
Cash and cash equivalents, January 1							1,420				2,795	1,420	2,795	2,978
Cash and cash equivalents, December 31	1,968							1,420				1,968	1,420	2,795
Parent Company [Member]
Cash Flows from Operating Activities
Shareholders' net income												2,094	2,102	1,476
Adjustments to reconcile shareholders' net income to net cash provided by (used in) operating activities:
Equity in income from subsidiaries												(2,454)	(2,358)	(1,702)
Dividends received from subsidiaries												880	1,648	506
Loss on extinguishment of debt												100	0	0
Other liabilities												112	(73)	(245)
Other, net												33	173	63
Net cash provided by / (used in) operating activities												765	1,492	98
Cash Flows from Investing Activities
Short term investments purchased												(54)	0	0
Other, net												(14)	11	0
Net cash provided by/ (used in) investing activities												(68)	11	0
Cash Flows from Financing Activities
Net change in amounts due to / from affiliates												(161)	61	751
Net change in short-term debt												0	0	(100)
Net proceeds on issuance of long-term debt												894	0	0
Repayment of long-term debt												(938)	0	0
Issuance of common stock												154	110	150
Common dividends paid												(10)	(11)	(11)
Repurchase of common stock												(671)	(1,612)	(1,003)
Net cash provided by / (used in) financing activities												(732)	(1,452)	(213)
Net increase (decrease) in cash and cash equivalents												(35)	51	(115)
Cash and cash equivalents, January 1							$ 51				$ 0	51	0	115
Cash and cash equivalents, December 31	$ 16							$ 51				$ 16	$ 51	$ 0

[1] Shareholders’ net income includes after-tax charges of $29 million in the third quarter of 2015 and $28 million in the fourth quarter of 2015 for advisory, legal and other transactions costs directly related to the Company’s proposed merger with Anthem. See Note 3 to the Consolidated Financial Statements for additional details.

[2] Shareholders’ net income includes an after-tax charge of $65 million for the early extinguishment of debt in the second quarter of 2015. See Note 15 to the Consolidated Financial Statements for additional details.