Consolidated Statements of Shareholders' Comprehensive Income - USD ($) $ in Millions	3 Months Ended											12 Months Ended
	Dec. 31, 2015	[1]	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
Statement Of Comprehensive Income [Abstract]
Shareholders' Net Income	$ 426		$ 547		$ 588		$ 533	$ 467	$ 534	$ 573	$ 528	$ 2,094	$ 2,102	$ 1,476
Shareholders' other comprehensive income (loss):
Net unrealized appreciation (depreciation) on securities												(202)	143	(410)
Net unrealized appreciation (depreciation), derivatives												15	11	9
Net translation of foreign currencies												(212)	(144)	13
Postretirement benefits liability adjustment												85	(426)	539
Shareholders' other comprehensive income (loss)												(314)	(416)	151
Shareholders' comprehensive income (loss)												$ 1,780	$ 1,686	$ 1,627

[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.