Schedule II - Condensed Financial Information, Statements of Income (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended											12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013		Sep. 30, 2013	Jun. 30, 2013		Mar. 31, 2013		Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Operating expenses:
Total operating expenses												$ 8,369	$ 7,830	$ 7,414
Income before Income Taxes	732	818	901	853	536		799	767		74		3,304	2,176	2,477
Income tax expense (benefit)												1,210	698	853
Shareholders' Net Income	467	534	573	528	361	[1]	553	505	[2]	57	[3]	2,102	1,476	1,623
Shareholders' other comprehensive income (loss):
Net unrealized appreciation (depreciation) on securities												143	(410)	147
Net unrealized appreciation (depreciation), derivatives												11	9	(5)
Net translation of foreign currencies												(144)	13	66
Postretirement benefits liability adjustment												(426)	539	(92)
Shareholders' other comprehensive income (loss)												(416)	151	116
Shareholders' comprehensive income (loss)												1,686	1,627	1,739
Parent Company [Member]
Operating expenses:
Interest Expense												258	264	262
Intercompany Interest Expense												5	2	0
Other operating expenses												82	69	190
Total operating expenses												345	335	452
Income before Income Taxes												(345)	(335)	(452)
Income tax expense (benefit)												(89)	(109)	(143)
(Loss) of parent company												(256)	(226)	(309)
Equity in income from subsidiaries												2,358	1,702	1,932
Shareholders' Net Income												2,102	1,476	1,623
Shareholders' other comprehensive income (loss):
Net unrealized appreciation (depreciation) on securities												143	(410)	147
Net unrealized appreciation (depreciation), derivatives												11	9	(5)
Net translation of foreign currencies												(144)	13	66
Postretirement benefits liability adjustment												(426)	539	(92)
Shareholders' other comprehensive income (loss)												(416)	151	116
Shareholders' comprehensive income (loss)												$ 1,686	$ 1,627	$ 1,739

[1] The fourth quarter of 2013 includes an after-tax charge of $40 million for an organizational efficiency plan.

[2] The second quarter of 2013 includes an after-tax charge of $24 million for the Pharmacy Benefits Manager (“PBM”) partnering agreement with Catamaran.

[3] The first quarter of 2013 includes an after-tax gain of $25 million for the GMIB business, an after-tax charge of $507 million for the transaction with Berkshire to effectively exit the Run-off Reinsurance business, and an after-tax charge of $51 million related to the disability claims regulatory matter in the Group Disability and Life segment.