Consolidated Statements of Comprehensive Income (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Statement Of Comprehensive Income [Abstract]
Shareholders' Net Income	$ 1,623	$ 1,260	$ 1,279
Net unrealized appreciation (deprecation) on securities:
Net unrealized appreciation (depreciation), fixed maturities	144	210	151
Net unrealized appreciation (depreciation), equity securities	3	(2)	(1)
Net unrealized appreciation (depreciation) on securities	147	208	150
Net unrealized appreciation (depreciation), derivatives	(5)	1	6
Net translation of foreign currencies	66	(22)	33
Postretirement benefits liability adjustment	(92)	(360)	(189)
Shareholders' other comprehensive income (loss)	116	(173)	0
Shareholders' comprehensive income	1,739	1,087	1,279
Comprehensive income attributable to noncontrolling interest:
Net income attributable to redeemable noncontrolling interest	1	0	0
Net income attributable to other noncontrolling interest	0	1	4
Other comprehensive income attributable to redeemable noncontrolling interest	2	0	0
Other comprehensive income attributable to other noncontrolling interest	0	0	2
Total comprehensive income	$ 1,742	$ 1,088	$ 1,285