Finite Lived Intangible Assets (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Finite Lived Intangible Assets Net [Line Items]
Cost	$ 3,516	$ 2,310
Accumulated amortization	1,739	1,394
Net carrying value	1,777	916
Other Assets [Member]
Finite Lived Intangible Assets Net [Line Items]
Cost	1,606	710
Accumulated amortization	546	340
Net carrying value	1,060	370
Customer Relationships [Member] | Other Assets [Member]
Finite Lived Intangible Assets Net [Line Items]
Cost	1,278	583
Accumulated amortization	466	313
Net carrying value	812	270
Weighted Average Amortization Period (Years)	10	13
Other Intangibles [Member] | Other Assets [Member]
Finite Lived Intangible Assets Net [Line Items]
Cost	328	127
Accumulated amortization	80	27
Net carrying value	248	100
Weighted Average Amortization Period (Years)	11	12
Value Of Business Acquired [Member] | Deferred Policy Acquisition Costs [Member]
Finite Lived Intangible Assets Net [Line Items]
Cost	172
Accumulated amortization	2
Net carrying value	170
Weighted Average Amortization Period (Years)	26
Internal-use software [Member] | Property And Equipment [Member]
Finite Lived Intangible Assets Net [Line Items]
Cost	1,738	1,600
Accumulated amortization	1,191	1,054
Net carrying value	$ 547	$ 546
Weighted Average Amortization Period (Years)	5	5