Goodwill, Other Intangibles, and Property and Equipment - Other Intangible Assets (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Finite Lived Intangible Assets Net [Line Items]
Cost	$ 4,240	$ 3,935
Accumulated amortization	2,754	2,367
Net carrying value	1,486	1,568
Other Assets [Member]
Finite Lived Intangible Assets Net [Line Items]
Cost	1,566	1,579
Accumulated amortization	998	870
Net carrying value	568	709
Customer Relationships [Member] | Other Assets [Member]
Finite Lived Intangible Assets Net [Line Items]
Cost	1,264	1,266
Accumulated amortization	867	779
Net carrying value	397	487
Other Intangibles [Member] | Other Assets [Member]
Finite Lived Intangible Assets Net [Line Items]
Cost	302	313
Accumulated amortization	131	91
Net carrying value	171	222
Value Of Business Acquired [Member] | Deferred Policy Acquisition Costs [Member]
Finite Lived Intangible Assets Net [Line Items]
Cost	232	165
Accumulated amortization	48	30
Net carrying value	184	135
Internal-use software [Member] | Property And Equipment [Member]
Finite Lived Intangible Assets Net [Line Items]
Cost	2,442	2,191
Accumulated amortization	1,708	1,467
Net carrying value	$ 734	$ 724