Income Taxes Schedule of Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Deferred Tax Assets and Liabilities [Line Items]
Deferred Tax Assets, Tax Credit Carryforwards	$ 1,987	$ 1,941
Deferred Tax Assets, Tax Loss Carryforward	936	950
Deferred Tax Assets, Tax Deferred Expense, Reserves and Accruals, Accrued Liabilities	546	311
Deferred Tax Assets, State and local taxes	162	194
Deferred Tax Assets, Tax Deferred Expense, Reserves and Accruals, Unearned Premiums Reserve	141	141
Deferred Tax Assets, Hedging Transactions	123	99
Deferred Tax Assets, Other	208	212
Deferred Tax Assets, Gross	4,103	3,848
Deferred Tax Assets, Valuation Allowance	(646)	(582)
Deferred Tax Assets, Net of Valuation Allowance	3,457	3,266
Deferred Tax Liabilities, Leasing Arrangements	1,789	1,273
Deferred tax liabilities, deferred expense, deferred acquisition cost	424	403
Deferred Tax Liabilities, Financing Arrangements	161	162
Deferred Tax Liabilities, Other	107	69
Deferred Tax Liabilities, Gross	2,481	1,907
Deferred Tax Assets, Net, Inclusive of Deferred Tax Liabilities	976	1,359
Other Assets	6,854	6,321
Accounts Payable and Accrued Liabilities	1,737	1,545
Deferred Tax Asset [Member]
Deferred Tax Assets and Liabilities [Line Items]
Other Assets	994	1,369
Deferred Tax Liability [Member]
Deferred Tax Assets and Liabilities [Line Items]
Accounts Payable and Accrued Liabilities	$ 18	$ 10