Income Taxes (Details 2) - USD ($) $ in Millions	Dec. 31, 2017	Dec. 31, 2016
Deferred tax assets:
Reserves not yet deducted for tax purposes	$ 2,724	$ 3,889
Employee compensation and benefits	403	595
Deferred Tax Assets, Other	409	592
Gross deferred tax assets	3,536	5,076
Valuation allowance	(46)	(54)
Deferred tax assets after valuation allowance	3,490	5,022
Deferred tax liabilities:
Intangibles and fixed assets	1,057	1,691
Deferred revenue	306	441
Deferred interest	183	305
Asset Securitization	0	0
Investment in joint ventures	137	209
Foreign deferred tax liabilities	259	121
Gross deferred tax liabilities	1,942	2,767
Net deferred tax assets	$ 1,548	$ 2,255