Income Taxes Deferred Tax Assets and Liabilities (Details) - USD ($)	Dec. 31, 2015	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Deferred Tax Assets, Operating Loss Carryforwards	$ 0
Deferred Tax Assets, Tax Credit Carryforwards, Partnership, Net of Uncertain Tax Position Liabilities	3,400,000,000
Deferred Tax Assets, Tax Credit Carryforwards, Alternative Minimum Tax	308,000,000
Deferred tax assets:
Mortgage and mortgage-related assets	16,956,000,000	$ 16,250,000,000
Allowance for loan losses and basis in acquired property, net	11,760,000,000	17,435,000,000
Debt and derivative instruments	3,512,000,000	4,254,000,000
Partnership credits	3,402,000,000	2,918,000,000
Partnership and other equity investments	745,000,000	934,000,000
Other, net	1,543,000,000	1,699,000,000
Total deferred tax assets	37,918,000,000	43,490,000,000
Deferred tax liabilities:
Unrealized gains on AFS securities, net	731,000,000	1,134,000,000
Total deferred tax liabilities	731,000,000	1,134,000,000
Valuation allowance	0	(150,000,000)
Net deferred tax assets	$ 37,187,000,000	$ 42,206,000,000