Income Taxes Deferred Tax Assets and Liabilities (Details) - USD ($)	Dec. 31, 2020	Jan. 01, 2020	Dec. 31, 2019
Deferred tax assets:
Mortgage and mortgage-related assets	$ 8,241,000,000		$ 9,290,000,000
Allowance for loan losses and basis in acquired property, net	1,798,000,000		1,240,000,000
Debt and derivative instruments	526,000,000		627,000,000
Partnership and other equity investments	129,000,000		152,000,000
Deferred Tax Assets, Investments	2,561,000,000		788,000,000
Total deferred tax assets	13,255,000,000		12,097,000,000
Deferred tax liabilities:
Unrealized gains on AFS securities, net	20,000,000		26,000,000
Deferred Tax Liabilities, Other	288,000,000		161,000,000
Total deferred tax liabilities	308,000,000		187,000,000
Net deferred tax assets	$ 12,947,000,000	$ 12,213,000,000	$ 11,910,000,000