Mortgage Loans Credit Quality Indicators - MF (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Financing Receivable, Recorded Investment [Line Items]
Total recorded investment	$ 3,095,816	$ 3,035,712
Multifamily [Member]
Financing Receivable, Recorded Investment [Line Items]
Total recorded investment	231,881	200,174
Multifamily [Member] | Non-classified [Member]
Financing Receivable, Recorded Investment [Line Items]
Total recorded investment	228,749	197,334
Multifamily [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Total recorded investment	3,129	2,833
Multifamily [Member] | Doubtful [Member]
Financing Receivable, Recorded Investment [Line Items]
Total recorded investment	3	7
Multifamily [Member] | Total classified [Member]
Financing Receivable, Recorded Investment [Line Items]
Total recorded investment	$ 3,132	$ 2,840