Mortgage Loans Credit Quality Indicators - MF (Details) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Financing Receivable, Recorded Investment [Line Items]
Total recorded investment	$ 3,035,712	$ 3,047,794
Multifamily [Member]
Financing Receivable, Recorded Investment [Line Items]
Total recorded investment	200,174	189,233
Multifamily [Member] | Pass [Member]
Financing Receivable, Recorded Investment [Line Items]
Total recorded investment	194,132	182,079
Multifamily [Member] | Special Mention [Member]
Financing Receivable, Recorded Investment [Line Items]
Total recorded investment	3,202	3,070
Multifamily [Member] | Substandard [Member]
Financing Receivable, Recorded Investment [Line Items]
Total recorded investment	2,833	3,842
Multifamily [Member] | Doubtful [Member]
Financing Receivable, Recorded Investment [Line Items]
Total recorded investment	$ 7	$ 242