Derivative Financial Instruments and Off-balance sheet Financial Instruments (Details 7) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Derivative Financial Instruments and Off-balance sheet Financial Instruments
Commitments to invest in limited partnership interests	$ 2,979	$ 2,551
Private placement commitments	69	89
Municipal bond forward commitments	0	36
Other loan commitments	$ 83	$ 46