Derivative Financial Instruments and Off-balance sheet Financial Instruments (Details 7) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Derivative Financial Instruments and Off-balance sheet Financial Instruments
Commitments to invest in limited partnership interests	$ 2,551	$ 2,429
Commitments to extend mortgage loans	0	49
Private placement commitments	89	98
Municipal bond forward commitments	36	0
Other loan commitments	46	$ 46
Municipal Bond Forward Commitments, Fair Value	$ 1