Investments (Consolidated Variable Interest Entities) (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015
Assets:
Accrued investment income relating to variable interest entities	$ 591	$ 505
Liabilities
Long-term debt, at estimated fair value, relating to variable interest entities	804	836
Other liabilities relating to variable interest entities	10,147	7,682
Consolidated securitization entities
Assets:
Mortgage loans (commercial mortgage loans)	136	172
Accrued investment income relating to variable interest entities	1	1
Total assets	137	173
Liabilities
Long-term debt, at estimated fair value, relating to variable interest entities	23	48
Other liabilities relating to variable interest entities	1	1
Total liabilities	$ 24	$ 49