Summary of Significant Accounting Policies (Life Settlement Contracts) (Details) $ in Millions	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Life Settlement Contracts, Fair Value Method, Number of Contracts, Fiscal Year Maturity [Abstract]
Life settlement contracts, fair value method, number of contracts, maturing in next twelve months	63
Life settlement contracts, fair value method, number of contracts, maturing in year two	55
Life settlement contracts, fair value method, number of contracts, maturing in year three	49
Life settlement contracts, fair value method, number of contracts, maturing in year four	43
Life settlement contracts, fair value method, number of contracts, maturing in year five	36
Life settlement contracts, fair value method, number of contracts, maturing after year five	280
Life settlement contracts, fair value method, number of contracts	526
Life settlement contracts, fair value, maturing in next twelve months	$ 10
Life settlement contracts, fair value, maturing in year two	8
Life settlement contracts, fair value, maturing in year three	7
Life settlement contracts, fair value, maturing in year four	6
Life settlement contracts, fair value, maturing in year five	4
Life settlement contracts, fair value, maturing after year five	23
Life settlement contracts, fair value	58	$ 74
Life settlement contracts, fair value method, face value, maturing in next twelve months	34
Life settlement contracts, fair value method, face value, maturing in year two	30
Life settlement contracts, fair value method, face value, maturing in year three	26
Life settlement contracts, fair value method, face value, maturing in year four	23
Life settlement contracts, fair value method, face value, maturing in year five	19
Life settlement contracts, fair value method, face value, maturing after year five	153
Life settlement contracts, fair value method, face value	$ 285