Certain Long-Duration Contracts With Guarantees (Separate Account Investment Options) (Details) - Variable Annuity Contracts - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Separate Account Investment Options	$ 130,259,024	$ 38,985,863
Equity funds
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Separate Account Investment Options	77,133,820	24,639,438
Bond funds
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Separate Account Investment Options	44,025,867	12,264,741
Money market funds
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Separate Account Investment Options	$ 9,099,337	$ 2,081,684