Minimum Guarantees - Fair Value of Equity Securities Supporting Separate Accounts (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Fair value of assets supporting separate accounts	$ 468,582	$ 265,825
GMDB
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Fair value of assets supporting separate accounts	55,605	55,997
GLWB
Schedule of Fair Value of Separate Accounts by Major Category of Investment [Line Items]
Fair value of assets supporting separate accounts	$ 412,977	$ 209,828