Subsequent Events (Details) - USD ($) $ in Thousands	Jan. 26, 2017	Jan. 04, 2017	Dec. 31, 2016	Jan. 21, 2016	Dec. 31, 2015	Dec. 31, 2014
Subsequent Event [Line Items]
Other invested assets			$ 1,591,940		$ 1,298,120
Stock Repurchase Program, Authorized Amount			$ 400,000	$ 400,000	$ 450,000	$ 300,000
Subsequent Event [Member]
Subsequent Event [Line Items]
Other invested assets		$ 53,100
Stock Repurchase Program, Authorized Amount	$ 400,000