Investments (Details 6) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Asset derivatives:
Derivatives Asset, Net Amount	$ 9,932	$ 8,694
Free-standing derivatives [Member]
Asset derivatives:
Derivatives Asset, Gross Amounts	9,932	8,694
Derivatives Asset, Gross Amounts Offset in the Consolidated Balance Sheets	0	0
Derivatives Asset, Net Amounts of Assets/Liabilities Presented in the Consolidated Balance Sheets	9,932	8,694
Derivatives Asset, Gross Amounts Not Offset in the Consolidated Balance Sheet, Financial Instruments	0	0
Derivatives Asset, Gross Amounts Not Offset in the Consolidated Balance Sheet, Cash Collateral Received	10,449	8,824
Derivatives Asset, Net Amount	$ (517)	$ (130)