Summary of Investments - SOI AFS Proceeds from sales (Details 2.1) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Investments, Debt and Equity Securities [Abstract]
Proceeds from sales	$ 421,245	$ 192,100	$ 3,777,445	$ 3,187,977
Gross realized gains from sales	8,487	6,632	55,154	38,567
Gross realized losses from sales	$ 24	$ 478	$ 170	$ 802