Summary of Investments - SOI AFS Proceeds from sales (Details 2.1) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Investments, Debt and Equity Securities [Abstract]
Proceeds from sales	$ 192,100	$ 118,810	$ 3,187,977	$ 2,418,114
Gross realized gains from sales	6,632	7,196	38,567	29,434
Gross realized losses from sales	$ 478	$ 0	$ 802	$ 1,090