Summary of Investments - SOI AFS Proceeds from sales (Details 2.1) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Investments, Debt and Equity Securities [Abstract]
Proceeds from sales	$ 1,673,307	$ 337,206	$ 3,356,200	$ 2,995,877
Gross realized gains from sales	26,810	8,584	46,667	31,935
Gross realized losses from sales	$ 135	$ 304	$ 146	$ 324