Summary of Investments (Details 2.1) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Investments, Debt and Equity Securities [Abstract]
Proceeds from sales	$ 118,810	$ 2,661,364	$ 2,418,114	$ 8,022,277
Gross realized gains from sales	7,196	11,061	29,434	62,465
Gross realized losses from sales	$ 0	$ 2	$ 1,090	$ 26,914