Investment Securities (Details 4) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Realized gains (losses) on marketable investment securities
Proceeds from sales of available-for-sale marketable investment securities	$ 4,000	$ 36,900	$ 94,200	$ 42,300
Fair value of marketable investment securities in a loss position
Less than 12 months	485,186		485,186		$ 968,941
12 months or more	135,389		135,389
Total	620,575		620,575		968,941
Unrealized losses on marketable investment securities in a loss position
Less than 12 months	(3,751)		(3,751)		(4,929)
12 months or more	(85)		(85)
Total	$ (3,836)		$ (3,836)		$ (4,929)