Investment Securities (Details 4) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Fair Value
Less than 12 months	$ 271,067		$ 271,067		$ 364,160
12 months or more	1,564		1,564		149,889
Total	272,631		272,631		514,049
Unrealized Losses
Less than 12 months	(973)		(973)		(609)
12 months or more	(8)		(8)		(126)
Total	(981)		(981)		$ (735)
Sales of Marketable Investment Securities
Gains from sales of available-for-sale securities			5,600
Proceeds from sales of available-for-sale securities	$ 4,000	$ 4,000	$ 35,800	$ 94,200