Income Taxes (Details 1) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Federal:
Current	$ 44,921	$ 57,321	$ 66,973
Deferred	(46,938)	18,704	15,528
State:
Current	3,774	4,636	5,165
Deferred	3,921	1,878	1,768
Foreign:
Current	2,929	4,187	4,150
Deferred	(3,046)	(6,420)	(5,412)
Provision for income taxes	$ 5,561	$ 80,306	$ 88,172