Income Taxes (Provision for Income Taxes) (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Current tax expense:
Federal		$ 1,744	$ 312	$ 4,208
State		2,101	159	1,238
Foreign		9,421	7,111	6,949
Current income tax expense (benefit)		13,266	7,582	12,395
Deferred income tax expense (benefit)		(40,021)	(2,871)	2,251
Provision (benefit) for income taxes		(26,755)	$ 4,711	$ 14,646
Income tax benefit, 2017 Tax Cuts and Jobs Act	$ 31,900	$ 31,900