Income Taxes (Deferred Tax Liabilities (Assets)) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Depreciation	$ 9,563	$ 17,367
Goodwill	32,662	43,562
Intangible assets	10,928	14,731
Foreign withholding tax	1,014	0
Other	652	892
Gross deferred tax liabilities	54,819	76,552
Equity compensation	(12,577)	(21,439)
Other	(13,247)	(18,473)
Gross deferred tax assets	(25,824)	(39,912)
Valuation allowances	2,242	1,362
Deferred tax assets, net of valuation allowances	(23,582)	(38,550)
Net deferred tax liabilities	$ 31,237	$ 38,002