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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

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