Income Taxes - Current and Long-Term Deferred Tax Assests and Liabilities (Details 4) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Non-current deferred tax assets	$ 20,694	$ 45,839
Non-current deferred tax liabilities	(3,802)	(2,367)
Total net deferred tax assets	16,892	43,472
Total net deferred tax assets	$ 16,892	$ 43,472