Income Taxes - Schedule of Components of Company's Net Deferred Tax Asset (Liability) (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Deferred tax assets:
Accrued liabilities	$ 18,670	$ 17,563
Depreciation and amortization	872	980
Foreign operating loss carryforward	248	246
U.S. federal tax credits and carryforward	0	8,152
U.S. state and local tax credits and carryforward	223	1,799
Other	41	667
Valuation allowance	(169)	(2,394)
Total deferred tax assets	19,885	27,013
Deferred tax liabilities:
Depreciation and amortization	(18,803)	(20,117)
Prepaid expenses	(550)	(572)
Other	(258)	(541)
Total deferred tax liabilities	(19,611)	(21,230)
Net deferred tax asset	$ 274	$ 5,783