Employee Benefit Plans - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Retirement Benefits [Abstract]
Percentage contribution by participant to the 401(k) Plan, maximum	75.00%
Employer contribution of first specific employee contribution percentage	100.00%
Employee contribution used to determine employer first contribution	3.00%
Employer contribution of next specific employee contribution percentage	50.00%
Employee contribution used to determine employer next contribution	2.00%
Company's contribution cost recognized	$ 2,700	$ 2,500	$ 1,800
Postemployment benefits liabilities, noncurrent	2,060	1,678
Expense recorded in connection of postemployment benefit plans	$ 0	$ 0	$ 0