Commitments and Contingencies - Other Information Related to Leases (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Commitments and Contingencies Disclosure [Abstract]
Cash paid for amounts included in the measurement of lease liabilities, operating cash flows from operating leases	$ 2,600	$ 2,523
Cash paid for amounts included in the measurement of lease liabilities, operating cash flows from finance leases	109	179
Cash paid for amounts included in the measurement of lease liabilities, financing cash flows from finance leases	2,159	2,802
Right-of-use assets obtained in exchange for lease obligations, operating leases	$ 1,117	$ 3,360
Weighted average remaining lease term (years), operating leases	3 years 10 months 24 days	4 years 3 months 22 days
Weighted average remaining lease term (years), finance leases	1 year 10 months 14 days	2 years 7 months 10 days
Weighted average discount rate, operating leases	4.10%	4.00%
Weighted average discount rate, finance leases	3.10%	3.00%