Commitments and Contingencies - Other Information Related to Leases (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Commitments and Contingencies Disclosure [Abstract]
Cash paid for amounts included in the measurement of lease liabilities, operating cash flows from operating leases	$ 10,765	$ 10,027	$ 8,345
Cash paid for amounts included in the measurement of lease liabilities, operating cash flows from finance leases	482	591	885
Cash paid for amounts included in the measurement of lease liabilities, financing cash flows from finance leases	9,220	10,032	12,968
Right-of-use assets obtained in exchange for lease obligations, operating leases	3,411	7,276	5,913
Right-of-use assets obtained in exchange for new finance lease liabilities	$ 15,370	$ 862	$ 14,875
Weighted average remaining lease term (years), operating leases	3 years 5 months 4 days	3 years 11 months 26 days	4 years 3 months 10 days
Weighted average remaining lease term (years), finance leases	3 years 4 months 13 days	2 years 21 days	2 years 9 months 29 days
Weighted average discount rate, operating leases	4.30%	4.10%	3.90%
Weighted average discount rate, finance leases	4.30%	3.10%	3.00%