Right-of-Use ("ROU") Assets and Lease Liabilities - Lease Cost (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2019 USD ($)
Operating leases:
Lease cost	$ 8,052
Variable lease cost	1,053
Operating lease cost	9,105
Finance leases:
Amortization of ROU assets	668
Interest on lease liabilities	124
Finance lease cost	792
Total lease cost	9,897
Cash paid for amounts included in the measurement of lease liabilities:
Operating cash flows from operating leases	6,618
Financing cash flows from finance leases	654
Right-of-use-assets obtained in exchange for lease obligations:
Finance leases	185
Operating leases	$ 120,555
Operating Leases
Weighted average remaining lease term (years)	5 years 6 months 18 days
Weighted average discount rate	4.60%
Finance Leases
Weighted average remaining lease term (years)	5.20%
Weighted average discount rate	3 years 10 months 21 days