Leases (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Jan. 01, 2019	Dec. 31, 2018
Lessee, Lease, Description [Line Items]
Operating Leases, Rent Expense	$ 11,036	$ 10,117
Operating Lease, Payments	2,973
Operating Lease, Incentive Payments Received	6,198
Operating Lease Right-of-Use Assets	187,029			$ 0
Lessee, Additional Payments for Operating Leases Not Yet Commenced	252,300
Letter of Credit [Member]
Lessee, Lease, Description [Line Items]
Other Assets	5,509			$ 5,502
Office Equipment [Member]
Lessee, Lease, Description [Line Items]
Operating Leases, Rent Expense	$ 923	$ 459
Minimum [Member]
Lessee, Lease, Description [Line Items]
Lessee, Operating Lease, Lease Not yet Commenced, Term of Contract	7 years
Maximum [Member]
Lessee, Lease, Description [Line Items]
Lessee, Operating Lease, Lease Not yet Commenced, Term of Contract	15 years
Accounting Standards Update 2016-02 [Member]
Lessee, Lease, Description [Line Items]
Operating Lease Right-of-Use Assets			$ 180,935