Leases - Supplemental Cash flow Information to operating leases (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Dec. 31, 2018
Supplemental cash flow information
Cash paid for amounts included in the measurement of operating lease liabilities	$ 2,118
Operating ROU assets obtained in exchange for lease liabilities	388
Supplemental balance sheet information
Operating lease ROU assets	44,251	$ 0
Operating lease liabilities:
Accrued expenses and other current liabilities	6,859
Operating lease liabilities	38,764	$ 0
Total operating lease liabilities	$ 45,623