Leases - Supplemental Cash flow Information to operating leases (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2019	Dec. 31, 2018
Supplemental cash flow information
Cash paid for amounts included in the measurement of operating lease liabilities	$ 4,242
Operating ROU assets obtained in exchange for lease liabilities	388
Supplemental balance sheet information
Operating lease ROU assets	42,571	$ 0
Operating lease liabilities:
Accrued expenses and other current liabilities	6,857
Operating lease liabilities	37,056	$ 0
Total operating lease liabilities	$ 43,913