Leases - Components of Lease Expense (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2019 USD ($)
Operating lease costs
Single lease costs	$ 1,046
Variable lease costs	419
Sublease income:
Single sublease income	(328)
Variable sublease income	(139)
Total operating lease costs	998
Finance lease costs:
Amortization of right-of-use assets	115
Interest on lease liabilities	18
Total finance lease costs	$ 133