Leases - Components of Lease Expense (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2019
Operating lease costs
Single lease costs	$ 1,039	$ 3,141
Variable lease costs	410	1,310
Sublease income:
Single sublease income	(329)	(986)
Variable sublease income	(139)	(417)
Total operating lease costs	981	3,048
Finance lease costs:
Amortization of right-of-use assets	106	328
Interest on lease liabilities	11	43
Total finance lease costs	$ 117	$ 371