Leases - Narrative (Details) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2019 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Operating Leased Assets [Line Items]
Rent expense			$ 4,900	$ 4,200
Impairment of ROU asset	$ 800
Short-term lease costs		$ 1,300
Number of operating leases not yet commenced	1	1
Initial lease liability of operating leases that have not yet commenced	$ 1,600	$ 1,600
Term of operating lease that has not yet commenced	5 years	5 years
Liability related to rent escalations			1,100
Allowance for moving expenses and tenant improvements			1,800
Operating lease right-of-use assets	$ 19,826	$ 19,826
Prepaid lease assets, remaining amortization period	4 years 3 months 18 days	4 years 3 months 18 days
Net book value of asset	$ 90,732	$ 90,732	$ 95,840
Minimum
Operating Leased Assets [Line Items]
Recognition period for rent expense			48 months
Maximum
Operating Leased Assets [Line Items]
Recognition period for rent expense			125 months
Yangzhou
Operating Leased Assets [Line Items]
Operating lease right-of-use assets	$ 2,400	$ 2,400
Prepaid lease assets, remaining amortization period	39 years	39 years
Yangzhou | Buildings on Prepaid Land
Operating Leased Assets [Line Items]
Net book value of asset	$ 17,100	$ 17,100
Remaining depreciable period of asset		20 years
Property Subject to Rent Escalations | Maximum
Operating Leased Assets [Line Items]
Lessee term of contract	41 years	41 years