Lease Obligations - Additional information (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2019	Jan. 01, 2019	Dec. 31, 2018
Operating And Finance Leases [Line Items]
Additional right of use lease assets	$ 22,968		$ 0
Long-term finance and operating lease obligations	$ 17,084		0
Option to extend lease term (up to)	5 years
Option to terminate leases, period	1 year
Minimum lease payments required	$ 27,501
Leased assets capitalized			2,600
Capital lease obligations classified as current			1,100
Capital lease obligations outstanding			$ 2,700
Subsidiaries [Member] | Employees [Member]
Operating And Finance Leases [Line Items]
Minimum lease payments required	$ 4,800
Lease amortization period	4 years 9 months 18 days
Minimum [Member]
Operating And Finance Leases [Line Items]
Remaining lease term	1 year
Maximum [Member]
Operating And Finance Leases [Line Items]
Remaining lease term	8 years
Accounting Standards Update 2016-02 [Member]
Operating And Finance Leases [Line Items]
Additional right of use lease assets		$ 15,100
Long-term finance and operating lease obligations		$ 15,100