Leases - Cost and Accumulated Depreciation (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2019	Dec. 31, 2018
Future minimum rental payments under noncancelable leases
Remainder of 2019	$ 5,360	$ 5,360
2020			$ 8,668
2021			7,961
2022			5,101
2023			2,632
Thereafter			34,638
Office space leased in headquarters office and to third party lessees
Future minimum rental income from related parties		$0.1 million and $0.2 million, respectively
Third party lessees
Office space leased in headquarters office and to third party lessees
Cost	288,700	$ 288,700	289,200
Buildings
Office space leased in headquarters office and to third party lessees
Accumulated Depreciation	137,400	137,400	$ 133,700
Related parties associated with its branch premises
Lease payments to related parties	100	200
Future minimum rental payments under noncancelable leases
Remainder of 2019	200	200
2020	300	300
2021	300	300
2022	200	200
2023	200	200
Thereafter	$ 7,500	$ 7,500