Employee Benefit Plans - Pension Plan Funded Status (Details) - Pension Plan - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Pension Plan Description
Requisite age of employees to be eligible for participation	21 years
Requisite number of hours worked to be eligible for participation	1,000
Term of treasury note used to determine rate credited to participants' accounts	5 years
Basis spread on variable base rate used to calculate interest on participants' accounts balance (as a percent)	0.25%
Monthly interest credit cap	0.12
Weighted-average interest crediting rate	2.25%	1.50%
Percent participant accounts are vested	100.00%
Change in benefit obligation:
Benefit obligation, beginning of period	$ 31,389	$ 33,174
Interest cost on benefit obligation	983	1,138	$ 1,281
Actuarial (gain) loss	(630)	765
Benefits paid	(3,412)	(3,688)
Benefit obligation, end of period	28,330	31,389	33,174
Change in fair value of plan assets:
Fair value of plan assets, beginning of period	36,863	39,377
Actual gain (loss) on plan assets	(607)	1,174
Benefits paid	(3,412)	(3,688)
Fair value of plan assets, end of period	32,844	36,863	$ 39,377
Funded status of plan, end of period	4,514	5,474
Amounts recognized in the Consolidated Statements of Financial Condition:
Prepaid benefit cost, end of period	4,514	5,474
Benefit obligation:
Accumulated benefit obligation	$ 28,300	$ 31,400
Discount rate used to determine the projected benefit obligation	3.95%	3.30%
Average estimated duration of benefit cash flows	6 years 7 months 2 days