Employee Benefit Plans - Funded Status of the Postretirement Plan (Details) - Postretirement Plan - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Change in benefit obligation:
Benefit obligation, beginning of period	$ 3,717	$ 4,164
Interest cost on benefit obligation	110	133	$ 151
Actuarial (gain) loss	(115)	(248)
Benefits paid	(392)	(332)
Benefit obligation, end of period	3,320	3,717	4,164
Change in fair value of plan assets:
Fair value of plan assets, beginning of period	0	0
Benefits paid	(392)	(332)
TCF contributions	392	332	300
Fair value of plan assets, end of period	0	0	$ 0
Funded status of plan, end of period	(3,320)	(3,717)
Amounts recognized in the Consolidated Statements of Financial Condition:
Prepaid (accrued) benefit cost, end of period	(3,320)	(3,717)
Prior service cost included in accumulated other comprehensive income (loss)	$ (147)	$ (193)