Pension and Other Post Retirement Benefit Plans - Narrative (Details) - USD ($)		12 Months Ended
	Mar. 01, 2005	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Defined Benefit Plan Disclosure [Line Items]
Percentage of employees covered by plan		10.00%
Minimum participant attained age	55 years
Requisite service period (at least)	10 years
Accumulated benefit obligation		$ 76,770,000	$ 73,193,000
Minimum required contribution in next fiscal year		$ 0
Requisite service period		1000 hours
Employer percentage contribution		2.00%
Vesting period		5 years
Expense recognized in the period		$ 4,560,000	5,114,000	$ 3,691,000
Fair value of plan assets		85,121,000	76,736,000	85,213,000
Net periodic pension benefit cost		(909,000)	(1,693,000)	654,000
Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		80,689,000	71,277,000
Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets		$ 4,432,000	$ 5,459,000
Contribution for first 3%
Defined Benefit Plan Disclosure [Line Items]
Amount of discretionary contributions made by employer to defined contribution plan, percent		100.00%
Maximum annual contribution percentage per employee		3.00%
Contribution after first 3%
Defined Benefit Plan Disclosure [Line Items]
Amount of discretionary contributions made by employer to defined contribution plan, percent		50.00%
Maximum annual contribution percentage per employee		3.00%
Minimum | Debt securities
Defined Benefit Plan Disclosure [Line Items]
Maturities of debt securities		15 days	15 days
Maximum | Debt securities
Defined Benefit Plan Disclosure [Line Items]
Maturities of debt securities		7 years 8 months 1 day	8 years 2 months 26 days
Weighted Average | Debt securities
Defined Benefit Plan Disclosure [Line Items]
Maturities of debt securities		4 years	4 years 3 months 14 days
MBT
Defined Benefit Plan Disclosure [Line Items]
Post retirement plan expense		$ (43,000)
Defined Benefit Plan, Benefit Obligation		$ 4,000,000.0
MBT | Minimum
Defined Benefit Plan Disclosure [Line Items]
Age of plan participants		55 years
Requisite service period (at least)		5 years
MBT | Maximum
Defined Benefit Plan Disclosure [Line Items]
Age of plan participants		65 years
Non-qualified plans
Defined Benefit Plan Disclosure [Line Items]
Net periodic pension benefit cost		$ 192,000	$ 161,000	$ 213,000