Employee Benefits - Additional Information (Details)			1 Months Ended	12 Months Ended
	Sep. 07, 2018 USD ($)	Dec. 19, 2017 USD ($) retiree	Dec. 31, 2017 USD ($)	Dec. 31, 2019 USD ($) transfer	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Defined Benefit Plan Disclosure [Line Items]
Number of consecutive years of employee's compensation				5 years
Number of total years of employee's compensation				10 years
Service cost				$ 0
Expected long-term rate of return on plan assets				4.80%	7.50%	7.50%
Employer contributions	$ 20,400,000			$ 0	$ 20,420,000
Return to provision discrete tax benefit			$ 2,900,000
Net actuarial loss included in accumulated other comprehensive losses expected to be recognized				1,500,000
Future prior service credit to be recognized due to freeze of accrual benefits				0
Accumulated benefit obligation				113,700,000	95,200,000
Number of retirees covered by annuity contract | retiree		124
Number of retirees covered by annuity contract receiving death benefits | retiree		30
Defined benefit obligations, death benefits		$ 2,000
Total premium paid out of plan's assets		$ 1,500,000		6,282,000	7,975,000
Projected benefit obligation			106,664,000	113,679,000	95,200,000	$ 106,664,000
Net periodic benefit cost				$ 867,000	(250,000)	(347,000)
Transfers of plan assets between levels 1 and 2 on recurring basis					2,200,000
Number of transfers | transfer				0
Purchases of level 3 plan assets				$ 0	0
Transfers of level 3 plan assets				0	0
Required cash contributions to the plan				100,000
Supplemental Executive Retirement Plan
Defined Benefit Plan Disclosure [Line Items]
Projected benefit obligation				5,300,000	4,400,000
Net periodic benefit cost				400,000	500,000	500,000
Amounts before tax reflected in accumulated other comprehensive income (loss)			$ 2,700,000	$ 2,400,000	1,900,000	2,700,000
Thrift Plan
Defined Benefit Plan Disclosure [Line Items]
Contributions to the Thrift Plan				3.50%
Compensation expense				$ 2,000,000.0	$ 1,700,000	$ 1,800,000
Total equity securities | Minimum
Defined Benefit Plan Disclosure [Line Items]
Targeted asset allocation percentage				5.00%	50.00%
Total equity securities | Maximum
Defined Benefit Plan Disclosure [Line Items]
Targeted asset allocation percentage				15.00%	70.00%
Fixed income | Minimum
Defined Benefit Plan Disclosure [Line Items]
Targeted asset allocation percentage				85.00%	30.00%
Fixed income | Maximum
Defined Benefit Plan Disclosure [Line Items]
Targeted asset allocation percentage				95.00%	50.00%