Employee Benefit Plans - Narrative (Details)	12 Months Ended
	Dec. 31, 2018 USD ($) Retiree shares	Dec. 31, 2017 USD ($) Retiree employee shares	Dec. 31, 2016 USD ($)
Defined Benefit Plan Disclosure [Line Items]
Number of retirees and dependents | Retiree	337	340
Subsidy limit percentage of expected annual fully insured premium over age threshold	60.00%
Subsidy limit percentage of expected annual fully insured premium under age threshold	$ 648,000
Annual subsidy limit percentage increases for fully insured premium over age threshold	3.50%
Estimated contributions next year	$ 1,900,000
Liabilities, including the Company's common stock	25,780,000	$ 29,145,000
Defined contribution cost (credit) recognized	$ 3,100,000	2,600,000	$ 1,800,000
Savings Investment Plan
Defined Benefit Plan Disclosure [Line Items]
Employer matching percent	6.00%
Maximum contribution, percent of employee salary	10.00%
Plan contributions charged to expense	$ 5,900,000	6,500,000	6,500,000
Deferred compensation plan
Defined Benefit Plan Disclosure [Line Items]
Market value of the trust assets, excluding the Company's common stock	14,700,000	15,000,000
Liabilities, including the Company's common stock	$ 25,800,000	$ 29,100,000
Number of common stock deferred into the rabbi trust (in shares) | shares	495,774	495,774
Company's common stock held in the rabbi trust	$ 5,100,000	$ 5,100,000
Company contributions to deferred compensation plan	$ 1,100,000	$ 1,000,000	$ 600,000
West Virginia, Virginia, and Ohio
Defined Benefit Plan Disclosure [Line Items]
Employees terminated | employee		100