Employee Benefit Plans - Components of Expense (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Net periodic benefit cost	$ 4,336	$ 4,818	$ 13,930	$ 12,743
Continuing Operations
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Net periodic benefit cost	4,165	4,715	13,433	12,450
Disposed of by sale | Discontinued Operations
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Net periodic benefit cost	171	103	497	293
Defined contribution plans
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Net periodic benefit cost	3,060	2,743	10,541	7,433
Multi-employer plans
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Net periodic benefit cost	15	4	76	103
Defined benefit plans
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Interest cost	5,014	5,865	14,849	17,465
Expected return on plan assets, net of expenses	(5,250)	(4,865)	(15,762)	(14,981)
Amortization of actuarial loss and prior service cost	1,255	823	3,504	1,967
Total for defined benefit pension plan	1,019	1,823	2,591	4,451
SERPs
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Net periodic benefit cost	$ 242	$ 248	$ 722	$ 756