Employee Benefit Plans - Components of Expense (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Net periodic benefit cost	$ 4,780	$ 3,317	$ 9,594	$ 7,925
Continuing Operations
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Net periodic benefit cost	4,659	3,233	9,268	7,735
Disposed of by sale | Discontinued Operations
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Net periodic benefit cost	121	84	326	190
Defined contribution plans
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Net periodic benefit cost	3,702	1,695	7,481	4,690
Multi-employer plans
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Net periodic benefit cost	52	58	61	99
Defined benefit plans
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Interest cost	4,918	5,800	9,835	11,600
Expected return on plan assets, net of expenses	(5,256)	(5,058)	(10,512)	(10,116)
Amortization of actuarial loss and prior service cost	1,124	572	2,249	1,144
Total for defined benefit pension plan	786	1,314	1,572	2,628
SERPs
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Net periodic benefit cost	$ 240	$ 250	$ 480	$ 508