Employee Benefit Plans - Components of Expense (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Net periodic benefit cost	$ 5,577	$ 6,518	$ 11,258	$ 12,690
Allocated to discontinued operations	0	0	0	(1,096)
Net periodic benefit cost — continuing operations	5,577	6,518	11,258	11,594
Defined contribution plans
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Net periodic benefit cost	2,086	2,360	4,274	5,711
Multi-employer plans
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Net periodic benefit cost	42	38	85	97
Defined benefit plans
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Interest cost	6,770	8,179	13,540	14,628
Expected return on plan assets, net of expenses	(4,599)	(6,624)	(9,196)	(11,709)
Amortization of actuarial loss	997	1,204	1,995	2,336
Defined Benefit Plan, Curtailments	0	1,080	0	1,080
Total for defined benefit plans	3,168	3,839	6,339	6,335
SERP
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Net periodic benefit cost	$ 281	$ 281	$ 560	$ 547