Employee Benefit Plans - Components of Expense (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Net periodic benefit cost	$ 8,638	$ 5,587	$ 13,295	$ 11,055
Defined benefit plans
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Service cost	22	17	43	34
Interest cost	6,277	5,975	12,555	11,951
Expected return on plan assets, net of expenses	(5,859)	(5,371)	(11,718)	(10,742)
Amortization of actuarial loss	641	1,061	1,283	2,122
Total for defined benefit plans	1,081	1,682	2,163	3,365
Multi-employer plans
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Net periodic benefit cost	105	111	224	231
Withdrawal from GCIU multi-employer plan
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Net periodic benefit cost	4,100	0	4,100	0
SERP
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Net periodic benefit cost	296	887	592	1,173
Defined contribution plans
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Net periodic benefit cost	$ 3,056	$ 2,907	$ 6,216	$ 6,286