Employee Benefit Plans - Components of Expense (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Net periodic benefit cost	$ 4,189	$ 4,926	$ 17,484	$ 15,981
Defined benefit plans
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Service cost	21	17	64	51
Interest cost	6,600	5,976	19,155	17,927
Expected return on plan assets, net of expenses	(5,893)	(5,371)	(17,611)	(16,113)
Amortization of actuarial loss	862	1,060	2,145	3,182
Total for defined benefit plans	1,590	1,682	3,753	5,047
Multi-employer plans
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Net periodic benefit cost	100	95	324	326
Withdrawal from GCIU multi-employer plan
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Net periodic benefit cost	0	0	4,100	0
SERP
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Net periodic benefit cost	80	808	672	1,981
Defined contribution plans
Defined Benefit Plan, Net Periodic Benefit Cost [Abstract]
Net periodic benefit cost	$ 2,419	$ 2,341	$ 8,635	$ 8,627