Employee Benefit Plans (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014		Mar. 31, 2013
Defined Benefit Plan Disclosure [Line Items]
Number of Union Pension Plans	2
Pension Benefits
Components of net periodic benefit costs:
Service cost	$ 3,352		$ 3,576
Interest cost	1,659		1,350
Expected return on plan assets	(1,697)		(1,470)
Amortization of prior service cost (credit)(1)	33	[1]	77	[1]
Amortization of actuarial loss(1)	629	[1]	1,022	[1]
Net periodic benefit cost (credit)	3,976		4,555
Other Post-Retirement Benefits
Components of net periodic benefit costs:
Service cost	67		77
Interest cost	114		115
Expected return on plan assets	0		0
Amortization of prior service cost (credit)(1)	(928)	[1]	(928)	[1]
Amortization of actuarial loss(1)	195	[1]	308	[1]
Net periodic benefit cost (credit)	$ (552)		$ (428)

[1] (1) These amounts are included in our Consolidated Statements of Comprehensive Income and Consolidated Statements of Cash Flows as changes in employee benefit plan assets and benefit obligat