Employee Benefit Plans (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Pension Benefits
Components of the net periodic benefit cost
Service cost	$ 43	$ 0
Interest cost	1,162	1,065
Expected return on plan assets	(1,905)	(1,755)
Recognized net actuarial loss	207	392
Benefit cost (income)	(493)	(298)
Postretirement Benefits
Components of the net periodic benefit cost
Service cost	187	224
Interest cost	393	346
Amortization of prior service cost	(136)	(136)
Recognized net actuarial loss	229	359
Benefit cost (income)	$ 673	$ 793