Employee Benefit Plans (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Pension Benefits
Components of the net periodic benefit cost
Service cost	$ 0	$ 0	$ 0	$ 0
Interest cost	1,057	1,124	3,171	3,372
Expected return on plan assets	(1,751)	(1,536)	(5,254)	(4,609)
Recognized net actuarial loss	382	374	1,147	1,123
Benefit cost (income)	(312)	(38)	(936)	(114)
Postretirement Benefits
Components of the net periodic benefit cost
Service cost	210	188	631	564
Interest cost	342	329	1,025	989
Amortization of prior service cost	(136)	(135)	(408)	(407)
Recognized net actuarial loss	368	320	1,105	960
Benefit cost (income)	$ 784	$ 702	$ 2,353	$ 2,106