Employee Benefit Plans (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Components of the net periodic pension and postretirement benefit cost
Service cost	$ 192	$ 176	$ 576	$ 528
Interest cost	1,750	1,904	5,250	5,712
Expected return on assets	(2,464)	(2,514)	(7,392)	(7,542)
Amortization of prior service cost	81	81	243	243
Amortization of actuarial loss	149	57	447	171
Net periodic pension and postretirement benefit	$ (292)	$ (296)	$ (876)	$ (888)