Pension and Other Postretirement Benefits (Details) (USD $) In Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Pension Benefits
Components of net periodic benefit cost:
Service cost	$ 1,291	$ 1,105	$ 3,873	$ 3,315
Interest cost	3,144	3,226	9,432	9,678
Expected return on plan assets	(3,929)	(3,269)	(11,787)	(9,807)
Amortization of prior service cost (credit)	68	76	204	228
Amortization of net actuarial loss	2,063	2,231	6,189	6,693
Settlement loss			1,716
Net periodic benefit cost	2,637	3,369	9,627	10,107
Other Benefits
Components of net periodic benefit cost:
Service cost	1,827	753	4,333	2,259
Interest cost	6,206	6,510	18,686	19,522
Amortization of prior service cost (credit)	(240)	(524)	(720)	(1,572)
Amortization of net actuarial loss	1,971	3,630	8,075	10,890
Net periodic benefit cost	$ 9,764	$ 10,369	$ 30,374	$ 31,099