Condensed Consolidated Statements Of Comprehensive Income (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Net income	$ 7,265	$ 7,963
Other comprehensive income (loss), net of tax:
Total other comprehensive income, net	1,585	587
Comprehensive income	8,850	8,550
Defined Benefit Pension Plans: [Member]
Other comprehensive income (loss), net of tax:
Amortization of prior service cost/credit	186	186
Amortization of net actuarial losses	2,682	1,551
Other Postretirement Benefit Plans: [Member]
Other comprehensive income (loss), net of tax:
Amortization of prior service cost/credit	(2,442)	(2,441)
Amortization of net actuarial losses	$ 1,159	$ 1,291