Unaudited Condensed Consolidated Statements of Comprehensive Income Parenthetical (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Unrealized gain on derivative instruments, tax				$ 229
Reclassifications to net income:
Hedging gain realized, tax	5	61	10	70
Post-retirement negative prior service cost, tax	513	506	1,026	1,012
Unrealized loss on derivative instruments, tax				1,427
Pension actuarial loss, net of tax of $988 and $1,976 for the three and six month periods in 2012 and $246 and $492 for the three and six month periods in 2011 [Member]
Reclassifications to net income:
Actuarial loss, tax	988	246	1,976	492
Post-retirement actuarial loss, net of tax of $40 and $80 for the three and six month periods in 2012 and $48 and $96 for the three and six month periods in 2011 [Member]
Reclassifications to net income:
Actuarial loss, tax	$ 40	$ 48	$ 80	$ 96