Unaudited Condensed Consolidated Statements of Comprehensive Income Parenthetical (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Unrealized gain on derivative instruments, tax				$ 229
Reclassifications to net income:
Hedging gain realized, tax	5	6	16	76
Post-retirement negative prior service cost, tax	514	506	1,541	1,518
Unrealized loss on derivative instruments, tax				1,427
Pension actuarial loss, net of tax of $988 and $2,964 for the three and nine month periods in 2012 and $246 and $738 for the three and nine month periods in 2011 [Member]
Reclassifications to net income:
Actuarial loss, tax	988	246	2,964	738
Post-retirement actuarial loss, net of tax of $40 and $120 for the three and nine month periods in 2012 and $40 and $136 for the three and nine month periods in 2011 [Member]
Reclassifications to net income:
Actuarial loss, tax	$ 40	$ 40	$ 120	$ 136