Unaudited Condensed Consolidated Statements of Comprehensive Income (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
NET INCOME	$ 11,059	$ 12,299	$ 17,491	$ 15,063
OTHER COMPREHENSIVE INCOME:
Unrealized gain on derivative instruments, net of tax of $229 for the six month period in 2011	0	0	0	402
Reclassifications to net income:
Hedging gain realized, net of tax of $5 and $10 for the three and six month periods in 2012 and $61 and $70 for the three and six month periods in 2011.	(9)	(107)	(18)	(123)
Post-retirement negative prior service cost, net of tax of $513 and $1,026 for the three and six month periods in 2012 and $506 and $1,012 for the three and six month periods in 2011.	(874)	(882)	(1,748)	(1,764)
Unrealized loss on derivative instruments, net of tax of $1,427 for the six month period in 2011	0	0	0	2,505
TOTAL OTHER COMPREHENSIVE INCOME (LOSS)	867	(476)	1,734	2,046
TOTAL COMPREHENSIVE INCOME	11,926	11,823	19,225	17,109
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, net of tax	1,682	429	3,364	858
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, net of tax	$ 68	$ 84	$ 136	$ 168