Consolidated Statements of Comprehensive Income (Parenthetical) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Amortization of net obligation at transition, tax	$ (1)	$ 26	$ 6	$ 77
Amortization of prior service cost, tax	26	28	78	82
Amortization of net loss, including settlement charges, tax	500	729	4,071	2,383
Current period change in fair value of pension, tax	190	2,238	(962)	2,238
Commodity contracts
Current period change in fair value of interest rate swap, tax	18	42	25	(6,669)
Reclassification adjustment for derivative instruments, tax	(2,277)	(3,205)	(5,997)	(11,486)
Interest rate swap
Current period change in fair value of interest rate swap, tax	0	(188)	(160)	(23)
Reclassification adjustment for derivative instruments, tax	$ 86	$ 156	$ 798	$ 449