Consolidated Condensed Statements of Comprehensive Income (Parenthetical) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Amortization of net obligation at transition, tax	$ 3	$ 26
Amortization of prior service cost, tax	26	27
Amortization of net loss, including settlement charges, tax	2,994	920
Derivative commodity instruments
Current period change in fair value of derivative, tax	1	(16,424)
Reclassification adjustment for derivative instruments, tax	(1,541)	(6,570)
Interest rate swap
Current period change in fair value of derivative, tax	(62)	(11)
Reclassification adjustment for derivative instruments, tax	$ 157	$ 143