Consolidated Condensed Statements of Comprehensive Income (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Consolidated Condensed Statements of Comprehensive Income [Abstract]
Net income	$ 31,475	$ 22,196
Other comprehensive income (loss), net of tax
Change in pension plan assets and benefit obligations, net of income taxes of $222	412
Unrealized net holding gain (loss) on cash flow hedge, net of income taxes of $60 and $71	113	133
Unrealized net holding gain (loss) on securities available-for-sale, net of income tax benefit of $(1,188) and $(3,431)	(2,202)	(6,371)
Other comprehensive loss	(1,677)	(6,238)
Comprehensive income	$ 29,798	$ 15,958