Condensed Consolidated Statements Of Comprehensive Income (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Condensed Consolidated Statements Of Comprehensive Income [Abstract]
Net Income	$ 61,071	$ 85,386
Other comprehensive income, net of tax:
Prior service cost amortization, net of income tax of $151 and $135	(237)	(211)
Net actuarial pension loss amortization, net of income tax of $272 and $186	423	290
Unrealized (losses) on available-for-sale securities, net of income tax of $0 and $0	(23)	(133)
Other comprehensive income (loss), net of tax	163	(54)
Comprehensive income	$ 61,234	$ 85,332