Statement of Stockholders' Equity (Parenthetical) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Statement Of Stockholders Equity [Abstract]
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Tax	$ 2,007	$ 1,293	$ 7,214
Other Comprehensive Income (Loss), Available-for-sale Securities, Tax	2,948	790	(283)
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Net Unamortized Gain (Loss) Arising During Period, Tax	(173,699)	(28,710)	(5,116)
Other Comprehensive Income (Loss), Reclassification, Pension and Other Postretirement Benefit Plans, Net Gain (Loss) Recognized in Net Periodic Benefit Cost, Tax	$ 34,474	$ 28,298	$ 17,328