Accumulated Other Comprehensive Income (Loss) (Details 2) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Reclassifications out of accumulated other comprehensive income (loss):
Interest expense	$ 18,722	$ 11,594
Income tax benefit	(36,399)	(3,756)
Net of tax in 2013	62,113	115,043
Total reclassifications	83	166
Amortization of loss on interest rate hedge | Amount Reclassified from Accumulated Other Comprehensive Income
Reclassifications out of accumulated other comprehensive income (loss):
Interest expense	(65)
Income tax benefit	26
Net of tax in 2013	(39)
Amortization of deferred actuarial loss and prior service cost | Amount Reclassified from Accumulated Other Comprehensive Income
Reclassifications out of accumulated other comprehensive income (loss):
Operating expenses	202	166
Income tax benefit	(80)
Net of tax in 2013	$ 122	$ 166