Supplemental Cash Flow Information (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Supplemental Cash Flow Information [Abstract]
Interest paid	$ 123,140	$ 111,555
Income taxes paid	884	642
Assets acquired through capital leases and installment sales	7,782	7,061
Redeemable Convertible Preferred Stock [Member]
Supplemental Cash Flow Information [Abstract]
Conversion of redeemable convertible preferred stock (note 7)	$ 305,180	$ 0