Supplemental Cash Flow Information (Tables)

3 Months Ended

Mar. 31, 2012

Supplemental Cash Flow Information [Abstract]

Supplemental Disclosure of Cash Flow Information and Non-cash Investing and Financing Activities

	Three Months Ended March 31,
	2012		2011
Supplemental disclosure of cash flow information:
Interest paid	$	123,140	$	111,555
Income taxes paid	884		642
Supplemental disclosure of non-cash financing activities:
Assets acquired through capital leases and installment sales	7,782		7,061
Conversion of redeemable convertible preferred stock (note 7)	305,180		—