Supplemental Cash Flow Information (Tables)

9 Months Ended

Sep. 30, 2012

Supplemental Cash Flow Information [Abstract]

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

	Nine Months Ended September 30,
	2012		2011
Supplemental disclosure of cash flow information:
Interest paid	$	364,507	$	312,992
Income taxes paid	3,092		4,343
Supplemental disclosure of non-cash financing activities:
Assets acquired through capital leases and installment sales	21,139		20,213
Conversion of redeemable convertible preferred stock (note 7)	305,180		—