Financial Statement Schedule II - Valuation and Qualifying Accounts (Detail) (Reserves and allowances deducted from asset accounts [Member], USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Reserves and allowances deducted from asset accounts [Member]
Valuation and Qualifying Accounts Disclosure [Line Items]
Balance at Beginning of Period	$ 16,916,455	$ 15,598,912	$ 16,589,779
Charged to Costs and Expenses	8,046,605	13,247,731	10,597,432
Deductions	(5,782,870)	(11,930,188)	(11,588,299)
Balance at end of period	$ 19,180,190	$ 16,916,455	$ 15,598,912