Long-Term Debt (Parenthetical) (Detail)	3 Months Ended
	Mar. 31, 2013
Revolver Under Credit Facility
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage Rate Range, Minimum	1.47%	[1]
Debt Instrument, Interest Rate, Stated Percentage Rate Range, Maximum	4.25%	[1]
Term Loan Facility
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage Rate Range, Minimum	2.20%	[1]
Debt Instrument, Interest Rate, Stated Percentage Rate Range, Maximum	2.70%	[1]
6.22% Senior Notes due 2015
Debt Instrument [Line Items]
Interest Rate	6.22%
Maturity year	2015
3.30% Senior Notes due 2016
Debt Instrument [Line Items]
Interest Rate	3.30%
Maturity year	2016
4.00% Senior Notes due 2018
Debt Instrument [Line Items]
Interest Rate	4.00%
Maturity year	2018
5.25% Senior Notes due 2019
Debt Instrument [Line Items]
Interest Rate	5.25%
Maturity year	2019
4.64% Senior Notes due 2021
Debt Instrument [Line Items]
Interest Rate	4.64%
Maturity year	2021
Tax-exempt bonds
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage Rate Range, Minimum	0.12%	[1]
Debt Instrument, Interest Rate, Stated Percentage Rate Range, Maximum	0.24%	[1]
2.5% to 10.9% notes payable to sellers and other third parties
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage Rate Range, Minimum	2.50%	[1]
Debt Instrument, Interest Rate, Stated Percentage Rate Range, Maximum	10.90%	[1]

[1] Interest rates in the table above represent the range of interest rates incurred during the three month period ended March 31, 2013.