Long-Term Debt (Long-Term Debt) (Detail) - USD ($) $ in Thousands		9 Months Ended	12 Months Ended
		Sep. 30, 2015	Dec. 31, 2014
Debt Instrument [Line Items]
Total debt		$ 1,958,716	$ 1,979,565
Less - current portion		(3,637)	(3,649)
Less - debt issuance costs		(8,225)	(4,764)
Long-term debt and notes payable		1,946,854	1,971,152
Term Loan Facility [Member]
Debt Instrument [Line Items]
Total debt			660,000
Revolver Under Prior Credit Agreement [Member]
Debt Instrument [Line Items]
Total debt			680,000
Senior Notes due 2015 [Member]
Debt Instrument [Line Items]
Total debt		$ 175,000	$ 175,000
Interest rate		6.22%	6.22%
Debt instrument maturity date year		2015	2015
Senior Notes due 2016 [Member]
Debt Instrument [Line Items]
Total debt		$ 100,000	$ 100,000
Interest rate		3.30%	3.30%
Debt instrument maturity date year		2016	2016
Senior Notes due 2018 [Member]
Debt Instrument [Line Items]
Total debt		$ 50,000	$ 50,000
Interest rate		4.00%	4.00%
Debt instrument maturity date year		2018	2018
Senior Notes due 2019 [Member]
Debt Instrument [Line Items]
Total debt		$ 175,000	$ 175,000
Interest rate		5.25%	5.25%
Debt instrument maturity date year		2019	2019
Senior Notes due 2021 [Member]
Debt Instrument [Line Items]
Total debt		$ 100,000	$ 100,000
Interest rate		4.64%	4.64%
Debt instrument maturity date year		2021	2021
Senior Notes due 2022 [Member]
Debt Instrument [Line Items]
Total debt		$ 125,000
Interest rate		3.09%
Debt instrument maturity date year		2022
Senior Notes due 2025 [Member]
Debt Instrument [Line Items]
Total debt		$ 375,000
Interest rate		3.41%
Debt instrument maturity date year		2025
Tax-exempt Bonds [Member]
Debt Instrument [Line Items]
Total debt	[1]	$ 31,430	$ 31,430
Interest rate, minimum	[1]	0.05%
Interest rate, maximum	[1]	0.19%
2.50% to 10.9% Notes Payable to Sellers and Other Third Parties [Member]
Debt Instrument [Line Items]
Total debt	[1]	$ 12,286	$ 8,135
Interest rate, minimum	[1]	2.50%
Interest rate, maximum	[1]	10.90%
Credit Agreement [Member] | Revolver Under Credit Facility [Member]
Debt Instrument [Line Items]
Total debt	[1]	$ 15,000
Interest rate, minimum	[1]	1.37%
Interest rate, maximum	[1]	3.45%
Credit Agreement [Member] | Term Loan Facility [Member]
Debt Instrument [Line Items]
Total debt	[1]	$ 800,000
Interest rate, minimum	[1]	1.37%
Interest rate, maximum	[1]	1.40%

[1] Interest rates in the table above represent the range of interest rates incurred during the nine month period ended September 30, 2015.