Segment Reporting (Reconciliation of Primary Measure of Segment Profitability to Income before Income Tax Provision) (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended	12 Months Ended
	Sep. 30, 2012	Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2011
EBITDA		$ 651,339	[1]	$ 507,807	[1]	$ 485,819	[1]
Depreciation		(218,454)		(169,027)		(147,036)
Amortization of intangibles		(25,410)		(24,557)		(20,064)
Loss on disposal of assets		(2,853)		(1,627)		(1,657)
Gain from litigation settlement	3,551			3,551
Loss on prior office leases		(9,902)
Interest expense		(73,579)		(53,037)		(44,520)
Other income (expense), net		(220)		1,993		587
Income before income tax provision		320,921		265,103		273,129
Western [Member]
EBITDA		249,548	[1]	229,427	[1]	232,940	[1]
Central [Member]
EBITDA		182,790	[1]	164,756	[1]	145,088	[1]
Eastern [Member]
EBITDA		108,173	[1]	101,046	[1]	95,301	[1]
Exploration and Production [Member]
EBITDA		111,056	[1]	23,651	[1]	6,971	[1],[2],[3]
Corporate [Member]
EBITDA		(228)	[1],[2],[3]	(11,073)	[1],[2],[3]	5,519	[1]
Operating Segments [Member]
EBITDA		651,567		518,880		480,300
Operating Segments [Member] | Western [Member]
EBITDA		249,548		229,427		232,940
Operating Segments [Member] | Central [Member]
EBITDA		182,790		164,756		145,088
Operating Segments [Member] | Eastern [Member]
EBITDA		108,173		101,046		95,301
Operating Segments [Member] | Exploration and Production [Member]
EBITDA		$ 111,056		$ 23,651		$ 6,971

[1] For those items included in the determination of EBITDA, the accounting policies of the segments are the same as those described in Note 1.

[2] Corporate functions include accounting, legal, tax, treasury, information technology, risk management, human resources, training and other administrative functions.  Amounts reflected are net of allocations to the four operating segments.

[3] Corporate assets include cash, net deferred tax assets, debt issuance costs, equity investments, and corporate facility leasehold improvements and equipment.