Segment Reporting (Reconciliation of Primary Measure of Segment Profitability to Income before Income Tax Provision) (Detail) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Segment EBITDA	[1]	$ 702,394	$ 711,304	$ 651,339
Depreciation		(240,357)	(230,944)	(218,454)
Amortization of intangibles		(29,077)	(27,000)	(25,410)
Loss on prior office leases				(9,902)
Impairments and other operating charges		(494,492)	(4,091)	(4,129)
Interest expense		(64,236)	(64,674)	(73,579)
Other income (expense), net		(518)	1,067	1,056
Income (loss) before income tax provision		(126,286)	385,662	320,921
Western [Member]
Segment EBITDA	[1]	290,937	258,126	249,548
Central [Member]
Segment EBITDA	[1]	207,205	197,121	182,790
Eastern [Member]
Segment EBITDA	[1]	132,774	116,230	108,173
Exploration and Production [Member]
Segment EBITDA	[1]	69,545	147,261	111,056	[2],[3]
Loss on prior office leases				(742)
Corporate [Member]
Segment EBITDA	[1],[2],[3]	1,933	(7,434)	(228)
Loss on prior office leases				(9,160)
Operating Segments [Member]
Segment EBITDA		700,461	718,738	651,567
Operating Segments [Member] | Western [Member]
Segment EBITDA		290,937	258,126	249,548
Operating Segments [Member] | Central [Member]
Segment EBITDA		207,205	197,121	182,790
Operating Segments [Member] | Eastern [Member]
Segment EBITDA		132,774	116,230	108,173
Operating Segments [Member] | Exploration and Production [Member]
Segment EBITDA		$ 69,545	$ 147,261	$ 111,056

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

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

[3] 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.