Summary of Financial Information Concerning Company's Reportable Segments (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2013		Sep. 30, 2012		Sep. 30, 2013		Sep. 30, 2012
Segment Reporting Information [Line Items]
Revenues	$ 503,646		$ 425,654		$ 1,442,918		$ 1,212,815
EBITDA	175,969	[1]	134,434	[1]	488,640	[1]	370,565	[1]
Western
Segment Reporting Information [Line Items]
Revenues	210,211		203,963		606,195		586,166
Central
Segment Reporting Information [Line Items]
Revenues	134,333		125,795		379,360		342,305
Eastern
Segment Reporting Information [Line Items]
Revenues	96,060		92,758		279,554		275,431
Exploration and Production
Segment Reporting Information [Line Items]
Revenues	63,042		3,138		177,809		8,913
Corporate, Non-Segment
Segment Reporting Information [Line Items]
EBITDA	188	[1],[2]	(1,992)	[1],[2]	(2,679)	[1],[2]	(9,823)	[1],[2]
Operating Segments
Segment Reporting Information [Line Items]
Revenues	569,350		484,599		1,632,229		1,386,995
EBITDA	175,781		136,426		491,319		380,388
Operating Segments | Western
Segment Reporting Information [Line Items]
Revenues	236,849		228,906		682,705		660,679
EBITDA	67,773	[1]	61,119	[1]	188,736	[1]	173,810	[1]
Operating Segments | Central
Segment Reporting Information [Line Items]
Revenues	151,181		139,802		426,353		384,520
EBITDA	48,845	[1]	47,072	[1]	137,600	[1]	122,688	[1]
Operating Segments | Eastern
Segment Reporting Information [Line Items]
Revenues	115,944		112,753		336,916		332,883
EBITDA	28,038	[1]	26,113	[1]	82,947	[1]	77,879	[1]
Operating Segments | Exploration and Production
Segment Reporting Information [Line Items]
Revenues	65,376		3,138		186,255		8,913
EBITDA	31,125	[1]	2,122	[1]	82,036	[1]	6,011	[1]
Intersegment Eliminations
Segment Reporting Information [Line Items]
Revenues	(65,704)	[3]	(58,945)	[3]	(189,311)	[3]	(174,180)	[3]
Intersegment Eliminations | Western
Segment Reporting Information [Line Items]
Revenues	(26,638)	[3]	(24,943)	[3]	(76,510)	[3]	(74,513)	[3]
Intersegment Eliminations | Central
Segment Reporting Information [Line Items]
Revenues	(16,848)	[3]	(14,007)	[3]	(46,993)	[3]	(42,215)	[3]
Intersegment Eliminations | Eastern
Segment Reporting Information [Line Items]
Revenues	(19,884)	[3]	(19,995)	[3]	(57,362)	[3]	(57,452)	[3]
Intersegment Eliminations | Exploration and Production
Segment Reporting Information [Line Items]
Revenues	$ (2,334)	[3]			$ (8,446)	[3]

[1] For those items included in the determination of EBITDA, the accounting policies of the segments are the same as those described in the Company's most recent Annual Report on Form 10-K.

[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] Intercompany revenues reflect each segment's total intercompany sales, including intercompany sales within a segment and between segments. Transactions within and between segments are generally made on a basis intended to reflect the market value of the service.