Segment Reporting (Summary of Financial Information Concerning Company's Reportable Segments) (Detail) - USD ($) $ in Thousands		3 Months Ended										12 Months Ended
		Dec. 31, 2016		Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015		Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016		Dec. 31, 2015		Dec. 31, 2014
Segment Reporting Information [Line Items]
Revenue		$ 1,048,622		$ 1,084,922	$ 727,639	$ 514,680	$ 531,937		$ 547,938	$ 531,312	$ 506,100	$ 3,375,863		$ 2,117,287		$ 2,079,166
Segment EBITDA	[1]											943,888		702,394		711,304
Depreciation and amortization												463,912		269,434		257,944
Capital expenditures												344,723		238,833		241,277
Total assets	[2]	11,193,102					5,121,798					11,193,102		5,121,798		5,245,267
Intercompany Revenues [Member]
Segment Reporting Information [Line Items]
Revenue	[3]											(470,465)		(273,903)		(259,352)
Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenue												3,846,328		2,391,190		2,338,518
Segment EBITDA												1,063,103		700,461		718,738
Southern [Member]
Segment Reporting Information [Line Items]
Revenue												713,381		145,289		135,530
Segment EBITDA	[1]											163,320		35,718		32,539
Depreciation and amortization												99,323		19,959		17,487
Capital expenditures												64,624		20,779		32,033
Total assets	[2]	2,869,841					259,046					2,869,841		259,046		249,437
Southern [Member] | Intercompany Revenues [Member]
Segment Reporting Information [Line Items]
Revenue	[3]											(96,545)		(23,566)		(22,950)
Southern [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenue												809,926		168,855		158,480
Segment EBITDA												163,320		35,718		32,539
Western [Member]
Segment Reporting Information [Line Items]
Revenue												935,319		880,393		823,922
Segment EBITDA	[1]											315,708		290,937		258,126
Depreciation and amortization												89,198		83,073		79,907
Capital expenditures												86,200		82,118		65,227
Total assets	[2]	1,516,870					1,498,296					1,516,870		1,498,296		1,482,474
Western [Member] | Intercompany Revenues [Member]
Segment Reporting Information [Line Items]
Revenue	[3]											(116,318)		(103,890)		(96,194)
Western [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenue												1,051,637		984,283		920,116
Segment EBITDA												315,708		290,937		258,126
Eastern [Member]
Segment Reporting Information [Line Items]
Revenue												636,652		376,156		342,338
Segment EBITDA	[1]											193,361		119,668		104,224
Depreciation and amortization												91,336		52,132		47,269
Capital expenditures												82,434		44,299		50,252
Total assets	[2]	1,541,854					1,062,761					1,541,854		1,062,761		740,015
Eastern [Member] | Intercompany Revenues [Member]
Segment Reporting Information [Line Items]
Revenue	[3]											(114,758)		(75,313)		(68,768)
Eastern [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenue												751,410		451,469		411,106
Segment EBITDA												193,361		119,668		104,224
Canada [Member]
Segment Reporting Information [Line Items]
Revenue												407,861
Segment EBITDA	[1]											149,305
Depreciation and amortization												68,640
Capital expenditures												20,424
Total assets	[2]	2,532,046										2,532,046
Canada [Member] | Intercompany Revenues [Member]
Segment Reporting Information [Line Items]
Revenue	[3]											(58,597)
Canada [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenue												466,458
Segment EBITDA												149,305
Central [Member]
Segment Reporting Information [Line Items]
Revenue												561,541	[4],[5]	500,211		475,877	[4],[5]
Segment EBITDA	[1]											208,930	[4],[5]	184,006		175,935	[4],[5]
Depreciation and amortization												70,027	[4],[5]	64,072		57,902	[4],[5]
Capital expenditures												71,888	[4],[5]	57,163		55,481	[4],[5]
Total assets	[2]	1,302,900	[4],[5]				1,070,505					1,302,900	[4],[5]	1,070,505		1,050,436	[4],[5]
Central [Member] | Intercompany Revenues [Member]
Segment Reporting Information [Line Items]
Revenue	[3]											(72,852)	[4],[5]	(59,590)		(56,538)	[4],[5]
Central [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenue												634,393	[4],[5]	559,801		532,415	[4],[5]
Segment EBITDA												208,930		184,006		175,935
Exploration and Production [Member]
Segment Reporting Information [Line Items]
Revenue												121,109		215,238	[4],[5]	301,499
Segment EBITDA	[1]											32,479		70,132	[4],[5]	147,914
Depreciation and amortization												41,215		47,339	[4],[5]	52,805
Capital expenditures												10,178		31,632	[4],[5]	36,726
Total assets	[2]	1,068,086					1,115,234	[4],[5]				1,068,086		1,115,234	[4],[5]	1,610,133
Exploration and Production [Member] | Intercompany Revenues [Member]
Segment Reporting Information [Line Items]
Revenue	[3]											(11,395)		(11,544)	[4],[5]	(14,902)
Exploration and Production [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Revenue												132,504		226,782	[4],[5]	316,401
Segment EBITDA												32,479		70,132		147,914
Corporate [Member]
Segment Reporting Information [Line Items]
Segment EBITDA	[1],[4],[5]											(119,215)		1,933		(7,434)
Depreciation and amortization	[4],[5]											4,173		2,859		2,574
Capital expenditures	[4],[5]											8,975		2,842		1,558
Total assets	[2],[4],[5]	$ 361,505					$ 115,956					$ 361,505		$ 115,956		$ 112,772

[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] Goodwill is included within total assets for each of the Company's six 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.

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

[5] 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 six operating segments.