Summarized Financial Information for Reportable Segments (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended				6 Months Ended
	Jun. 30, 2013		Jun. 30, 2012		Jun. 30, 2013		Jun. 30, 2012		Dec. 31, 2012
Segment Reporting Disclosure [Line Items]
Revenues	$ 247,242		$ 149,332		$ 484,201		$ 304,006
Operating expenses	82,844		44,731		165,607		93,413
Depreciation and amortization expense	71,869		40,722		138,519		79,160
General and administrative expense	25,089		11,565		48,823		23,043
Other operating expense	1,892		240		1,983		195
Operating income (loss)	65,548		52,074		129,269		108,195
Income (loss) from unconsolidated affiliates	33,745		15,971		58,753		28,958
Total assets	7,216,570				7,216,570				6,561,100
Barnett
Segment Reporting Disclosure [Line Items]
Revenues	90,384		99,411		183,468		202,843
Operating expenses	23,963		23,735		47,902		49,935
Depreciation and amortization expense	24,000		23,283		47,915		45,854
General and administrative expense
Other operating expense
Operating income (loss)	42,421		52,393		87,651		107,054
Income (loss) from unconsolidated affiliates
Capital expenditures	13,395		20,316		34,399		58,994
Total assets	1,558,776		1,581,107		1,558,776		1,581,107
Eagle Ford
Segment Reporting Disclosure [Line Items]
Revenues	67,752				125,711
Operating expenses	14,951				29,351
Depreciation and amortization expense	13,362				23,449
General and administrative expense
Other operating expense
Operating income (loss)	39,439				72,911
Income (loss) from unconsolidated affiliates
Capital expenditures	83,443				165,359
Total assets	1,062,109				1,062,109
Haynesville
Segment Reporting Disclosure [Line Items]
Revenues	30,621		16,122		64,095		35,379
Operating expenses	9,109		3,564		20,424		7,711
Depreciation and amortization expense	19,471		7,924		38,757		15,710
General and administrative expense
Other operating expense
Operating income (loss)	2,041		4,634		4,914		11,958
Income (loss) from unconsolidated affiliates
Capital expenditures	2,777		5,279		10,562		11,856
Total assets	1,308,901		523,940		1,308,901		523,940
Marcellus
Segment Reporting Disclosure [Line Items]
Revenues	4,012				7,741
Operating expenses	198				2,795
Depreciation and amortization expense	38				161
General and administrative expense
Other operating expense
Operating income (loss)	3,776				4,785
Income (loss) from unconsolidated affiliates	34,492		15,971		59,738		28,958
Capital expenditures	5	[1]		[2]	189	[3]		[4]
Total assets	1,322,496		956,925		1,322,496		956,925
Niobrara
Segment Reporting Disclosure [Line Items]
Revenues	2,431				4,733
Operating expenses	1,946				3,490
Depreciation and amortization expense	1,156				1,875
General and administrative expense
Other operating expense
Operating income (loss)	(671)				(632)
Income (loss) from unconsolidated affiliates
Capital expenditures	11,671	[5]			23,197	[6]
Total assets	103,844				103,844
Utica
Segment Reporting Disclosure [Line Items]
Revenues	7,238				12,734
Operating expenses	2,269				4,815
Depreciation and amortization expense	2,265				3,465
General and administrative expense
Other operating expense
Operating income (loss)	2,704				4,454
Income (loss) from unconsolidated affiliates	(929)				(1,090)
Capital expenditures	94,023	[7]			165,359	[8]
Total assets	669,413				669,413
Mid-Continent
Segment Reporting Disclosure [Line Items]
Revenues	44,804		33,799		85,719		65,784
Operating expenses	16,975		12,245		35,179		24,608
Depreciation and amortization expense	8,208		7,972		16,806		15,469
General and administrative expense
Other operating expense
Operating income (loss)	19,621		13,582		33,734		25,707
Income (loss) from unconsolidated affiliates	182				105
Capital expenditures	29,134	[9]	32,029		68,130	[10]	54,696
Total assets	758,322		575,782		758,322		575,782
Corporate
Segment Reporting Disclosure [Line Items]
Operating expenses	13,433		5,187		21,651		11,159
Depreciation and amortization expense	3,369		1,543		6,091		2,127
General and administrative expense	25,089		11,565		48,823		23,043
Other operating expense	1,892		240		1,983		195
Operating income (loss)	(43,783)		(18,535)		(78,548)		(36,524)
Income (loss) from unconsolidated affiliates
Capital expenditures	40,192		2,704		83,979		15,375
Total assets	432,709		209,058		432,709		209,058
Consolidated
Segment Reporting Disclosure [Line Items]
Revenues	247,242		149,332		484,201		304,006
Operating expenses	82,844		44,731		165,607		93,413
Depreciation and amortization expense	71,869		40,722		138,519		79,160
General and administrative expense	25,089		11,565		48,823		23,043
Other operating expense	1,892		240		1,983		195
Operating income (loss)	65,548		52,074		129,269		108,195
Income (loss) from unconsolidated affiliates	33,745		15,971		58,753		28,958
Capital expenditures	274,640		60,328		545,594		140,921
Total assets	$ 7,216,570		$ 3,846,812		$ 7,216,570		$ 3,846,812

[1] Amount excludes $75.9 million for the Partnership’s share of capital expenditures included in investments in unconsolidated affiliates.

[2] Amount excludes $93.8 million for the Partnership’s share of capital expenditures included in investments in unconsolidated affiliates.

[3] Amount excludes $169.1 million for the Partnership’s share of capital expenditures included in investments in unconsolidated affiliates.

[4] Amount excludes $175.2 million for the Partnership’s share of capital expenditures included in investments in unconsolidated affiliates.

[5] Amount includes $5.8 million of capital expenditures attributable to noncontrolling interest owners.

[6] Amount includes $11.6 million of capital expenditures attributable to noncontrolling interest owners.

[7] Amount excludes $112.0 million for the Partnership’s share of capital expenditures included in investments in unconsolidated affiliates and includes $33.8 million of capital expenditures attributable to noncontrolling interest owners.

[8] Amount excludes $184.0 million for the Partnership’s share of capital expenditures included in investments in unconsolidated affiliates and includes $55.8 million of capital expenditures attributable to noncontrolling interest owners.

[9] Amount excludes $2.3 million for the Partnership’s share of capital expenditures included in investments in unconsolidated affiliates.

[10] Amount excludes $2.6 million for the Partnership’s share of capital expenditures included in investments in unconsolidated affiliates.