Summarized Financial Information for Reportable Segments (Parenthetical) (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
Marcellus
Segment Reporting Disclosure [Line Items]
Capital expenditures	$ 5	[1]		[2]	$ 189	[3]		[4]
Marcellus | Investments in Unconsolidated Affiliates
Segment Reporting Disclosure [Line Items]
Capital expenditures	75,900		93,800		169,100		175,200
Niobrara
Segment Reporting Disclosure [Line Items]
Capital expenditures	11,671	[5]			23,197	[6]
Niobrara | Attributable To Noncontrolling Interest Owners
Segment Reporting Disclosure [Line Items]
Capital expenditures	5,800				11,600
Utica
Segment Reporting Disclosure [Line Items]
Capital expenditures	94,023	[7]			165,359	[8]
Utica | Investments in Unconsolidated Affiliates
Segment Reporting Disclosure [Line Items]
Capital expenditures	112,000				184,000
Utica | Attributable To Noncontrolling Interest Owners
Segment Reporting Disclosure [Line Items]
Capital expenditures	33,800				55,800
Mid-Continent
Segment Reporting Disclosure [Line Items]
Capital expenditures	29,134	[9]	32,029		68,130	[10]	54,696
Mid-Continent | Investments in Unconsolidated Affiliates
Segment Reporting Disclosure [Line Items]
Capital expenditures	$ 2,300				$ 2,600

[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.