Summarized Financial Information for Reportable Segments (Parenthetical) (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Segment Reporting Information [Line Items]
Capital expenditures	$ 999,211		$ 1,058,599		$ 350,500
Niobrara | Attributable to Noncontrolling Interest Owners
Segment Reporting Information [Line Items]
Capital expenditures			29,600
Operating Segments | Marcellus Shale
Segment Reporting Information [Line Items]
Capital expenditures	42,791	[1]	2,590	[2]
Operating Segments | Marcellus Shale | Unconsolidated Affiliates
Segment Reporting Information [Line Items]
Capital expenditures	147,000		289,700		384,400
Operating Segments | Niobrara
Segment Reporting Information [Line Items]
Capital expenditures	213,749	[3]	59,115	[4]	1,967
Operating Segments | Niobrara | Noncontrolling Interest
Segment Reporting Information [Line Items]
Capital expenditures	107,600
Operating Segments | Utica
Segment Reporting Information [Line Items]
Capital expenditures	317,638	[5]	342,839	[6]	126
Operating Segments | Utica | Noncontrolling Interest
Segment Reporting Information [Line Items]
Capital expenditures	103,900		122,000
Operating Segments | Utica | Unconsolidated Affiliates
Segment Reporting Information [Line Items]
Capital expenditures	237,200		376,800
Operating Segments | Mid-Continent
Segment Reporting Information [Line Items]
Capital expenditures	100,889	[7]	106,718	[8]	184,285
Operating Segments | Mid-Continent | Unconsolidated Affiliates
Segment Reporting Information [Line Items]
Capital expenditures	$ 1,000		$ 4,900

[1] Amount excludes $147.0 million for the Partnership’s share of capital expenditures included in investments in unconsolidated affiliates.

[2] Amount excludes $289.7 million for the Partnership’s share of capital expenditures included in investments in unconsolidated affiliates

[3] Amount includes $107.6 million of capital expenditures attributable to noncontrolling interest owners.

[4] Amount includes $29.6 million of capital expenditures attributable to noncontrolling interest owners.

[5] Amount excludes $237.2 million for the Partnership’s share of capital expenditures included in investments in unconsolidated affiliates and includes $103.9 million of capital expenditures attributable to noncontrolling interest owners.

[6] Amount excludes $376.8 million for the Partnership’s share of capital expenditures included in investments in unconsolidated affiliates and includes $122.0 million of capital expenditures attributable to noncontrolling interest owners.

[7] Amount excludes $1.0 million for the Partnership’s share of capital expenditures included in investments in unconsolidated affiliates.

[8] Amount excludes $4.9 million for the Partnership’s share of capital expenditures included in investments in unconsolidated affiliates.