Summarized Financial Information for Reportable Segments (Parenthetical) (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2014		Sep. 30, 2013		Sep. 30, 2014		Sep. 30, 2013
Segment Reporting Information [Line Items]
Capital expenditures	$ 246,706		$ 265,517		$ 767,876		$ 811,111
Marcellus
Segment Reporting Information [Line Items]
Capital expenditures	13,290	[1]	10	[2]	29,092	[3]	199	[4]
Marcellus | Investments In Unconsolidated Affiliates
Segment Reporting Information [Line Items]
Capital expenditures	42,700		75,400		113,600		244,500
Niobrara
Segment Reporting Information [Line Items]
Capital expenditures	73,495	[5]	20,839	[6]	162,013	[7]	44,036	[8]
Niobrara | Attributable to Noncontrolling Interest Owners
Segment Reporting Information [Line Items]
Capital expenditures	36,800		10,400		81,700		22,000
Utica
Segment Reporting Information [Line Items]
Capital expenditures	68,813	[9]	102,161	[10]	249,992	[11]	261,940	[12]
Utica | Investments In Unconsolidated Affiliates
Segment Reporting Information [Line Items]
Capital expenditures	41,000		103,500		192,900		287,500
Utica | Attributable to Noncontrolling Interest Owners
Segment Reporting Information [Line Items]
Capital expenditures	22,000		36,400		81,300		92,200
Mid-Continent
Segment Reporting Information [Line Items]
Capital expenditures	24,779	[13]	20,450	[14]	64,235	[13]	88,580	[15]
Mid-Continent | Investments In Unconsolidated Affiliates
Segment Reporting Information [Line Items]
Capital expenditures	$ 100		$ 1,300		$ 100		$ 3,900

[1] Amount excludes $42.7 million for the Partnership’s share of capital expenditures included in investments in unconsolidated affiliates.

[2] Amount excludes $75.4 million for the Partnership’s share of capital expenditures included in investments in unconsolidated affiliates.

[3] Amount excludes $113.6 million for the Partnership’s share of capital expenditures included in investments in unconsolidated affiliates.

[4] Amount excludes $244.5 million for the Partnership’s share of capital expenditures included in investments in unconsolidated affiliates.

[5] Amount includes $36.8 million of capital expenditures attributable to noncontrolling interest owners.

[6] Amount includes $10.4 million of capital expenditures attributable to noncontrolling interest owners.

[7] Amount includes $81.7 million of capital expenditures attributable to noncontrolling interest owners.

[8] Amount includes $22.0 million of capital expenditures attributable to noncontrolling interest owners.

[9] Amount excludes $41.0 million for the Partnership’s share of capital expenditures included in investments in unconsolidated affiliates and includes $22.0 million of capital expenditures attributable to noncontrolling interest owners.

[10] Amount excludes $103.5 million for the Partnership’s share of capital expenditures included in investments in unconsolidated affiliates and includes $36.4 million of capital expenditures attributable to noncontrolling interest owners.

[11] Amount excludes $192.9 million for the Partnership’s share of capital expenditures included in investments in unconsolidated affiliates and includes $81.3 million of capital expenditures attributable to noncontrolling interest owners.

[12] Amount excludes $287.5 million for the Partnership’s share of capital expenditures included in investments in unconsolidated affiliates and includes $92.2 million of capital expenditures attributable to noncontrolling interest owners.

[13] Amount excludes $0.1 million for the Partnership’s share of capital expenditures included in investments in unconsolidated affiliates.

[14] Amount excludes $1.3 million for the Partnership’s share of capital expenditures included in investments in unconsolidated affiliates.

[15] Amount excludes $3.9 million for the Partnership’s share of capital expenditures included in investments in unconsolidated affiliates