Acquisitions and Divestitures - Additional Information (Detail) (Chesapeake Midstream Operating, L.L.C., USD $)	1 Months Ended	9 Months Ended
	Dec. 20, 2012	Sep. 30, 2013
Business Acquisition [Line Items]
Business acquisition, effective date of acquisition	Dec. 20, 2012
Percentage of equity interest acquired	100.00%
Consideration paid for acquisition	$ 2,160,000,000	$ 2,160,000,000
Proceeds from Divestiture of Businesses		32,900,000
Property, Plant and Equipment
Business Combination, Separately Recognized Transactions [Abstract]
Decrease to property, plant and equipment		70,800,000
Finite-Lived Intangible Assets
Business Combination, Separately Recognized Transactions [Abstract]
Decrease to property, plant and equipment		55,400,000
Other Assets
Business Combination, Separately Recognized Transactions [Abstract]
Decrease to property, plant and equipment		$ 15,400,000