Rates and Other Regulatory Activities - Additional Information (Detail) (White Oak Lateral Mainline Expansion [Member], Eastern Shore [Member], USD $)	12 Months Ended
	Dec. 31, 2014 in mi
White Oak Lateral Mainline Expansion [Member] | Eastern Shore [Member]
Rates and Other Regulatory Activities [Line Items]
Volume The Expansion Project Is Expected to Provide	45,000
Number of Pipeline Miles	7.2
Lateral diamater of pipeline to be installed	16
Horsepower Of Additional Compression	3,550
Estimated capital cost	$ 29.8000