Other (Details) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Property, Plant and Equipment [Line Items]
Total property, plant and equipment, net	$ 5,777,392,000	$ 5,551,913,000
Other expense, net	(32,606,000)	(21,230,000)	(12,988,000)
Operation and maintenance	264,631,000	299,734,000	281,496,000
Regulatory assets	294,100,000	251,600,000
Rockaway Delivery Lateral Project [Member]
Property, Plant and Equipment [Line Items]
Total property, plant and equipment, net		8,700,000
Other expense, net		8,700,000
Northeast Connector Project [Member]
Property, Plant and Equipment [Line Items]
Total property, plant and equipment, net		2,400,000
Other expense, net		2,400,000
Northeast Supply Link Expansion Project [Member]
Property, Plant and Equipment [Line Items]
Total property, plant and equipment, net			10,100,000
Other expense, net			10,100,000
Eminence Storage Field [Member]
Property, Plant and Equipment [Line Items]
Total property, plant and equipment, net	(92,000,000)
Other expense, net	(11,500,000)
Operation and maintenance	4,300,000	2,500,000	14,600,000
Regulatory assets	92,000,000
Insurance recoveries	$ 16,100,000