Business Combinations (Details) (USD $)	12 Months Ended								12 Months Ended	0 Months Ended					12 Months Ended	0 Months Ended	12 Months Ended
	Dec. 31, 2013 item	Dec. 31, 2012 item	Dec. 31, 2011 item	Dec. 31, 2013 Southwest Segment	Dec. 31, 2013 Marcellus	Dec. 31, 2013 Northeast Segment	Dec. 31, 2013 Buffalo Creek Acquisition	May 08, 2013 Buffalo Creek Acquisition	Dec. 31, 2013 Buffalo Creek Acquisition Southwest Segment	May 08, 2013 Buffalo Creek Acquisition Chesapeake mi acre	May 08, 2013 Buffalo Creek Acquisition Chesapeake Texas mi	May 08, 2013 Buffalo Creek Acquisition Chesapeake Oklahoma mi	May 29, 2012 Keystone Acquisition item sqmi	Dec. 31, 2013 Keystone Acquisition	Dec. 31, 2013 Keystone Acquisition Marcellus	Feb. 02, 2011 Langley Acquisition	Dec. 31, 2012 Langley Acquisition	Dec. 31, 2013 Langley Acquisition Northeast Segment
Business Combination
Cash purchase price										$ 225,200,000			$ 507,300,000			$ 230,700,000
Cash paid prior to giving effect to the final working capital adjustment													509,600,000
Receivables for working capital adjustment														2,300,000
Number of cryogenic natural gas processing plants acquired													2
Capacity of cryogenic gas processing plant (in MMcf/d)										200			90			100
Capacity of refrigeration natural gas processing plant (in MMcf/d)																75
Additional capacity of cryogenic natural gas processing plant installed (in MMcf/d)																	150
Length of gas gathering pipeline (in miles)											22	5
Length of rights-of-way associated with the future construction of a high-pressure trunk line (in miles)										30
Area of land (in acres/square miles)										130,000			900
Extended additional term of the keep-whole processing agreement										5 years
Additional cash paid as consideration for extension term of the keep-whole processing agreement										20,000,000
Useful life of intangible assets acquired									20 years						19 years			12 years
Assets:
Cash													2,837,000
Accounts receivable													1,756,000
Inventory													86,000			1,806,000
Property, plant and equipment								144,115,000					136,593,000			136,525,000
Goodwill	144,856,000	142,174,000		8,155,000	74,256,000	62,445,000		2,682,000					74,256,000			58,497,000
Intangible asset								84,500,000					304,708,000			33,900,000
Liabilities:
Accounts payable								(6,087,000)					(12,117,000)
Other short-term liabilities													(175,000)
Other long-term liabilities													(632,000)
Total							$ 225,200,000	$ 225,210,000					$ 507,312,000			$ 230,728,000
Number of acquisitions made	1	1	1