Long-Term Debt (Narrative) (Details) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended	12 Months Ended
	Mar. 31, 2015	Dec. 31, 2014	Feb. 20, 2014	Mar. 07, 2014	Feb. 05, 2015
Debt Instrument [Line Items]
Other Long-term Debt	$ 0.3	0.4
Long-term Debt	2,493.7	2,022.5
Line of Credit Facility, Maximum Borrowing Capacity	1,500.0		1,000.0
Line Of Credit Facility, Additional Borrowing Limit	500.0
Line of Credit Facility, Interest Rate During Period	0.50%
Letters of Credit Outstanding, Amount	2.9
Line of Credit Facility, Amount Outstanding	709.0
Line of Credit Facility, Remaining Borrowing Capacity	788.1
Percentage Rate	1.00%
Enlink Midstream, Inc.
Debt Instrument [Line Items]
Limited Liability Company (LLC) or Limited Partnership (LP), Members or Limited Partners, Ownership Interest	6.00%
EnLink Midstream Partners GP, LLC [Member]
Debt Instrument [Line Items]
Limited Liability Company (LLC) or Limited Partnership (LP), Members or Limited Partners, Ownership Interest	100.00%
Maximum [Member]
Debt Instrument [Line Items]
Leverage ratios	5.0
Conditional acquisition purchase price	50.0
Minimum [Member]
Debt Instrument [Line Items]
Interest Coverge Ratio	2.50
Revolving Credit Facility [Member] | Maximum [Member]
Debt Instrument [Line Items]
Leverage ratios	5.5
Base Rate [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Interest Rate During Period	0.50%
Eurodollar [Member] | Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Interest Rate During Period	1.00%
ENLC Credit Facility [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	250.0			250.0
Line of Credit Facility, Amount Outstanding	0	0
Line of Credit Facility, Remaining Borrowing Capacity	250.0
ENLC Credit Facility [Member] | Enlink Midstream, Inc.
Debt Instrument [Line Items]
Limited Liability Company (LLC) or Limited Partnership (LP), Managing Member or General Partner, Ownership Interest, Shares	17,431,152
ENLC Credit Facility [Member] | Maximum [Member]
Debt Instrument [Line Items]
Leverage ratios	4.00
ENLC Credit Facility [Member] | AcquisitionPeriod [Member] | Maximum [Member]
Debt Instrument [Line Items]
Leverage ratios	4.50
Letter of Credit [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	500.0			125.0
7.125% Senior Notes due 2022
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	7.125%	7.125%
Senior Notes	183.7	184.4
Debt Instrument, Unamortized Discount (Premium), Net	21.1	21.9
2.7% Senior Notes due 2019
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	2.70%	2.70%
Senior Notes	399.5	399.5
Debt Instrument, Unamortized Discount (Premium), Net	(0.5)	(0.5)
4.4% Senior Notes due 2024
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	4.40%	4.40%
Senior Notes	553.1	553.2
Debt Instrument, Unamortized Discount (Premium), Net	3.1	3.2
5.6% Senior Notes due 2044
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	5.60%	5.60%
Senior Notes	349.7	349.7
Debt Instrument, Unamortized Discount (Premium), Net	(0.3)	(0.3)
5.05% Senior Notes due 2045
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	5.05%	5.05%
Senior Notes	298.4	298.3
Debt Instrument, Unamortized Discount (Premium), Net	(1.6)	(1.7)
Line of Credit [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Interest Rate During Period	1.60%	1.90%
Post Amendment [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity					$ 1,500.0