Segment Information - Summary of Consolidated Revenues by Product and Service (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Revenue from External Customer [Line Items]
Sales of commodities									$ 5,626.8	$ 5,465.4	$ 7,595.2
Fees from midstream services									1,064.1	1,193.2	1,021.3
Total revenues	$ 2,012.6	$ 1,652.3	$ 1,583.6	$ 1,442.4	$ 1,647.4	$ 1,632.1	$ 1,699.4	$ 1,679.7	6,690.9	6,658.6	8,616.5
Natural Gas Sales [Member]
Revenue from External Customer [Line Items]
Sales of commodities									1,584.5	1,578.6	1,414.1
NGL Sales [Member]
Revenue from External Customer [Line Items]
Sales of commodities									3,777.3	3,558.3	5,960.1
Condensate Sales [Member]
Revenue from External Customer [Line Items]
Sales of commodities									133.9	142.4	134.3
Petroleum Products [Member]
Revenue from External Customer [Line Items]
Sales of commodities									68.2	101.6	96.3
Derivative Activities [Member]
Revenue from External Customer [Line Items]
Sales of commodities									62.9	84.5	(9.6)
Fractionating and Treating Fees [Member]
Revenue from External Customer [Line Items]
Fees from midstream services									126.2	209.0	208.9
Storage, Terminaling, Transportation and Export Fees [Member]
Revenue from External Customer [Line Items]
Fees from midstream services									420.0	506.2	548.1
Gathering and Processing Fees [Member]
Revenue from External Customer [Line Items]
Fees from midstream services									445.0	393.7	196.9
Other [Member]
Revenue from External Customer [Line Items]
Fees from midstream services									$ 72.9	$ 84.3	$ 67.4