Summary of Significant Accounting Policies Revision of Financial Statements (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Purchased gas, oil and NGL sales	$ (620.8)	$ (913.9)	$ (774.9)
Purchased gas, oil and NGL expense	(626.8)	(910.1)	(783.5)
Operating Expenses	$ (2,400.8)	(3,991.9)	$ (2,585.6)
Purchased gas and oil sales as reported [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Purchased gas, oil and NGL sales		(1,035.0)
Revenues		(3,414.3)
Purchased gas, oil and NGL expense		(1,031.2)
Operating Expenses		(4,113.0)
Purchased gas and oil sales as revised [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Purchased gas, oil and NGL sales		(913.9)
Revenues		(3,293.2)
Purchased gas, oil and NGL expense		(910.1)
Operating Expenses		(3,991.9)
Change [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Purchased gas, oil and NGL sales		(121.1)
Revenues		(121.1)
Purchased gas, oil and NGL expense		(121.1)
Operating Expenses		$ (121.1)