Basis of Presentation Revision of Financial Statements (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Revision of Financial Statements [Line Items]
Operating Expenses	$ 425.8	$ 615.8	$ 2,066.8	$ 1,182.0
As reported [Member]
Revision of Financial Statements [Line Items]
Revenue from Purchased Oil and Gas		215.0		382.3
Revenues		608.6		1,100.2
Cost of Purchased Oil and Gas		217.2		386.6
Operating Expenses		649.8		1,239.5
As revised [Member]
Revision of Financial Statements [Line Items]
Revenue from Purchased Oil and Gas		181.0		324.8
Revenues		574.6		1,042.7
Cost of Purchased Oil and Gas		183.2		329.1
Operating Expenses		615.8		1,182.0
Change [Member]
Revision of Financial Statements [Line Items]
Revenue from Purchased Oil and Gas		(34.0)		(57.5)
Revenues		(34.0)		(57.5)
Cost of Purchased Oil and Gas		(34.0)		(57.5)
Operating Expenses		$ (34.0)		$ (57.5)