Business Segments (Details) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2016 USD ($)	Sep. 30, 2015 USD ($)	Sep. 30, 2016 USD ($) Segment	Sep. 30, 2015 USD ($)
Business Segments [Abstract]
Number of reportable segments | Segment			5
Segment Gross Operating Margin [Abstract]
Revenues	$ 5,920.4	$ 6,307.9	$ 16,543.5	$ 20,872.9
Subtract operating costs and expenses	(5,065.7)	(5,452.6)	(14,034.8)	(18,426.5)
Add equity in income of unconsolidated affiliates	92.3	103.1	269.8	302.5
Add depreciation, amortization and accretion expense amounts not reflected in gross operating margin	367.1	351.1	1,085.6	1,082.0
Add asset impairment charges not reflected in gross operating margin	6.8	26.8	21.6	139.1
Add net losses or subtract net gains attributable to asset sales, insurance recoveries and related property damage not reflected in gross operating margin	(8.9)	12.3	4.8	14.7
Add non-refundable payments attributable to shipper make-up rights on new pipeline projects reflected in gross operating margin	1.2	3.4	10.1	39.3
Subtract subsequent revenue recognition of deferred revenues attributable to make-up rights not reflected in gross operating margin	(5.6)	(10.9)	(25.1)	(45.3)
Total segment gross operating margin	1,307.6	1,341.1	3,875.5	3,978.7
Reconciliation of total Segment Gross Operating Margin [Abstract]
Total segment gross operating margin	1,307.6	1,341.1	3,875.5	3,978.7
Adjustments to reconcile total segment gross operating margin to operating income:
Subtract depreciation, amortization and accretion expense amounts not reflected in gross operating margin	(367.1)	(351.1)	(1,085.6)	(1,082.0)
Subtract asset impairment charges not reflected in gross operating margin	(6.8)	(26.8)	(21.6)	(139.1)
Add net gains or subtract net losses attributable to asset sales, insurance recoveries and related property damage not reflected in gross operating margin	8.9	(12.3)	(4.8)	(14.7)
Subtract non-refundable payments attributable to shipper make-up rights on new pipeline projects reflected in gross operating margin	(1.2)	(3.4)	(10.1)	(39.3)
Add subsequent revenue recognition of deferred revenues attributable to make-up rights not reflected in gross operating margin	5.6	10.9	25.1	45.3
Subtract general and administrative costs not reflected in gross operating margin	(42.0)	(49.0)	(121.0)	(143.2)
Operating income	905.0	909.4	2,657.5	2,605.7
Other expense, net	(257.1)	(246.2)	(761.1)	(736.4)
Income before income taxes	$ 647.9	$ 663.2	$ 1,896.4	$ 1,869.3