Business Segments, Gross Operating Margin (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Segment Gross Operating Margin [Abstract]
Revenues	$ 6,155.0	$ 6,307.9	$ 7,092.5	$ 7,472.5	$ 10,190.3	$ 12,330.2	$ 12,520.8	$ 12,909.9	$ 27,027.9	$ 47,951.2	$ 47,727.0
Subtract operating costs and expenses									(23,668.7)	(44,220.5)	(44,238.7)
Add equity in income of unconsolidated affiliates									373.6	259.5	167.3
Add depreciation, amortization and accretion expense amounts not reflected in gross operating margin									1,428.2	1,282.7	1,148.9
Add impairment charges not reflected in gross operating margin									162.6	34.0	92.6
Add net losses or subtract net gains attributable to asset sales and insurance recoveries not reflected in gross operating margin									15.6	(102.1)	(83.4)
Add non-refundable deferred revenues attributable to shipper make-up rights on major new pipeline projects reflected in gross operating margin									53.6	84.6	4.4
Subtract subsequent recognition of deferred revenues attributable to make-up rights not reflected in gross operating margin									(60.7)	(2.9)	0.0
Total segment gross operating margin									5,332.1	5,286.5	4,818.1
Reconciliation of Total Segment Gross Operating Margin [Abstract]
Total segment gross operating margin									5,332.1	5,286.5	4,818.1
Adjustments to reconcile total segment gross operating margin to operating income:
Subtract depreciation, amortization and accretion expense amounts not reflected in gross operating margin									(1,428.2)	(1,282.7)	(1,148.9)
Subtract impairment charges not reflected in gross operating margin									(162.6)	(34.0)	(92.6)
Add net gains or subtract net losses attributable to asset sales and insurance recoveries not reflected in gross operating margin									(15.6)	102.1	83.4
Subtract non-refundable deferred revenues attributable to shipper make-up rights on major new pipeline projects reflected in gross operating margin									(53.6)	(84.6)	(4.4)
Add subsequent recognition of deferred revenues attributable to make-up rights not reflected in gross operating margin									60.7	2.9	0.0
Subtract general and administrative costs not reflected in gross operating margin									(192.6)	(214.5)	(188.3)
Operating income	$ 934.5	$ 909.4	$ 800.3	$ 896.0	$ 921.0	$ 937.7	$ 884.3	$ 1,032.7	3,540.2	3,775.7	3,467.3
Other expense, net									(984.3)	(919.1)	(802.7)
Income before income taxes									$ 2,555.9	$ 2,856.6	$ 2,664.6