Business Acquisitions (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended		12 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2012
As reported [Abstract]
Revenues	$ 1,397.8	$ 1,645.8	$ 5,885.7
Net income	33.8	69.2	159.3
Less: Net income attributable to noncontrolling interests	20.4	59.6	121.2
Net income attributable to Targa Resources Corp.	13.4	9.6	38.1
Net income per common share - Basic (in dollars per share)	$ 0.32	$ 0.23	$ 0.93
Net income per common share - Diluted (in dollars per share)	$ 0.32	$ 0.23	$ 0.91
Pro Forma Results [Abstract]
Revenues		1,648.7	5,909.9
Net income		59.2	129.5
Less: Net income attributable to noncontrolling interests		47.3	83.5
Net income attributable to Targa Resources Corp.		11.9	46.0
Net income per common share - Basic		$ 0.29	$ 1.12
Net income per common share - Diluted		$ 0.28	$ 1.10
Useful life of acquired property, plant and equipment - minimum	15 years
Useful life of acquired property, plant and equipment - maximum	20 years
Useful life of acquired definite-lived intangibles	20 years
Useful life of acquired property, plant, and equipment - pro-forma as reported in 10-K	30 years
Useful life of acquired definite-lived intangibles - pro-forma as reported in 10-K	30 years
Badlands [Member]
Business Acquisition [Line Items]
Contingent consideration			50
Fair value of contingent consideration	15.6		15.3
Increase in contingent consideration attributable to accretion of the discount factor	$ 0.3