Partnership Units and Related Matters (Details) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Dec. 31, 2012
Partnership Equity [Abstract]
General partner ownership interest (in hundredths)	2.00%
Aggregate amount of debt or equity securities allowed to be issued under the shelf agreement	$ 300
Number of days from end of each quarter by when cash is distributed to unitholders	45 days
Date paid or to be paid	May 15, 2013	Feb. 14, 2013
Distributions Paid Limited Partners Common	71.7	69.0
Distributions to General Partners (Incentive)	22.1	20.1
Distributions to General Partners (2%)	1.9	1.8
Total distributions to general and limited partners	95.7	90.9
Distributions to Targa Resources Corp.	33.0	30.7
Distributions per limited partner per unit (in dollars per unit)	$ 0.6975	$ 0.6800
2012 EDA [Member]
Partnership Equity [Abstract]
Number of common units sold (in shares)	2,420,046
Gross proceeds from sale of common units	96.7
Dollar amount of Common Units able to sell from Equity Distribution Agreement	100
General partner contributed to maintain general partner ownership percentage	2.0
General partner ownership interest (in hundredths)	2.00%
2013 EDA [Member]
Partnership Equity [Abstract]
Number of common units sold (in shares)	248,252
Gross proceeds from sale of common units	10.7
Dollar amount of Common Units able to sell from Equity Distribution Agreement	200
General partner contributed to maintain general partner ownership percentage	$ 0.3
General partner ownership interest (in hundredths)	2.00%