Segment Information (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2015 Division		Mar. 31, 2014	Feb. 27, 2015	Dec. 31, 2014
Segment Reporting Information [Line Items]
Number of divisions	2
Sale of commodities	$ 1,402.2		$ 2,085.1
Fees from midstream services	277.5		209.6
Revenues	1,679.7		2,294.7
Operating margin	300.0		275.3
Special GP interest [Abstract]
Goodwill	628.5	[1],[2]		628.5	0
Intangible assets	1,602.4	[2]			591.9
Total assets	13,625.3	[1]	6,055.2		6,453.5
Capital expenditures	157.3		175.4
Business acquisitions	5,047.8
Special GP Interest [Member]
Special GP interest [Abstract]
Goodwill	628.5	[2]
Intangible assets	979.9	[2]
Targa Resources Partners LP [Member]
Segment Reporting Information [Line Items]
Revenues	1,679.7
Operating margin	0
Special GP interest [Abstract]
Total assets	13,439.6	[1]
Capital expenditures	157.3
Business acquisitions	5,047.8
Targa Resources Partners LP [Member] | Special GP Interest [Member]
Special GP interest [Abstract]
Goodwill	628.5	[2]
Intangible assets	979.9	[2]
TRC Non-Partnership [Member]
Segment Reporting Information [Line Items]
Revenues	0		0
Operating margin	(0.1)		0
Special GP interest [Abstract]
Total assets	185.7		78.9
Capital expenditures	0		0
Business acquisitions	0
TRC Non-Partnership [Member] | Special GP Interest [Member]
Special GP interest [Abstract]
Goodwill	0	[2]
Intangible assets	0	[2]
Reportable Segments [Member]
Special GP interest [Abstract]
Total assets	12,016.9	[1]
Reportable Segments [Member] | Targa Resources Partners LP [Member]
Special GP interest [Abstract]
Total assets	11,831.2	[1]
Reportable Segments [Member] | TRC Non-Partnership [Member]
Special GP interest [Abstract]
Total assets	185.7	[1]
Gathering and Processing [Member]
Segment Reporting Information [Line Items]
Number of reportable segments per division	2
Field Gathering and Processing [Member] | Reportable Segments [Member] | Targa Resources Partners LP [Member]
Segment Reporting Information [Line Items]
Revenues	448.7		488.1
Operating margin	79.3		94.1
Special GP interest [Abstract]
Total assets	8,870.2
Coastal Gathering and Processing [Member] | Reportable Segments [Member] | Targa Resources Partners LP [Member]
Segment Reporting Information [Line Items]
Revenues	124.3		285.2
Operating margin	7.8		26.1
Special GP interest [Abstract]
Total assets	352.9
Logistics and Marketing [Member]
Segment Reporting Information [Line Items]
Number of reportable segments per division	2
Logistics Assets [Member] | Reportable Segments [Member] | Targa Resources Partners LP [Member]
Segment Reporting Information [Line Items]
Revenues	188.6		155.9
Operating margin	125.4		96.6
Special GP interest [Abstract]
Total assets	1,764.6
Marketing and Distribution [Member] | Reportable Segments [Member] | Targa Resources Partners LP [Member]
Segment Reporting Information [Line Items]
Revenues	1,332.9		2,155.1
Operating margin	65.9		64.6
Special GP interest [Abstract]
Total assets	487.0
Other Segment [Member] | Targa Resources Partners LP [Member]
Segment Reporting Information [Line Items]
Revenues	21.7		(6.1)
Operating margin	21.7		(6.1)
Special GP interest [Abstract]
Total assets	177.3
Corporate and Eliminations [Member] | Targa Resources Partners LP [Member]
Segment Reporting Information [Line Items]
Revenues	(436.5)		(783.5)
Operating margin	0		0
Special GP interest [Abstract]
Total assets	1,787.6
Operating Segments [Member]
Segment Reporting Information [Line Items]
Sale of commodities	1,402.2		2,085.1
Fees from midstream services	277.5		209.6
Revenues	1,679.7		2,294.7
Operating Segments [Member] | Targa Resources Partners LP [Member]
Segment Reporting Information [Line Items]
Sale of commodities	1,402.2
Fees from midstream services	277.5
Revenues	1,679.7
Operating Segments [Member] | TRC Non-Partnership [Member]
Segment Reporting Information [Line Items]
Sale of commodities	0		0
Fees from midstream services	0		0
Revenues	0		0
Operating Segments [Member] | Field Gathering and Processing [Member] | Reportable Segments [Member] | Targa Resources Partners LP [Member]
Segment Reporting Information [Line Items]
Sale of commodities	168.0		45.8
Fees from midstream services	63.3		40.8
Revenues	231.3		86.6
Special GP interest [Abstract]
Total assets	7,261.8	[1]	3,275.1
Capital expenditures	94.4		98.9
Business acquisitions	5,047.8
Operating Segments [Member] | Field Gathering and Processing [Member] | Reportable Segments [Member] | Targa Resources Partners LP [Member] | Special GP Interest [Member]
Special GP interest [Abstract]
Goodwill	628.5
Intangible assets	979.9
Operating Segments [Member] | Coastal Gathering and Processing [Member] | Reportable Segments [Member] | Targa Resources Partners LP [Member]
Segment Reporting Information [Line Items]
Sale of commodities	52.7		100.5
Fees from midstream services	8.8		7.7
Revenues	61.5		108.2
Special GP interest [Abstract]
Total assets	352.9	[1]	385.1
Capital expenditures	1.1		4.3
Business acquisitions	0
Operating Segments [Member] | Coastal Gathering and Processing [Member] | Reportable Segments [Member] | Targa Resources Partners LP [Member] | Special GP Interest [Member]
Special GP interest [Abstract]
Goodwill	0
Intangible assets	0
Operating Segments [Member] | Logistics Assets [Member] | Reportable Segments [Member] | Targa Resources Partners LP [Member]
Segment Reporting Information [Line Items]
Sale of commodities	27.4		21.0
Fees from midstream services	87.7		68.1
Revenues	115.1		89.1
Special GP interest [Abstract]
Total assets	1,764.6	[1]	1,568.7
Capital expenditures	57.7		68.6
Business acquisitions	0
Operating Segments [Member] | Logistics Assets [Member] | Reportable Segments [Member] | Targa Resources Partners LP [Member] | Special GP Interest [Member]
Special GP interest [Abstract]
Goodwill	0
Intangible assets	0
Operating Segments [Member] | Marketing and Distribution [Member] | Reportable Segments [Member] | Targa Resources Partners LP [Member]
Segment Reporting Information [Line Items]
Sale of commodities	1,132.3		1,924.0
Fees from midstream services	117.7		92.8
Revenues	1,250.0		2,016.8
Special GP interest [Abstract]
Total assets	487.0	[1]	614.1
Capital expenditures	3.0		3.1
Business acquisitions	0
Operating Segments [Member] | Marketing and Distribution [Member] | Reportable Segments [Member] | Targa Resources Partners LP [Member] | Special GP Interest [Member]
Special GP interest [Abstract]
Goodwill	0
Intangible assets	0
Operating Segments [Member] | Other Segment [Member] | Targa Resources Partners LP [Member]
Segment Reporting Information [Line Items]
Sale of commodities	21.7		(6.1)
Fees from midstream services	0		0
Revenues	21.7		(6.1)
Special GP interest [Abstract]
Total assets	177.3	[1]	4.5
Capital expenditures	0		0
Business acquisitions	0
Operating Segments [Member] | Other Segment [Member] | Targa Resources Partners LP [Member] | Special GP Interest [Member]
Special GP interest [Abstract]
Goodwill	0
Intangible assets	0
Operating Segments [Member] | Corporate and Eliminations [Member] | Targa Resources Partners LP [Member]
Segment Reporting Information [Line Items]
Sale of commodities	0.1		(0.1)
Fees from midstream services	0		0.2
Revenues	0.1		0.1
Special GP interest [Abstract]
Total assets	1,787.6	[1]	128.8
Capital expenditures	1.1		0.5
Business acquisitions	0
Operating Segments [Member] | Corporate and Eliminations [Member] | Targa Resources Partners LP [Member] | Special GP Interest [Member]
Special GP interest [Abstract]
Goodwill	0
Intangible assets	0
Intersegment Eliminations [Member]
Segment Reporting Information [Line Items]
Sale of commodities	0		0
Fees from midstream services	0		0
Revenues	0		0
Intersegment Eliminations [Member] | Targa Resources Partners LP [Member]
Segment Reporting Information [Line Items]
Sale of commodities	0
Fees from midstream services	0
Revenues	0
Intersegment Eliminations [Member] | TRC Non-Partnership [Member]
Segment Reporting Information [Line Items]
Sale of commodities	0		0
Fees from midstream services	0		0
Revenues	0		0
Intersegment Eliminations [Member] | Field Gathering and Processing [Member] | Reportable Segments [Member] | Targa Resources Partners LP [Member]
Segment Reporting Information [Line Items]
Sale of commodities	215.4		400.4
Fees from midstream services	2.0		1.1
Revenues	217.4		401.5
Intersegment Eliminations [Member] | Coastal Gathering and Processing [Member] | Reportable Segments [Member] | Targa Resources Partners LP [Member]
Segment Reporting Information [Line Items]
Sale of commodities	62.8		177.0
Fees from midstream services	0		0
Revenues	62.8		177.0
Intersegment Eliminations [Member] | Logistics Assets [Member] | Reportable Segments [Member] | Targa Resources Partners LP [Member]
Segment Reporting Information [Line Items]
Sale of commodities	1.1		0.6
Fees from midstream services	72.4		66.2
Revenues	73.5		66.8
Intersegment Eliminations [Member] | Marketing and Distribution [Member] | Reportable Segments [Member] | Targa Resources Partners LP [Member]
Segment Reporting Information [Line Items]
Sale of commodities	78.5		130.4
Fees from midstream services	4.4		7.9
Revenues	82.9		138.3
Intersegment Eliminations [Member] | Other Segment [Member] | Targa Resources Partners LP [Member]
Segment Reporting Information [Line Items]
Sale of commodities	0		0
Fees from midstream services	0		0
Revenues	0		0
Intersegment Eliminations [Member] | Corporate and Eliminations [Member] | Targa Resources Partners LP [Member]
Segment Reporting Information [Line Items]
Sale of commodities	(357.8)		(708.4)
Fees from midstream services	(78.8)		(75.2)
Revenues	$ (436.6)		$ (783.6)

[1] Corporate assets at the Segment level primarily include investment in unconsolidated subsidiaries and debt issuance costs associated with our long-term debt.

[2] Represents the preliminary acquisition fair value attributable to goodwill and intangible assets associated with the Atlas mergers.