Equity-Indexed Compensation Plans (Details) shares in Millions	9 Months Ended
	Sep. 30, 2015 $ / shares shares
PAGP LTIP
Outstanding (in shares or units)
Outstanding at beginning of period (in shares or units)	0.1
Outstanding at end of period (in shares or units)	0.1
Weighted Average Grant Date Fair Value per share or unit
Outstanding at beginning of period (in dollars per share or unit) | $ / shares	$ 27.84
Granted (in dollars per share or unit) | $ / shares	27.84
Vested (in dollars per share or unit) | $ / shares	27.84
Outstanding at end of period (in dollars per share or unit) | $ / shares	$ 27.84
PAGP LTIP | Maximum
Outstanding (in shares or units)
Granted (in shares or units)	0.1
Vested (in shares or units)	(0.1)
PAA LTIP
Outstanding (in shares or units)
Outstanding at beginning of period (in shares or units)	7.3
Granted (in shares or units)	1.3
Vested (in shares or units)	(2.1)
Cancelled or forfeited (in shares or units)	(0.3)
Outstanding at end of period (in shares or units)	6.2
Weighted Average Grant Date Fair Value per share or unit
Outstanding at beginning of period (in dollars per share or unit) | $ / shares	$ 41.45
Granted (in dollars per share or unit) | $ / shares	38.91
Vested (in dollars per share or unit) | $ / shares	28.91
Cancelled or forfeited (in dollars per share or unit) | $ / shares	45.68
Outstanding at end of period (in dollars per share or unit) | $ / shares	$ 44.98
Units issued in connection with the settlement of vested awards, net of tax withholding (in units)	0.5
Units withheld for taxes (in units)	0.3
Vested awards settled in cash (in units)	1.3