Property and Equipment (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2021	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Property and Equipment
Capitalized interest		$ 18	$ 24	$ 34
Property and equipment, gross		19,292	18,620
Accumulated depreciation		(4,383)	(4,000)
Property and equipment, net		14,909	14,620
Depreciation expense		655	566	528
Impact to net income attributable to PAGP		60	(568)	331
Construction in progress expenditures incurred but not yet paid		$ 48	$ 51	$ 120
Level 3 | Measurement Input, Discount Rate | Valuation Technique, Discounted Cash Flow
Property and Equipment
Discount rate, asset impairment analysis, cost of capital, theoretical market participant			14.00%
Class A Shares
Property and Equipment
Basic net income/(loss) per Class A share (in dollars per share)		$ 0.31	$ (3.06)	$ 1.97
Diluted net income/(loss) per Class A share (in dollars per share)		$ 0.31	$ (3.07)	$ 1.96
Service Life
Property and Equipment
Depreciation expense		$ 72
Impact to net income attributable to PAGP		$ (15)
Service Life | Class A Shares
Property and Equipment
Basic net income/(loss) per Class A share (in dollars per share)		$ (0.08)
Diluted net income/(loss) per Class A share (in dollars per share)		$ (0.08)
Pipelines and related facilities
Property and Equipment
Property and equipment, gross		$ 12,800	$ 11,147
Pipelines and related facilities | Minimum
Property and Equipment
Estimated Useful Lives (in years)		10 years
Pipelines and related facilities | Maximum
Property and Equipment
Estimated Useful Lives (in years)		50 years
Storage, terminal and rail facilities
Property and Equipment
Property and equipment, gross		$ 5,100	6,042
Storage, terminal and rail facilities | Minimum
Property and Equipment
Estimated Useful Lives (in years)		10 years
Storage, terminal and rail facilities | Maximum
Property and Equipment
Estimated Useful Lives (in years)		50 years
Trucking equipment and other
Property and Equipment
Property and equipment, gross		$ 502	524
Trucking equipment and other | Minimum
Property and Equipment
Estimated Useful Lives (in years)		2 years
Trucking equipment and other | Maximum
Property and Equipment
Estimated Useful Lives (in years)		15 years
Construction in progress
Property and Equipment
Property and equipment, gross		$ 248	272
Office property and equipment
Property and Equipment
Property and equipment, gross		$ 312	293
Office property and equipment | Minimum
Property and Equipment
Estimated Useful Lives (in years)		2 years
Office property and equipment | Maximum
Property and Equipment
Estimated Useful Lives (in years)		50 years
Land and other
Property and Equipment
Property and equipment, gross		$ 330	$ 342
Pipeline And Related Facilities And Storage, Terminal And Rail Facilities | Minimum
Property and Equipment
Estimated Useful Lives (in years)			10 years
Pipeline And Related Facilities And Storage, Terminal And Rail Facilities | Minimum | Service Life
Property and Equipment
Estimated Useful Lives (in years)	10 years
Pipeline And Related Facilities And Storage, Terminal And Rail Facilities | Maximum
Property and Equipment
Estimated Useful Lives (in years)			70 years
Pipeline And Related Facilities And Storage, Terminal And Rail Facilities | Maximum | Service Life
Property and Equipment
Estimated Useful Lives (in years)	50 years
Crude Oil | Pipelines and related facilities
Property and Equipment
Non-cash impairment losses, long-lived assets			$ 415
Property and equipment
Property and Equipment
Capitalized interest		6	8	$ 14
(Gains)/losses on asset sales and asset impairments, net
Property and Equipment
Non-cash impairment losses, long-lived assets			$ 541
(Gains)/losses on asset sales and asset impairments, net | Crude Oil | Crude oil storage terminal assets
Property and Equipment
Non-cash impairment losses, long-lived assets		$ 220