Subsequent Events - Narrative (Details) $ / shares in Units, shares in Millions, $ in Millions		1 Months Ended	3 Months Ended	9 Months Ended
	Oct. 31, 2019 USD ($) $ / shares shares	Oct. 31, 2019 USD ($) escalate $ / shares MW shares	Sep. 30, 2019 USD ($)	Sep. 30, 2019 USD ($) GW	Nov. 03, 2019 $ / shares
Subsequent Event [Line Items]
Generating capacity | GW				4.4
Subsequent Event
Subsequent Event [Line Items]
Net proceeds received		$ 256.0
Pattern Development 2.0 | Subsequent Event
Subsequent Event [Line Items]
Percent of earnout rights		100.00%
Profits interest in such projects		25.00%
Pattern Development 2.0 | Grady, New Mexico | Subsequent Event
Subsequent Event [Line Items]
Generating capacity | MW		101
Pattern Development 2.0 | Curry Country, New Mexico | Subsequent Event
Subsequent Event [Line Items]
Generating capacity | MW		220
Pattern Development 2.0 | Grady and Curry Country, New Mexico | Subsequent Event
Subsequent Event [Line Items]
Consideration transferred		$ 100.0
Pattern Energy Group LP | Henvey Inlet, Ontario, Canada | Subsequent Event
Subsequent Event [Line Items]
Generating capacity | MW		150
Pattern Energy Group LP | First Nation Reserve No. 2 Lands, Ontario, Canada | Subsequent Event
Subsequent Event [Line Items]
Generating capacity | MW		300
Pattern Energy Group LP | Henvey Inlet First Nation Reserve No. 2 Lands, Ontario, Canada | Subsequent Event
Subsequent Event [Line Items]
Consideration transferred		$ 193.0
Series A | Subsequent Event
Subsequent Event [Line Items]
Aggregate dividend	$ 3.9	$ 3.9
Dividends annualized (in dollars per share) | $ / shares		$ 3.25
Preferred stock, shares issued (in shares) | shares	10.4	10.4
Preferred stock, value, issued	$ 260.0	$ 260.0
Preferred stock, discount		1.50%
Preferred stock, dividend rate		5.625%
Preferred stock, liquidation preference per share | $ / shares	$ 25.00	$ 25.00
Increase in annual dividend rate		0.50%
Maximum number of escalations period | escalate		4
Preferred stock, dividend rate after maximum number of escalations		7.625%
Stock receivable		12.60%
Common Class A | Subsequent Event
Subsequent Event [Line Items]
Dividends payable per share (in dollars per share) | $ / shares	0.4220	$ 0.4220
Dividends annualized (in dollars per share) | $ / shares	$ 1.688
Earnout Acquisition Agreement [Member] | Pattern Energy Group LP | Subsequent Event
Subsequent Event [Line Items]
Purchases from related party		$ 10.0
Merger Agreement
Subsequent Event [Line Items]
Transaction costs			$ 3.0	$ 4.8
Pacific US Inc. | Merger Agreement | Subsequent Event
Subsequent Event [Line Items]
Price per share (in dollars per share) | $ / shares					$ 26.75