Pattern Energy 10-K 1 Mar 19 2018 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($) $ in Billions	12 Months Ended
	Dec. 31, 2018	Feb. 22, 2019	Jun. 30, 2018
Document And Entity Information [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2018
Document Fiscal Year Focus	2,018
Document Fiscal Period Focus	FY
Trading Symbol	PEGI
Entity Registrant Name	Pattern Energy Group Inc.
Entity Central Index Key	1,561,660
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	Yes
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		98,077,874
Entity Public Float			$ 1.5

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Current assets:
Cash and cash equivalents (Note 8)	$ 101	$ 117
Restricted cash (Note 8)	4	9
Counterparty collateral	6	30
Trade receivables (Note 8)	50	55
Derivative assets, current	14	19
Prepaid expenses (Note 8)	18	18
Deferred financing costs, current, net of accumulated amortization of $3 and $3 as of December 31, 2018 and December 31, 2017, respectively	2	1
Other current assets (Note 8)	16	21
Total current assets	211	270
Restricted cash	18	12
Major construction advances	84	0
Construction in progress	259	0
Property, plant and equipment, net (Note 8)	4,119	3,965
Unconsolidated investments	270	311
Derivative assets	9	10
Deferred financing costs	8	8
Net deferred tax assets	5	6
Intangible assets, net (Note 8)	219	136
Goodwill	58	0
Other assets (Note 8)	34	24
Total assets	5,294	4,742
Current liabilities:
Accounts payable and other accrued liabilities (Note 8)	67	54
Accrued construction costs (Note 8)	27	1
Counterparty collateral liability	6	30
Accrued interest (Note 8)	14	17
Dividends payable	42	41
Derivative liabilities, current	2	8
Revolving credit facility, current	198	0
Current portion of long-term debt, net	56	52
Contingent liabilities, current	31	3
Asset retirement obligations, current	24	0
Other current liabilities (Note 8)	11	12
Total current liabilities	478	218
Revolving credit facility	25	0
Long-term debt, net	2,004	1,879
Derivative liabilities	31	21
Net deferred tax liabilities	117	56
Intangible liabilities, net	56	51
Contingent liabilities	142	62
Asset retirement obligations (Note 8)	185	57
Other long-term liabilities (Note 8)	71	50
Advanced lease revenue	26	0
Total liabilities	3,135	2,394
Commitments and contingencies (Note 19)
Equity:
Class A common stock, $0.01 par value per share: 500,000,000 shares authorized; 98,051,629 and 97,860,048 shares outstanding as of December 31, 2018 and December 31, 2017, respectively	1	1
Additional paid-in capital	1,130	1,235
Accumulated loss	(27)	(112)
Accumulated other comprehensive loss	(52)	(26)
Treasury stock, at cost; 223,040 and 157,812 shares of Class A common stock as of December 31, 2018 and December 31, 2017, respectively	(5)	(4)
Total equity before noncontrolling interests	1,047	1,094
Noncontrolling interests	1,112	1,254
Total equity	2,159	2,348
Total liabilities and equity	$ 5,294	$ 4,742

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Statement of Financial Position [Abstract]
Deferred financing costs, current, accumulated amortization	$ 3	$ 3
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	500,000,000	500,000,000
Common stock, shares outstanding (in shares)	98,051,629	97,860,048
Treasury stock, shares (in shares)	(223,040)	(157,812)

Consolidated Statements of Oper

Consolidated Statements of Operations - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Revenue:
Electricity sales	$ 464	$ 402	$ 346
Other revenue	19	9	8
Total revenue	483	411	354
Cost of revenue:
Project expense	143	130	128
Transmission costs	26	19	1
Depreciation, amortization and accretion	250	199	175
Total cost of revenue	419	348	304
Gross profit	64	63	50
Operating expenses:
General and administrative	40	39	35
Related party general and administrative	15	14	10
Impairment expense	7	0	0
Total operating expenses	62	53	45
Operating income	2	10	5
Other income (expense):
Interest expense	(109)	(102)	(78)
Gain (loss) on derivatives	17	(10)	(3)
Earnings in unconsolidated investments, net	1	42	30
Early extinguishment of debt	(6)	(9)	0
Net earnings (loss) on transactions	69	(1)	0
Other income (expense), net	(11)	0	3
Total other expense	(39)	(80)	(48)
Net loss before income tax	(37)	(70)	(43)
Income tax provision	32	12	9
Net loss	(69)	(82)	(52)
Net loss attributable to noncontrolling interests	(211)	(64)	(35)
Net income (loss) attributable to Pattern Energy	$ 142	$ (18)	$ (17)
Weighted average number of common shares outstanding
Basic (in shares)	97,456,407	89,179,343	79,382,388
Diluted (in shares)	97,651,501	89,179,343	79,382,388
Net income (loss) per share attributable to Pattern Energy
Basic (in dollars per share)	$ 1.45	$ (0.20)	$ (0.22)
Diluted (in dollars per share)	1.45	(0.20)	(0.22)
Class A Common Stock
Net income (loss) per share attributable to Pattern Energy
Basic (in dollars per share)			(0.22)
Diluted (in dollars per share)	$ 1.45	$ (0.20)	$ (0.22)

Consolidated Statements of Comp

Consolidated Statements of Comprehensive (Loss) Income - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Statement of Comprehensive Income [Abstract]
Net loss	$ (69)	$ (82)	$ (52)
Other comprehensive income (loss):
Change in foreign currency translation, net of tax impact of zero, $(4) and zero, respectively	(37)	15	5
Cash flow hedge activity:
Change in unrealized losses on cash flow hedges, net of tax impact of $3, ($1) and $1, respectively	(4)	(3)	(7)
Reclassifications to net loss, net of tax impact of $(1), $(1) and $(1), respectively	5	11	7
Total change in cash flow hedge activity	1	8	0
Other comprehensive income related to equity method investee net of tax impact of less than $1 million, $(5) and $(2), respectively	2	14	6
Total other comprehensive income (loss), net of tax	(34)	37	11
Comprehensive loss	(103)	(45)	(41)
Less comprehensive loss attributable to noncontrolling interests, net of tax impact of less than $1 million for all years presented	(219)	(63)	(35)
Comprehensive income (loss) attributable to Pattern Energy	$ 116	$ 18	$ (6)

Consolidated Statements of Co_2

Consolidated Statements of Comprehensive (Loss) Income (Parenthetical) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Statement of Comprehensive Income [Abstract]
Foreign currency translation, tax impact	$ 0	$ 4	$ 0
Effective portion of change in fair market value of derivatives, benefit	3	(1)	1
Reclassifications to net loss, tax impact	(1)	(1)	(1)
Equity method investee, tax impact (less than $1 million)	1	(5)	(2)
Noncontrolling interest, tax impact (less than $1 million)	$ 1	$ 1	$ 1

Consolidated Statement of Stock

Consolidated Statement of Stockholders' Equity - USD ($) $ in Millions	Total	Accumulated Loss	Noncontrolling Interests	Parent Company	Parent CompanyClass A Common Stock	Parent CompanyParent [Member]	Parent CompanyClass A Common StockClass A Common Stock	Parent CompanyTreasury Stock	Parent CompanyAdditional Paid-in Capital	Parent CompanyAccumulated Loss	Parent CompanyAccumulated Other Comprehensive Income (Loss)
Beginning balance at Dec. 31, 2015	$ 1,776		$ 944			$ 832	$ 1	$ (2)	$ 983	$ (77)	$ (73)
Beginning balance, shares (in shares) at Dec. 31, 2015							74,709,442	(65,301)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of Class A common stock, net of issuance costs	286					286			286
Issuance of Class A common stock, net of issuance, shares (in shares)							12,540,504
Issuance of Class A common stock under equity incentive award plan, net	0
Issuance of Class A common stock under equity incentive award plan, net, shares (in shares)							271,705
Repurchase of shares for employee tax withholding	(1)					(1)		$ (1)
Repurchase of shares for employee tax withholding, shares (in shares)								(45,663)
Stock-based compensation	5					5			5
Dividends declared ($1.69 per Class A common share)	(128)					(128)			(128)
Distributions to noncontrolling interests	(18)	$ 0	(18)
Net loss	(52)		(35)	$ (17)						(17)
Other comprehensive income, net of tax	11			11							11
Ending balance, shares (in shares) at Dec. 31, 2016							87,521,651	(110,964)
Ending balance at Dec. 31, 2016	1,879		891			988	$ 1	$ (3)	1,146	(94)	(62)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of Class A common stock, net of issuance costs	237					237			237
Issuance of Class A common stock, net of issuance, shares (in shares)							10,268,261
Issuance of Class A common stock under equity incentive award plan, net	0
Issuance of Class A common stock under equity incentive award plan, net, shares (in shares)							227,948
Repurchase of shares for employee tax withholding	(1)					(1)		$ (1)
Repurchase of shares for employee tax withholding, shares (in shares)								(46,848)
Stock-based compensation	5					5			5
Dividends declared ($1.69 per Class A common share)	(151)					(151)			(151)
Acquisitions	390	0	390
Distributions to noncontrolling interests	(20)	0	(20)
Partial sale of subsidiary	54	0	56			(2)			(2)
Net loss	(82)		(64)	(18)						(18)
Other comprehensive income, net of tax	$ 37		1	36							36
Ending balance, shares (in shares) at Dec. 31, 2017	97,860,048				97,860,048		98,017,860	(157,812)
Ending balance at Dec. 31, 2017	$ 2,348		1,254	1,093		1,094	$ 1	$ (4)	1,235	(112)	(26)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Issuance of Class A common stock under equity incentive award plan, net	0
Issuance of Class A common stock under equity incentive award plan, net, shares (in shares)							256,809
Repurchase of shares for employee tax withholding	(1)					(1)		$ (1)
Repurchase of shares for employee tax withholding, shares (in shares)								(65,228)
Stock-based compensation	4					4			4
Dividends declared ($1.69 per Class A common share)	(166)					(166)			(109)	(57)
Acquisitions	49	0	49
Sale of subsidiaries	(32)		(32)
Contribution from noncontrolling interests	98	0	98
Distributions to noncontrolling interests	(38)	0	(38)
Partial sale of subsidiary		$ 5	(32)
Net loss	(69)		(211)	141		142				142
Other comprehensive income, net of tax	$ (34)		(8)	(26)		(26)					(26)
Ending balance, shares (in shares) at Dec. 31, 2018	98,051,629				98,051,629		98,274,669	(223,040)
Ending balance at Dec. 31, 2018	$ 2,159		$ 1,112	$ 1,047		$ 1,047	$ 1	$ (5)	$ 1,130	$ (27)	$ (52)

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Operating activities
Net loss	$ (69)	$ (82)	$ (52)
Adjustments to reconcile net loss to net cash provided by operating activities:
Depreciation, amortization and accretion	280	215	189
Impairment expense	7	0	0
Loss on derivatives	4	16	22
Stock-based compensation	5	5	5
Deferred taxes	16	15	8
Earnings in unconsolidated investments, net	(1)	(41)	(30)
Distribution from unconsolidated investments	(48)	(54)	(15)
Gain on transactions	(71)	0	0
Early extinguishment of debt	6	9	0
Other reconciling items	1	(5)	(4)
Changes in operating assets and liabilities:
Counterparty collateral asset	24	14	(44)
Trade receivables	1	(10)	8
Other current assets	15	(14)	(4)
Other assets (non-current)	(6)	2	1
Accounts payable and other accrued liabilities	3	18	(3)
Counterparty collateral liability	(24)	(14)	44
Advanced lease revenue	34	0	0
Other current liabilities	26	15	2
Other long-term liabilities	(20)	21	7
Net cash provided by operating activities	279	218	164
Investing activities
Cash paid for acquisitions and investments, net of cash and restricted cash acquired	(415)	(297)	(136)
Proceeds from sale of investments, net of cash and restricted cash distributed	214	0	0
Capital expenditures	(181)	(44)	(33)
Distribution from unconsolidated investments	10	13	42
Other assets	(1)
Other assets		8	3
Net cash used in investing activities	(373)	(320)	(124)
Financing activities
Proceeds from public offering, net of issuance costs	0	237	286
Dividends paid	(165)	(145)	(120)
Capital contributions - noncontrolling interests	98	0	0
Capital distributions - noncontrolling interests	(38)	(20)	(18)
Payment for financing fees	(9)	(16)	0
Proceeds from short-term debt	562	333	175
Repayment of short-term debt	(402)	(513)	(350)
Proceeds from long-term debt and other	226	694	0
Repayment of long-term debt and other	(186)	(483)	(48)
Proceeds (payments) for termination of designated derivatives	1	(14)	0
Disposition of controlling interest, net	0	58	0
Other financing activities	(4)	(6)	(2)
Net cash provided by (used in) financing activities	83	125	(77)
Effect of exchange rate changes on cash, cash equivalents and restricted cash	(4)	6	0
Net change in cash, cash equivalents and restricted cash	(15)	29	(37)
Cash, cash equivalents and restricted cash at beginning of period	138	109	146
Cash, cash equivalents and restricted cash at end of period	123	138	109
Supplemental disclosures
Cash payments for income taxes	2	0	0
Cash payments for interest expense	97	86	70
Schedule of non-cash activities
Change in property, plant and equipment	224	2	1
Change in additional paid-in capital	$ 0	$ (2)	$ 0

Organization

Organization	12 Months Ended
	Dec. 31, 2018
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization	Organization Pattern Energy Group Inc. (Pattern Energy or the Company) is a vertically integrated renewable energy company with a mission to transform the world to renewable energy. Our business consists of (i) an operating business segment which is comprised of a portfolio of high-quality renewable energy power projects located in many attractive markets that produces long-term stable cash flows and (ii) ownership interests in an upstream development platform aligned with our operating business which provides us access to a pipeline of projects and potential for higher returns through project development. The Company holds ownership interests in 24 renewable energy projects with an operating capacity that totals approximately 4 gigawatts (GW) which are located in the United States, Canada and Japan. Pattern Energy was organized in the state of Delaware in October 2012. The Company issued 100 shares in October 2012 to Pattern Renewables LP, a 100% owned subsidiary of Pattern Energy Group LP and subsequently in October 2013 conducted an initial public offering.

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2018
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Summary of Significant Accounting Policies Basis of Presentation and Principles of Consolidation The accompanying consolidated financial statements have been prepared in accordance with the accounting principles generally accepted in the United States (U.S. GAAP). They include the results of wholly-owned and partially-owned subsidiaries in which the Company has a controlling interest with all significant intercompany accounts and transactions eliminated. Use of Estimates The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, disclosures of contingent assets and liabilities at the date of the financial statements, and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates, and such differences may be material to the consolidated financial statements. Out-of-Period Adjustment During the year ended December 31, 2018, the Company identified a $1 million error in tax expense related to the recognition of net operating loss carryforwards in its Chilean entity. The Company concluded the error was not material to any previously reported period and is not material to the year ended December 31, 2018. The Company recorded the error as an out-of-period adjustment in the year ended December 31, 2018. Cash and Cash Equivalents Cash and cash equivalents consist of cash in banks and highly liquid investments with original maturities of three months or less. Restricted Cash Restricted cash consists of cash balances which are restricted as to withdrawal or usage and includes cash to collateralize bank letters of credit related primarily to transmission interconnection rights, power sale agreements (PSA) and for certain reserves required under the Company’s loan agreements. Reconciliation of Cash and Cash Equivalents and Restricted Cash as presented on the Statements of Cash Flows The following table provides a reconciliation of cash, cash equivalents, and restricted cash reported within the consolidated balance sheets that sum to the total of the same such amounts shown in the consolidated statements of cash flows (in millions): December 31, 2018 2017 2016 Cash and cash equivalents $ 101 $ 117 $ 84 Restricted cash - current 4 9 12 Restricted cash 18 12 13 Cash, cash equivalents and restricted cash shown in the consolidated statements of cash flows $ 123 $ 138 $ 109 Counterparty Collateral and Collateral Liability As a result of a counterparty's credit rating downgrade, the Company received collateral related to an energy derivative agreement, as discussed in Note 12 , Derivative Instruments . The Company does not have the right to pledge, invest, or use the collateral for general corporate purposes. As of December 31, 2018 , the Company has recorded a current asset of approximately $6 million to counterparty collateral and a current liability of approximately $6 million to counterparty collateral liability representing the collateral received and corresponding obligation to return the collateral, respectively. Trade Receivables The Company’s trade receivables are generated by selling energy and renewable energy credits primarily to creditworthy utilities and large commercial companies. The Company believes that all amounts are collectible and an allowance for doubtful accounts is not required as of December 31, 2018 and 2017 . Although PG&E and PREPA, offtakers for Hatchet Ridge and Santa Isabel, respectively, have filed for reorganization and debt restructuring, the Company has assessed and determined that trade receivables at Hatchet Ridge and Santa Isabel were not impaired as of December 31, 2018. Major Construction Advances Major construction advances represent advances to (i) suppliers for the manufacture of wind turbines, transmission lines, and solar panels in accordance with component equipment supply agreements and (ii) builders in accordance with plant construction contracts. These construction advances are reclassified to construction in progress when the Company takes legal title to the equipment. Derivatives The Company may enter into interest rate swaps, interest rate caps, forwards and other agreements to manage its interest rate, electricity price and foreign exchange rate risk. The Company recognizes its derivative instruments as assets or liabilities at fair value in the consolidated balance sheets, unless the derivative instruments qualify for the "normal purchase normal sale" (NPNS) scope exception to derivative accounting. Contracts used in normal business operations that are settled by physical delivery, among other criteria, are eligible for and may be designated as NPNS. NPNS contracts do not meet the definition of derivatives, and therefore, contracts associated with the sale of energy are recognized as electricity sales when revenue recognition criteria are met and contracts associated with the production of electricity are recognized as project expense when incurred on the consolidated statements of operations. The Company does not have contracts subject to master netting agreements with counterparties, as such assets and liabilities are presented gross on the consolidated balance sheets. Accounting for changes in the fair value of a derivative instrument depends on whether it has been designated as part of a hedging relationship and on the type of hedging relationship. For derivative instruments that qualify and are designated as cash flow hedges, the change in unrealized losses on cash flow hedges, net of tax is reported as a component of other comprehensive income (loss) (OCI), and is reclassified into earnings in the same period or periods during which the hedged transaction affects earnings. The ineffective portion of change in fair value is recorded as a component of net income (loss) on the consolidated statements of operations. The Company discontinues hedge accounting for its cash flow hedges prospectively when it has determined that the hedging relationship has materially changed since its inception or when the hedging instrument is no longer considered highly effective at offsetting the hedged risk. If the hedged transaction is no longer probable of occurring, any gain or loss previously deferred in OCI will be immediately recognized into earnings. If hedge accounting is discontinued for any other reason, any previously deferred gain or loss will remain in OCI and amortized into earnings as the hedged transaction affects future earnings. For undesignated derivative instruments, the change in fair value is reported as a component of net income (loss) on the consolidated statements of operations. Fair Value of Financial Instruments Accounting Standards Codification (ASC) 820, Fair Value Measurement , defines fair value as the price at which an asset could be exchanged or a liability transferred in an orderly transaction between knowledgeable, willing parties in the principal or most advantageous market for the asset or liability. Where available, fair value is based on observable market prices or derived from such prices. Where observable prices or inputs are not available, valuation models are applied which may involve some level of management estimation and judgment, the degree of which is dependent on the price transparency for the instruments or market and the instruments’ complexity. See Note 14 , Fair Value Measurement . Deferred Financing Costs Financing costs incurred with securing a construction loan are recorded in the Company’s consolidated balance sheets as an offset to the construction loan and amortized over the contractual life of the loan to construction in progress using the effective interest method. Financing costs incurred with securing a term loan are recorded in the Company’s consolidated balance sheets as an offset to the term loan and amortized to interest expense in the Company’s consolidated statements of operations over the contractual life of the loan using the effective interest method. If the term loan has not been drawn on, financing costs incurred with securing the term loan are recorded in the Company’s consolidated balance sheets as an asset. Financing costs related to a revolving credit facility or a letter of credit facility are recorded in the Company’s consolidated balance sheets as an asset and amortized to interest expense in the Company’s consolidated statements of operations on a straight-line basis over the contractual term of the arrangement. Construction in Progress Construction in progress represents the accumulation of project development costs and construction costs, including the costs incurred for the purchase of major equipment such as turbines for which the Company has taken legal title, civil engineering, electrical and other related costs. Other capitalized costs include reclassified deferred development costs, amortization of intangible assets, amortization of deferred financing costs, capitalized interest and other costs required to place a project into commercial operation. Deferred development costs represent the accumulated costs of initial permitting, environmental reviews, land rights and obligations and preliminary design and engineering work. The Company expenses all project development costs until a project is determined to be technically feasible and likely to achieve commercial success, typically when a power purchase agreement has been negotiated. The Company begins capitalizing deferred development costs as a component of construction in progress on the date the project commences construction. Once the project achieves commercial operation, the Company reclassifies the amounts recorded in construction in progress to property, plant and equipment. Property, Plant and Equipment Property, plant and equipment represents the costs of completed and operational projects transferred from construction in progress, as well as other costs incurred for purchasing assets such as land, computer equipment and software, furniture and fixtures, leasehold improvements and other equipment. Property, plant and equipment are stated at cost, less accumulated depreciation. Depreciation is calculated using the straight-line method over the respective assets’ useful lives. Wind farms for which construction began before 2011 are depreciated over 20 years and wind farms for which construction began after 2011 are depreciated over 25 to 30 years . Solar facilities are depreciated over 25 years . Transmission assets are depreciated over 50 years . The remaining assets are depreciated over two to five years. Improvements to property, plant and equipment deemed to extend the useful economic life of an asset are capitalized. Repair and maintenance costs are expensed as incurred. Intangible Assets and Intangible Liabilities Long-lived intangible assets and intangible liabilities primarily include power purchase agreements (PPAs), land easements, land options, tax savings and mining rights. PPAs obtained through acquisitions are valued as of the acquisition date and the difference between the contract price and the estimated fair value is recorded as an intangible asset or liability. If the contract price is higher than the estimated fair value, the Company will recognize an intangible asset. If the contract price is lower than the estimated fair value, the Company will recognize an intangible liability. Land easements, land options and mining rights are recognized at the carryover basis from the seller as their carrying costs approximate fair value. The Company generally amortizes PPAs using the straight-line method over the remaining term of the related PPA. The Company amortizes land easements, land options, tax savings and mining rights using the straight-line method over the term of their estimated useful lives, which represents the term of the land easements, land option, tax savings and mining rights agreements, ranging from approximately 9 to 50 years . The Company periodically evaluates whether events or changes in circumstances have occurred that indicate the carrying amount of long-lived intangible assets may not be recoverable, or information indicates that impairment may exist. Accounting for Impairment of Long-Lived Assets The Company periodically evaluates long-lived assets for potential impairment whenever events or changes in circumstances have occurred that indicate that impairment may exist, or the carrying amount of the long-lived asset may not be recoverable. An impairment loss is recognized only if the carrying amount of a long-lived asset is not recoverable based on its estimated future undiscounted cash flows. An impairment loss is calculated based on the excess of the carrying value of the long-lived asset over the fair value of such long-lived asset, with the fair value determined based on an estimate of discounted future cash flows. If the Company meets the criteria for assets held for sale, to calculate the fair value of the assets less costs to sell, the Company considers factors including current sales prices and any recent legitimate offers. If the estimated fair value less costs to sell of an asset is less than its current carrying value, the asset is written down to its estimated fair value less costs to sell. Due to uncertainties in the estimation process, it is possible that actual results could differ from the estimates used in the Company's historical analysis. The Company's assumptions about project sale prices require significant judgment because the current market is highly sensitive to changes in economic conditions. The Company estimates the fair values of assets held for sale based on current market conditions and assumptions made by management, which may differ from actual results and may result in additional impairments if market conditions deteriorate. When assets are classified as held for sale, the Company does not continue to record depreciation or amortization for the respective assets. For the year ended December 31, 2018, the Company recognized impairment expense of $7 million related to the sale of the Company's Chilean entities. See Note 4 , Divested Operations. Goodwill The Company records goodwill when the purchase price of an acquired business exceeds its fair value as of the acquisition date. Goodwill is not amortized, but is subject to an assessment for impairment at least annually in the fourth quarter or more frequently if events occur or circumstances change that will more likely than not reduce the fair value of the reporting unit below its carrying amount. The Company may first assess goodwill for qualitative factors to determine whether it is necessary to perform a quantitative impairment test. The qualitative analysis considers entity-specific and macroeconomic factors and their potential impact on the key assumptions used in the determination of the fair value of the reporting unit. A quantitative impairment test is performed if the results of the qualitative assessment indicate that it is more likely than not that the fair value of the reporting unit is less than its carrying value, or if a qualitative assessment is not performed. Quantitative tests compare the fair value of the asset to its carrying value. Variable Interest Entities VIEs are entities that do not qualify for a scope exception from the variable interest model and are therefore subject to consolidation under the variable interest model. An entity is considered to be a VIE if (1) the entity does not have enough equity to finance its own activities without additional support, (2) the entity’s at-risk equity holders lack the characteristics of a controlling financial interest, or (3) the entity is structured with non-substantive voting rights. ASC 810, Consolidation , defines the criteria for determining the existence of VIEs and provides guidance for consolidation. The Company consolidates VIEs where the Company is the primary beneficiary. The primary beneficiary of a VIE is the party that has the power to direct the activities that most significantly impact the performance of the entity and the obligation to absorb losses or the right to receive benefits that could potentially be significant to the entity. To the extent the entity does not meet the definition of a VIE, the ASC 810 guidance for voting interest entities (VOEs) is applied. The usual condition for a controlling financial interest, and therefore consolidation by the Company, is ownership of a majority voting interest of a corporation or a majority of kick-out rights for a limited partnership. To the extent the entity is not consolidated under the VIE or VOE models, the Company uses the equity method of accounting. These amounts are included in unconsolidated investments in the consolidated balance sheets. Acquisitions Accounting Standards Update (ASU) 2017-01, Clarifying the Definition of a Business (ASU 2017-01) provides a screen test to determine when a set of assets and activities should not be considered a business. Under ASU 2017-01, the Company will perform an initial screening test as of the acquisition date that, if met, results in the conclusion that the set is not a business. If the initial screening test is not met, the Company evaluates whether the set is a business based on whether there are inputs and a substantive process in place. The definition of a business impacts whether the Company consolidates an acquisition under business combination guidance or asset acquisition guidance. When the Company's acquisition is recognized as an equity method investment, the definition of a business impacts whether equity method goodwill can be recognized. Business Combinations The Company accounts for its business combinations by recognizing the identifiable assets acquired, the liabilities assumed, and any non-controlling interest in the acquiree at the acquisition date. The purchase is accounted for using the acquisition method, and the fair value of purchase consideration is allocated to the tangible and intangible assets acquired and the liabilities assumed, based on their estimated fair values. Contingent consideration is also recognized and measured at fair value as of the acquisition date. The excess, if any, of the fair value of the purchase consideration over the fair values of the identifiable net assets is recorded as goodwill. Conversely, the excess, if any, of the net fair values of the identifiable net assets over the fair value of the purchase consideration is recorded as a gain. Such valuations require management to make significant estimates and assumptions, especially with respect to intangible assets. These estimates and assumptions are inherently uncertain, and as a result, actual results may differ from estimates. Significant estimates include, but are not limited to, future expected cash flows, useful lives and discount rates. During the measurement period, which is up to one year from the acquisition date, we may record adjustments to the assets acquired and liabilities assumed, with a corresponding offset to either goodwill or gain, depending on whether the fair value of purchase consideration is in excess of or less than net assets acquired. Upon the conclusion of the measurement period, any subsequent adjustments are recorded to earnings. Transaction costs associated with business combinations are expensed as incurred. Asset Acquisitions When the Company acquires assets and liabilities that do not constitute a business or a VIE of which the Company is the primary beneficiary , the fair value of the purchase consideration, including the transaction costs of the asset acquisition, is assumed to be equal to the fair value of the net assets acquired. The purchase consideration, including the transaction costs, is allocated to the individual assets and liabilities assumed based on their relative fair values. Contingent consideration associated with the acquisition is generally recognized only when the contingency is resolved. No goodwill is recognized in an asset acquisition. When the Company acquires assets and liabilities that do not constitute a business but meet the definition of a VIE of which the Company is the primary beneficiary, the purchase is accounted for using the acquisition method described above for business combinations, except that no goodwill is recognized. To the extent that there is difference between the purchase consideration and the VIE's identifiable assets and liabilities recorded and measured at fair value, the difference is recognized as a gain or loss. Equity Method Investments When the Company acquires a noncontrolling interest in an entity where it is not the primary beneficiary, does not control any of the ongoing activities of the entity, and does not meet consolidation requirements of ASC 810 and ASU 2015-02 , Consolidation (Topic 810): Amendments to the Consolidation Analysis, the investment is initially recognized as an equity method investment at cost. Any difference between the cost of an investment and the amount of underlying equity in net assets of an investee are considered basis differences. Basis differences related to the property, plant and equipment are amortized over the estimated economic useful life of the underlying long-lived assets while basis differences related to the PPA are amortized over the remaining term of the PPA. Transactions costs associated with equity method investments are included in the investment. When the Company receives distributions in excess of the carrying value of its investment, and the Company is not liable for the obligations of the investee nor otherwise committed to provide financial support, the Company recognizes such excess distributions as equity method earnings in the period the distributions occur. Additionally, when the Company's carrying value in an unconsolidated investment is zero and the Company is not liable for the obligations of the investee nor otherwise committed to provide financial support, the Company will not recognize equity in earnings (losses) or equity in other comprehensive income of unconsolidated investments. When the investee subsequently reports income, the Company does not record its share of such income until it equals the amount of distributions in excess of the carrying value that were previously recognized in income and previously unrecognized losses. During the years ended December 31, 2018, 2017 and 2016, the Company had no such obligations, commitments or requirements to provide additional funding for unconsolidated investments with carrying values below zero during such years. Profits or losses related to intra-entity transactions with an equity method investment are eliminated until realized by the Company. As a result, equity income or loss reported on the Company's income statement for certain unconsolidated investments may differ from a mathematical calculation of net income or loss attributable to the Company's equity interest based upon the factor of its equity interest and the net income or loss attributable to equity owners as shown on investee companies' income statements. To the extent that cumulative comprehensive income exceeds cumulative distributions received, the Company records the distribution as distributions from unconsolidated investments on the Company's consolidated statements of cash flows within operating cash flows. All other distributions are recorded as distributions from unconsolidated investments on the Company's consolidated statements of cash flows within investing activities. Noncontrolling Interests Noncontrolling interests represent the portion of the Company’s net income (loss), net assets and comprehensive income (loss) that is not allocable to the Company and is calculated based on ownership percentage, for applicable projects. For the noncontrolling interests in the Company’s Panhandle 1, Panhandle 2, Post Rock, Logan's Gap, Amazon Wind, Broadview Holdings, and Stillwater, the Company has determined that the operating partnership agreements do not allocate economic benefits pro rata to its two classes of investors and the appropriate methodology for calculating the noncontrolling interest balance that reflects the substantive profit sharing arrangement is a balance sheet approach using the hypothetical liquidation at book value (HLBV) method. Under the HLBV method, the amounts reported as noncontrolling interest in the consolidated balance sheets and consolidated statements of operations represent the amounts the third party would hypothetically receive at each balance sheet reporting date under the liquidation provisions of the operating partnership agreement assuming the net assets of the projects were liquidated at recorded amounts determined in accordance with U.S. GAAP and distributed to the investors. The noncontrolling interest in the results of operations and comprehensive income (loss) is determined as the difference in noncontrolling interests in the consolidated balance sheets at the start and end of each reporting period, after taking into account any capital transactions between the projects and the third party. The noncontrolling interest balances in the projects are reported as a component of equity in the consolidated balance sheets. Asset Retirement Obligation The Company records asset retirement obligations (AROs) for the estimated costs of decommissioning turbines, removing above-ground installations and restoring sites, at the time when a contractual decommissioning obligation is incurred. AROs represent the present value of the expected costs and timing of the related decommissioning activities. The ARO assets and liabilities are recorded in property, plant and equipment and other long-term liabilities, respectively, in the consolidated balance sheets. The Company records accretion expense, which represents the increase in the asset retirement obligations, over the remaining or operational life of the associated wind project. Accretion expense is recorded as cost of revenue in the consolidated statements of operations using accretion rates based on credit adjusted risk-free interest rates. Changes resulting from revisions to the timing or amount of the original estimate of cash flows are recognized as an increase or a decrease in the asset retirement cost, or income when the asset retirement cost is depleted. Accounting for Re-powering The Company's commitment to a plan to re-power a project represents the decision to abandon the existing long-lived asset. The decision to abandon a long-lived asset is viewed as an indicator of impairment, and as such a recoverability test is required. If the recoverability test indicates that the carrying value is not recoverable, the fair value of the existing asset is compared to its net carrying value. If the fair value of the asset is less than its net carrying value, an impairment expense for the difference is recorded. The remaining useful life of the existing asset represents the period between the date the Company is committed to a plan to abandon the asset and the removal date. Due to the change in useful life, the Company will revise the estimated future cash flows of the asset retirement obligation. As a result, the Company will accelerate depreciation expense and accretion expense. In 2018, the Company committed to a plan to repower its Gulf Wind facility, as such the Company performed a recoverability test. The Company passed the recoverability test and did not recognize an impairment. However, beginning in the fourth quarter of 2018, the Company revised the depreciable life for the portion of the Gulf Wind facility it expects to abandon to approximately 15 months . As of December 31, 2018, the Company's construction start date is not finalized and, as such the future depreciation rate may be adjusted as the timing of construction becomes more certain. Contingent Liabilities Contingent obligations that are acquired through business combinations are initially recorded at fair value on the date of acquisition while contingent obligations that are acquired through asset acquisitions are recorded when the contingency is resolved. Subsequent to the initial recognition of contingent obligations accounted for as a business combination, the Company accounts for these contingent obligations in a systematic and rational method in accordance with ASC 450, Contingencies. The Company’s contingent liabilities related to turbine availability warranties with turbine manufacturers and turbine availability guarantees associated with long-term turbine service arrangements are reported at net realizable value. Pursuant to these warranties and guarantees, if a turbine operates at less than minimum availability during the warranty or guarantee period, the manufacturer or service provider is obligated to pay, as liquidated damages, an amount for each percent that the turbine operates below the minimum availability threshold at the end of the warranty period. However, the Company does not recognize liquidated damages that remain contingent until the end of the warranty period. In addition, pursuant to certain of these warranties and guarantees, if a turbine operates at more than a specified availability during the warranty or guarantee period, the Company has an obligation to pay a bonus to the turbine manufacturer or service provider at the end of the warranty period. The Company records contingent liabilities at each reporting period associated with these bonuses expected to be paid at the end of the warranty period. Advanced lease revenue Advanced lease revenue presented on the consolidated balance sheets represents advance payments the Company has received under a power purchase agreement. As the power purchase agreement is an operating lease, the advanced lease payments will be recorded as lease revenue on a straight-line basis over the 25-year term of the agreement. Concentrations of Credit Risk Financial instruments that potentially subject the Company to concentrations of credit risk consist primarily of cash and cash equivalents, trade receivables, reimbursable interconnection costs and derivative instruments. The Company’s cash and cash equivalents are with high quality institutions. The Company has exposure to credit risk to the extent cash and cash equivalent balances, including restricted cash, exceed amounts covered by federal deposit insurance; however, the Company believes that its credit risk is immaterial. In addition, reimbursable interconnection costs are with large creditworthy utility companies and the Company’s derivative instruments are placed with counterparties that are creditworthy institutions. The Company generally does not require collateral. Although PG&E and PREPA, offtakers for Hatchet Ridge and Santa Isabel, respectively, have filed for reorganization and debt restructuring, the Company has assessed and determined that trade receivables at Hatchet Ridge and Santa Isabel were not impaired as of December 31, 2018. The table below presents significant customers who accounted for greater than 10% of total revenue, PREPA and PG&E for the years ended December 31, 2018 , 2017 and 2016 : Year ended December 31, 2018 2017 2016 Revenue Revenue Revenue Morgan Stanley Capital Group Inc. 7.2 % 9.1 % 10.9 % PG&E 5.3 % 6.8 % 8.5 % PREPA 4.1 % 4.2 % 6.0 % San Diego Gas & Electric 12.2 % 13.4 % 14.6 % Southern California Edison Company 11.9 % 5.8 % — % Revenue Recognition Beginning in 2018, the Company adopted ASC 606 Revenue Recognition (ASC 606). See Note 3, Revenue, regarding our revenue recognition policy . The Company sells electricity and related RECs under the terms of PSAs, PPAs or at market prices. Revenue is recognized based upon the amount of electricity delivered at rates specified under the contracts, or at market prices for spot market transactions, assuming all other revenue recognition criteria are met. When renewable energy credits are sold as a separate component, revenue is recognized at the time title to the energy credits is transferred to the buyer. Depending on the terms of the PSA, the Company may account for the contracts as operating leases pursuant to ASC 840, Leases (ASC 840), or derivative instruments pursuant to ASC 815, Derivatives and Hedging (ASC 815). In considering ASC 840, it was determined that certain of the Company's PPAs are operating leases. ASC 840 requires minimum lease payments to be recognized over the term of the lease and contingent rents to be recorded when the achievement of the contingency becomes probable. All energy sales under the PPAs, which are considered leases, are contingent rent due to the inherent

Revenue

Revenue	12 Months Ended
	Dec. 31, 2018
Revenue from Contract with Customer [Abstract]
Revenue	Revenue The Company sells electricity and related RECs under the terms of PSAs or at market prices. Depending on the terms of the PSAs, the Company may account for the contracts as operating leases pursuant to ASC 840, derivative instruments pursuant to ASC 815 or contracts with customers pursuant to Topic 606 (as defined below). A majority of the Company's revenues are accounted for under ASC 840 or ASC 815. On January 1, 2018, the Company adopted the new accounting standard ASC 606, Revenue from Contracts with Customers , and all the related amendments (Topic 606) and applied Topic 606 to its PSA contracts previously accounted for under Topic 605, using the modified retrospective method. Results of the reporting period beginning January 1, 2018 are presented under Topic 606, while prior period amounts are not adjusted and continue to be reported in accordance with the Company's historic accounting under Topic 605. The Company did not record any adjustment to the opening retained earnings as of January 1, 2018 as a result of adopting Topic 606. Additionally, the adoption of Topic 606 does not materially change the presentation of revenue. Revenue Recognition Revenues from contracts with customers are recognized when control of promised goods and services is transferred to customers, in an amount that reflects the consideration the Company expects to be entitled to in exchange for those goods or services. The following table presents the Company's total revenue recognized and, for revenue from contracts with customers, disaggregated by revenue sources (in millions): Year ended December 31, 2018 2017 (1) 2016 (1) Revenue from contracts with customers Electricity sales Electricity sales under PSA $ 74 $ 65 $ 69 Electricity sales to market 14 21 16 REC sales 7 7 5 Electricity sales from contracts with customers 95 93 90 Other revenue Related party management service fees 8 7 5 Other revenue from contracts with customers 8 7 5 Total revenue from contracts with customers 103 100 95 Other electricity sales (2) 369 309 257 Other revenue 11 2 2 Total revenue $ 483 $ 411 $ 354 (1) As noted above, prior period amounts have not been adjusted under the modified retrospective method. (2) Includes revenue from PSAs accounted for as leases and energy hedge contracts. Electricity Sales The Company generates revenues primarily by delivering electricity to customers under PSAs and market participants. The revenues are primarily determined by the price of the electricity under the PSAs or market price multiplied by the amount of electricity that the Company delivers. The Company transfers control of the electricity over time and the customer simultaneously receives and consumes the benefits provided by the Company's performance as it performs. Accordingly, the Company has concluded that the sale of electricity over the term of the agreement represents a series of distinct goods that are substantially the same and that have the same pattern of transfer to the customer. Each distinct transfer of electricity in MWh that the Company promises to transfer to the customer meets the criteria to be a performance obligation satisfied over time. The electricity sales are recognized based on an output measure, as each MWh is delivered to the customers. The Company recognizes revenue based on the amount metered and invoiced on the basis of the contract prices multiplied by MWh delivered. The Company does not determine the total transaction price at contract inception, allocate the transaction price to performance obligations, or disclose the value of the variable portion of the remaining performance obligations for contracts for which it recognizes revenue as invoiced. Renewable Energy Credits Sales Each promise to deliver RECs is a distinct performance obligation that is satisfied at a point in time as none of the criteria are met to account for such promise as performance obligation satisfied over time. The Company either delivers RECs with electricity under PSAs or on a standalone basis (in a contract that does not include electricity). When RECs are sold on a standalone basis, the revenue related to the RECs is recognized at the point in time at which control of the energy credits is transferred to customers. RECs delivered under PSAs with electricity are immaterial in the context of the contracts with customers and therefore not separately accounted for. Remaining performance obligations represent the transaction price of standalone RECs for which RECs have not been delivered to the customer's account. The transaction price is determined on the basis of the stated contract price multiplied by RECs to be delivered. As of December 31, 2018 , approximately $20 million of revenue is expected to be recognized from remaining performance obligations associated with existing contracts for the standalone sale of RECs. The Company expects to recognize revenue on approximately 61% of these remaining performance obligations over the next 24 months, with the balance recognized thereafter. Related Party Management Service Fees Related party revenue management service fees represent revenue recognized from the services provided by the Company, under Management, Operations and Maintenance Agreements (MOMAs) and Project Administration Agreements (PAAs) with certain wind farms that are consolidated subsidiaries of Pattern Development Companies or entities the Company accounts for as equity investments. Under these agreements, the Company provides services to the various wind farms, typically for a fixed annual fee payable in monthly installments, which escalates with the consumer price index (CPI) on an annual basis. The services provided by the Company to the wind farm under the agreement each month represent a single performance obligation, which is delivered to the project over time and is invoiced at a fixed price per month and will be recognized over time as invoiced to the respective wind farm. Remaining performance obligations represent the fixed monthly installments for which services have not been performed. The transaction price is determined on the basis of the stated contract price. Transaction Price Allocated to the Remaining Performance Obligations The Company expects to recognize revenue under PSAs and related party management service fees in the following amounts related to fixed consideration associated with remaining performance obligations in each of the future periods noted as of December 31, 2018 (in millions): Amount 2019 $ 79 2020 66 2021 67 2022 67 2023 67 Thereafter 276 Total $ 622 Contract Balances The Company did not record any contract assets as none of its right to payment was subject to something other than passage of time. The Company also did not record any contract liabilities as it recognizes revenue only at the amount to which it has the right to invoice for the electricity and RECs delivered; therefore, there are no advanced payments or billings in excess of electricity or RECs delivered.

Divested Operations

Divested Operations	12 Months Ended
	Dec. 31, 2018
Discontinued Operations and Disposal Groups [Abstract]
Divested Operations	Divested Operations Chilean Sale On May 21, 2018, the Company, through its indirect wholly-owned subsidiaries, entered into a stock purchase agreement with a third party pursuant to which the Company agreed to sell, and the buyer agreed to purchase, certain subsidiaries which hold approximately a 71% interest in El Arrayán Wind and assets and rights relating to ownership and operation of an extension of the trunk transmission system in Chile (Chilean Sale). El Arrayán Wind is a wind electric generation facility located approximately 400 kilometers north of Santiago on the coast of Chile in which the Company had an owned interest of approximately 81 megawatts (MW). On August 20, 2018, the Company completed the Chilean Sale for cash proceeds of $70 million . The Company measured impairment expense as the difference between the carrying amount of the net assets and fair value less estimated costs to sell. As a result, the Company recorded a total impairment expense of $7 million for the year ended December 31, 2018 in the consolidated statements of operations. The operating results of El Arrayán Wind were included on the consolidated statements of operations through the date of sale.

Acquisitions

Acquisitions	12 Months Ended
	Dec. 31, 2018
Business Combinations [Abstract]
Acquisitions	Acquisitions All acquisitions completed during 2018 and 2017 were in alignment with the Company's strategy to expand its portfolio of power generating projects. Stillwater Acquisition On November 20, 2018, a subsidiary of the Company acquired 100% of Stillwater Wind LLC, an 80 MW wind project located in Stillwater County, Montana, for a total consideration of $111 million , net of cash acquired, in addition to $1 million of capitalized transaction-related expenses. PSP Investments and Allianz Renewable Energy Partners of America, LLC, whom are noncontrolling interests, contributed $95 million of the total consideration. The fair value of the purchase consideration, including transaction-related expenses of the asset acquisition, is allocated to the relative fair value of the individual assets, operating contracts and liabilities assumed. No gain or loss was recognized upon acquisition. MSM Acquisition On August 10, 2018, the Company subscribed for (1) a 51% limited partnership interest in MSM LP Holdings LP, which holds 99.98% of the economic interests in MSM. MSM operates the approximately 143 MW wind project located in the Chaudière-Appalaches region south of Québec City, Canada, which achieved commercial operation in the first quarter of 2018. The Company also acquired (1) 70% of the issued and outstanding shares in the capital of Pattern MSM GP Holdings Inc. and (2) 70% of the issued and outstanding shares in the capital of Pattern Development MSM Management ULC from Pattern Energy Group LP for aggregate consideration of $31 million , net of cash acquired. MSM was determined to be a VIE, for which the Company is the primary beneficiary. The Company recorded the fair value of the individual assets, operating contracts and liabilities of the VIE, which did not meet the definition of a business. The noncontrolling interest was recorded at fair value estimated using the purchase price paid by PSP Investments pursuant to the purchase and sale agreement. No gain or loss was recognized upon acquisition. The Company incurred transaction-related expenses of $1 million which were recorded in net earnings (loss) on transactions in the consolidated statements of operations for the year ended December 31, 2018. Japan Acquisitions On March 7, 2018, the Company acquired (1) Tsugaru Holdings, which owns a 122 MW wind project company located in Aomori Prefecture, Japan that is expected to commence commercial operations in early to mid-2020; (2) Ohorayama, a 33 MW wind project company located in Kochi Prefecture, Japan that commenced commercial operations in March 2018; (3) Kanagi, a 10 MW solar project company located in Shimane Prefecture, Japan that commenced commercial operations in 2006; (4) Otsuki, a 12 MW wind project company located in Kochi Prefecture, Japan that commenced commercial operations in 2006; and (5) Futtsu, a 29 MW solar project company located in Chiba Prefecture, Japan that commenced commercial operations in 2016 (collectively referred to as the Japan Acquisition) for total consideration of $264 million , net of cash acquired, of which $106 million is a contingent payment. As part of the acquisition, the Company also assumed $181 million of debt. The Company incurred transaction related expenses of $1 million which were recorded in net earnings (loss) on transactions in the consolidated statements of operations for the year ended December 31, 2018. Contingent purchase consideration with a fair value of $103 million , subject to foreign currency exchange rate changes, is contingent upon term conversion of the Tsugaru construction loan or the commencement of commercial operations of Tsugaru. Both the term loan conversion and commencement of commercial operations are expected to occur in 2020. U pon the term conversion of the Ohorayama construction loan in June 2018, the Company was obligated to make a $3 million payment, subject to foreign currency exchange rate changes, to Pattern Energy Group LP. The Company paid this consideration in July 2018 . See Note 14 , Fair Value Measurement for further discussion on the fair value of the contingent consideration. The Company recorded the fair value of the individual assets, operating contracts and assumed liabilities of the Japan acquisition. The noncontrolling interest was recorded at fair value estimated using a projected cash flow stream of distributable cash, discounted to present value with a discount rate reflecting the cost of equity adjusted for control premium. Deferred tax liabilities were established as part of acquisition accounting due to temporary tax to book basis differences as a result of the step up in fair value related to property, plant and equipment, which established goodwill for $60 million . The valuation of certain assets and liabilities in the Japan Acquisition is final as of December 31, 2018. The Japan Acquisition provides the Company with an established presence in Japan to support future growth plans and provides diversification which is of benefit to the risk profile of the Company's overall operating project portfolio. As a result of the Japan Acquisition, for the year ended December 31, 2018 , property, plant and equipment, net, increased by $7 million , construction in progress decreased by $3 million , other assumed liabilities increased by $6 million and deferred tax liabilities decreased by $2 million from the preliminary purchase price allocation primarily related to a change in the estimated cost of asset retirement obligations and deferred tax liabilities. Broadview Acquisition On April 21, 2017, the Company completed the acquisition of (1) a 99% ownership interest in Western Interconnect, a 35 -mile 345 kV transmission line; and (2) a 100% ownership interest in Broadview Project which indirectly owns 100% of the Class B membership interest in Broadview Energy Holdings LLC (Broadview Holdings), which consists of the 324 MW Broadview wind power projects, for total consideration of $190 million , net of cash acquired and a post-closing payment of approximately $21 million contingent upon the commercial operation of the Grady Project. The Grady Wind Energy Center, LLC (the Grady Project) is a wind power project on the Identified ROFO Projects list being developed by Pattern Development. The identifiable assets, operating contracts and liabilities assumed for the Broadview Project were recorded at their fair values, which corresponded to the sum of the cash purchase price, contingent consideration payment, and the fair value of the other investors' noncontrolling interests. Meikle Acquisition On August 10, 2017, the Company acquired (1) a 50.99% limited partnership interest in Meikle, a 179 MW wind project company located in the Peace River Regional District of British Columbia, Canada, which achieved commercial operations in the first quarter of 2017; and (2) 70% of the issued and outstanding shares of Meikle Wind Energy Corp. for a total consideration of $58 million , net of cash acquired, in addition to $1 million of capitalized transaction-related expenses. The fair value of the purchase consideration, including transaction-related expenses of the asset acquisition, and fair value of the noncontrolling interest was allocated to the relative fair value of the individual assets, operating contracts and liabilities assumed. The noncontrolling interest was recorded at fair value estimated using the purchase price paid by the affiliate of PSP Investments pursuant to the purchase and sale agreement. The aggregate purchase prices of the acquisitions were allocated as follows (in millions): December 31, 2018 2017 Japan Acquisition (1) MSM (2) Stillwater (2) Broadview (1) Meikle (2) Purchase price Cash paid for acquisitions, net of cash and restricted cash acquired $ 158 $ 31 $ 111 $ 169 $ 58 Contingent consideration 106 — — 21 — $ 264 $ 31 $ 111 $ 190 $ 58 Allocation Property, plant and equipment, net $ 269 $ 270 $ 120 $ 628 $ 376 Construction in progress 179 — — — — Intangibles 103 — — 22 29 Goodwill 60 — — — — Other assets acquired 20 38 4 12 8 Debt (181 ) (196 ) — (51 ) (266 ) Deferred tax liabilities (65 ) — — — — Advanced lease revenue — (29 ) — — — Other liabilities assumed (110 ) (14 ) (13 ) (95 ) (24 ) Assets and liabilities assumed before noncontrolling interests 275 69 111 516 123 Less: noncontrolling interests (11 ) (38 ) — (326 ) (65 ) Total consideration allocated to acquired assets and liabilities $ 264 $ 31 $ 111 $ 190 $ 58 1) Business Combination 2) Asset Acquisition Supplemental pro forma data (unaudited) Ohorayama commenced operations in March 2018 and until approximately one week before the Company's acquisition, Ohorayama was still under construction. In addition, Tsugaru is expected to commence commercial operations in early to mid-2020. Therefore, pro forma data for Ohorayama and Tsugaru have not been provided as there is no material difference between pro forma data that give effects to the Japan Acquisitions as if it had occurred on January 1, 2017 and the actual data reported for the years ended December 31, 2018 and 2017. Broadview reached commercial operations in March 2017 and until approximately three weeks before acquisition, Broadview was still under construction. Therefore, pro forma data for Broadview has not been provided as there is no material difference between pro forma data that give effect to the Broadview Project acquisition as if it had occurred on January 1, 2016 and actual data reported for the years ended December 31, 2017 and 2016. The unaudited pro forma statement of operations data below gives effect to the acquisition of Kanagi, Otsuki and Futtsu as if they had occurred on January 1, 2017. The pro forma net loss for the year ended December 31, 2018 was adjusted to exclude nonrecurring transaction related expenses of $1 million . The unaudited pro forma data is presented for illustrative purposes only and is not intended to be indicative of actual results that would have been achieved had these acquisitions been consummated as of January 1, 2017. The unaudited pro forma data should not be considered representative of the Company’s future financial condition or results of operations. Year ended December 31, Unaudited pro forma data (in millions) 2018 2017 Pro forma total revenue $ 487 $ 435 Pro forma total expenses 556 520 Pro forma net loss (69 ) (85 ) Less: pro forma net loss attributable to noncontrolling interest (211 ) (65 ) Pro forma net income (loss) attributable to Pattern Energy $ 142 $ (20 ) The following table presents the amounts included in the consolidated statements of operations for the business combinations discussed above since their respective dates of acquisition: Year ended December 31, Unaudited data (in millions) 2018 2017 Total revenue $ 96 $ 33 Total expenses 105 50 Net loss (9 ) (17 ) Less: net loss attributable to noncontrolling interest (48 ) (17 ) Net income attributable to Pattern Energy $ 39 $ —

Intangible Assets and Liabiliti

Intangible Assets and Liabilities and Goodwill	12 Months Ended
	Dec. 31, 2018
Goodwill and Intangible Assets Disclosure [Abstract]
Intangible Assets and Liability and Goodwill	Intangible Assets and Liabilities and Goodwill The following presents the major components of the long-lived intangible assets and liabilities (in millions): December 31, 2018 Weighted Average Remaining Life Gross Accumulated Amortization Net Intangible assets Power purchase agreement 15 $ 225 $ (31 ) $ 194 Industrial revenue bond tax savings 23 13 (1 ) 12 Other intangible assets 33 14 (1 ) 13 Total intangible assets $ 252 $ (33 ) $ 219 Intangible liabilities Power purchase agreement 14 60 (13 ) 47 Leasehold interest 22 9 — 9 Total intangible liabilities $ 69 $ (13 ) $ 56 December 31, 2017 Weighted Average Remaining Life Gross Accumulated Amortization Net Intangible assets Power purchase agreement 15 $ 127 $ (18 ) $ 109 Industrial revenue bond tax savings 24 13 — 13 Other intangible assets 34 15 (1 ) 14 Total intangible assets $ 155 $ (19 ) $ 136 Intangible liability Power purchase agreement 15 $ 60 $ (9 ) $ 51 Amortization of the PPA asset and PPA liability is reflected in electricity sales in the consolidated statements of operations, which resulted in net reduction of approximately $9 million , $4 million and $3 million in electricity sales for the years ended December 31, 2018 , 2017 and 2016 , respectively. For the years ended December 31, 2018 , 2017 and 2016 , the Company recorded amortization expense of less than $1 million related to other intangible assets in depreciation, amortization and accretion in the consolidated statements of operations. As a result of the Japan Acquisition, the Company recorded a $103 million intangible PPA asset resulting from market prices that are lower than the contractual prices. In addition, the Company recorded a $9 million intangible leasehold interest liability, as a result of higher market prices compared to the contractual prices. As part of the 2017 Broadview acquisition, the Company acquired an intangible asset related to future property tax savings resulting from the issuance of industrial revenue bonds during construction of the project. The following table presents estimated future amortization for the next five years related to intangible assets and liabilities. The sum of estimated future amortization in the following table may differ from intangible assets and liabilities balances due to rounding. Year ended December 31, Power Purchase Agreements, Net Industrial revenue bond tax savings Other Intangible Assets Leasehold Interest 2019 $ 10 $ 1 $ 1 $ — 2020 10 1 1 — 2021 10 1 1 — 2022 10 1 1 — 2023 10 1 1 — Thereafter 101 9 10 (7 ) Goodwill In connection with the Japan Acquisition, the Company recognized goodwill of approximately $60 million , which was allocated to the operating business reporting segment. The following table presents a reconciliation of the beginning and ending carrying amounts of goodwill (in millions): Total Balances at December 31, 2017 $ — Net additions during the period 60 Foreign currency translation adjustment (2 ) Balances at December 31, 2018 $ 58

Property, Plant and Equipment

Property, Plant and Equipment	12 Months Ended
	Dec. 31, 2018
Property, Plant and Equipment [Abstract]
Property, Plant and Equipment	Property, Plant and Equipment The following presents the categories within property, plant and equipment (in millions): December 31, 2018 2017 Operating wind farms $ 4,972 $ 4,641 Transmission line 94 94 Furniture, fixtures and equipment 16 12 Subtotal 5,082 4,747 Less: accumulated depreciation (963 ) (782 ) Property, plant and equipment, net $ 4,119 $ 3,965 The Company recorded depreciation expense related to property, plant and equipment of $245 million , $195 million and $172 million for the years ended December 31, 2018 , 2017 and 2016 , respectively.

Variable Interest Entities (Not

Variable Interest Entities (Notes)	12 Months Ended
	Dec. 31, 2018
Variable Interest Entities [Abstract]
Variable Interest Entities	Variable Interest Entities The Company consolidates VIEs in which it holds a variable interest and is the primary beneficiary. The Company has determined that Logan's Gap, Panhandle 1, Panhandle 2, Post Rock, Amazon Wind, Broadview Energy Holdings LLC (a subsidiary of Broadview Project), MSM, and Stillwater New Energy Holdings LLC are VIEs and as the managing member of the respective partnerships, it is the primary beneficiary by reference to the power and benefits criterion under ASC 810, Consolidation . The Company considered responsibilities within the contractual agreements, which grant it the power to direct the activities of the VIE that most significantly impact the VIE's economic performance. Such activities include management of the wind farms' operations and maintenance, budgeting, and establishing policies and procedures. In addition, the Company has the obligation to absorb losses or the right to receive benefits that could potentially be significant to the VIEs on the basis of the income allocations and cash distributions. The Company’s equity method investment in Pattern Development is considered to be a VIE primarily because the total equity at risk is not sufficient to permit Pattern Development to finance its activities without additional subordinated financial support by the equity holders. The Company does not hold the power or benefits to be the primary beneficiary and does not consolidate the VIE. The carrying value of its unconsolidated investment in Pattern Development was $144 million as of December 31, 2018 . The Company's maximum exposure to loss is equal to the carrying value of its investment in Pattern Development. The following table summarizes the carrying amounts of major consolidated balance sheet items for consolidated VIEs as of December 31, 2018 and 2017 (in millions). All assets (excluding deferred financing costs, net and long-lived intangible assets, net) and liabilities included in the consolidated VIE presented below are (1) assets that can be used only to settle obligations of the VIE or (2) liabilities for which creditors do not have recourse to the general credit of the primary beneficiary. December 31, 2018 2017 Assets Current assets: Cash and cash equivalents $ 36 $ 33 Restricted cash 4 4 Trade receivables 13 13 Prepaid expenses 6 5 Other current assets 2 3 Total current assets 61 58 Restricted cash 3 3 Construction in progress 1 — Property, plant and equipment, net 2,156 1,985 Deferred financing costs, net 2 2 Intangible assets, net 12 12 Other assets 12 13 Total assets $ 2,247 $ 2,073 Liabilities Current liabilities: Accounts payable and other accrued liabilities $ 27 $ 27 Accrued construction costs 1 1 Current portion of long-term debt, net 4 — Other current liabilities 5 5 Total current liabilities 37 33 Long-term debt, net 149 — Intangible liability, net 48 51 Asset retirement obligations 57 22 Other long-term liabilities 36 25 Deferred revenue 26 — Total liabilities $ 353 $ 131

Unconsolidated Investments

Unconsolidated Investments	12 Months Ended
	Dec. 31, 2018
Equity Method Investments and Joint Ventures [Abstract]
Unconsolidated Investments	Unconsolidated Investments The Company's unconsolidated investments consist of the following for the periods presented below (in millions): December 31, Percentage of Ownership December 31, 2018 2017 2018 2017 South Kent $ 5 $ 6 50.0 % 50.0 % Grand 5 7 45.0 % 45.0 % K2 — 103 — % 33.3 % Armow 116 133 50.0 % 50.0 % Pattern Development 144 62 29.3 % 20.9 % Unconsolidated investments $ 270 $ 311 K2 On November 6, 2018, the Company, through its indirect wholly-owned subsidiary, entered into a PSA for the sale of its minority interest in the K2 project. The Company had an owned interest of approximately 90 MW. On December 31, 2018, the Company completed the sale of the K2 project for cash proceeds of approximately $158 million and recorded a gain on sale of approximately $71 million , which is included in net earnings (loss) on transactions in the statements of operations for the year ended December 31, 2018. South Kent The Company is a noncontrolling investor in a joint venture established to develop, construct, and own a wind power project located in Ontario, Canada. The project has a 20 -year PPA, and commenced commercial operation in March 2014. Grand The Company is a noncontrolling investor in a joint venture established to develop, construct, and own a wind power project located in Ontario, Canada. The project has a 20 -year PPA and commenced commercial operation in December 2014. Armow The Company is a noncontrolling investor in a joint venture established to develop, construct, and own a wind power project located in Ontario, Canada. The project has a 20 -year PPA, and commenced commercial operation in December 2015. Pattern Development Under the Second Amended and Restated Agreement of Limited Partnership of Pattern Development, the Company has the right to contribute up to $300 million to Pattern Development in order to secure and retain up to a 29% ownership interest in the partnership. On July 27, 2017, the Company funded an initial $60 million capital call. As of December 31, 2018 , the Company has funded approximately $183 million in aggregate and holds an approximately 29% ownership interest in Pattern Development. The Company is a noncontrolling investor in Pattern Development, but has significant influence over Pattern Development. Accordingly, the investment is accounted for under the equity method of accounting. The Company capitalized approximately $2 million of transaction costs for the year ended December 31, 2017 . The Company's initial investment in Pattern Development of $60 million was approximately $41 million higher than the Company's underlying equity in the net assets of Pattern Development at the time of the initial funding. This equity method basis difference was primarily attributable to equity method goodwill. Basis Amortization of Unconsolidated Investments The cost basis of the net assets of the investment may be different than the Company's proportional interest in the equity of the investee. On the acquisition date, the Company determines the fair value of the identifiable assets and assumed liabilities in accordance with ASC 805, Business Combinations . The resulting fair values are compared with the assets and liabilities recorded in the investee's financial statements, and the resulting difference is basis difference. Basis differences for the Company's investments were primarily attributable to property, plant and equipment, PPAs, and equity method goodwill. The Company amortizes the basis difference attributable to property, plant and equipment, and PPAs over their useful life and contractual life, respectively. The Company does not amortize equity method goodwill. For the years ended December 31, 2018 , 2017 and 2016 , the Company recorded basis difference amortization for its unconsolidated investments of approximately $11 million , $11 million and $6 million , respectively, in earnings in unconsolidated investments, net on the consolidated statements of operations.

Debt

Debt	12 Months Ended
	Dec. 31, 2018
Debt Disclosure [Abstract]
Debt	Debt The Company’s debt consists of the following for periods presented below (in millions): December 31, 2018 December 31, Contractual Interest Rate Effective Interest Rate 2018 2017 Maturity Corporate-level Corporate Revolving Credit Facility $ 198 $ — varies (1 ) 4.01 % November 2022 2020 Notes 225 225 4.00 % 6.60 % July 2020 2024 Notes 350 350 5.88 % 5.88 % February 2024 Project-level Fixed interest rate El Arrayán EKF term loan (6) — 99 — % — % N/A Santa Isabel term loan 100 104 4.57 % 4.57 % September 2033 Mont Sainte Marguerite-Med Term Loan 62 — 3.97 % 3.97 % December 2029 Mont Sainte Marguerite-Long Term loan 93 — 5.04 % 5.04 % June 2042 Variable interest rate Japan Credit Facility 25 — varies (5 ) 1.82 % August 2022 Ocotillo commercial term loan 281 289 4.30 % 4.01 % (3 ) June 2033 El Arrayán commercial term loan (6) — 90 — % — % N/A Spring Valley term loan (6) — 126 — % — % N/A St. Joseph term loan (2) 152 172 4.06 % 4.11 % (3 ) November 2033 Western Interconnect term loan (7) 52 54 4.19 % 4.21 % (3 ) May 2034 Meikle term loan (2) 239 267 3.81 % 3.97 % (3 ) May 2024 Futtsu term loan 75 — 1.07 % 1.85 % (3 ) December 2033 Ohorayama term loan 93 — 0.87 % 0.88 % (3 ) February 2036 Tsugaru Construction Loan 131 — 0.72 % 0.72 % (3 ) March 2038 Tsugaru Holdings Loan Agreement 59 — 3.07 % 3.07 % July 2022 Imputed interest rate Hatchet Ridge financing lease obligation 180 192 1.43 % 1.43 % December 2032 2,315 1,968 Unamortized premium/discount, net (4) (11 ) (14 ) Unamortized financing costs (21 ) (23 ) Total debt, net $ 2,283 $ 1,931 As reflected on the consolidated balance sheets Revolving credit facility, current $ 198 $ — Revolving credit facility 25 — Current portion of long-term debt, net of financing costs 56 52 Long term debt, net of financing costs 2,004 1,879 Total debt, net $ 2,283 $ 1,931 (1) Refer to Corporate Revolving Credit Facility for interest rate details. (2) The amortization for the St. Joseph term loan and the Meikle term loan are through September 2036 and December 2038, respectively, which differs from the stated maturity date of such loans due to prepayment requirements. (3) Includes impact of interest rate swaps. See Note 12 , Derivative Instruments , for discussion of interest rate swaps. (4) The discount relates to the 2020 Notes and MSM term loans. (5) Refer to Japan Credit Facility for interest rate details. (6) The El Arrayán EKF term loan and El Arrayán commercial term loan were included as part of the Chilean Sale on August 20, 2018. The Spring Valley term loan was prepaid in full on December 31, 2018. (7) Refer to "Project Debt - Western Interconnect" below for additional borrowing details. The following are principal payments, excluding deferred financing costs, due under the Company's debt as of December 31, 2018 for the following years (in millions): Amount 2019 $ 254 2020 288 2021 74 2022 154 2023 73 Thereafter 1,472 Total $ 2,315 Interest and commitment fees incurred and interest expense for debt consisted of the following (in millions): Year ended December 31, 2018 2017 2016 Corporate-level interest and commitment fees incurred $ 38 $ 34 $ 18 Project-level interest and commitment fees incurred 64 55 48 Capitalized interest, commitment fees, and letter of credit fees (4 ) — — Amortization of debt discount/premium, net 5 5 4 Amortization of financing costs 6 8 7 Other interest — — 1 Interest expense $ 109 $ 102 $ 78 Corporate Level Debt Corporate Revolving Credit Facility On November 21, 2017, certain of our subsidiaries entered into a Second Amended and Restated Credit and Guaranty Agreement (the Revolving Credit Facility). The Revolving Credit Facility provides for a revolving credit facility of $440 million , decreased from the previous limit of $500 million . The facility has a five -year term and is comprised of a revolving loan facility, a letter of credit facility and a swingline facility. The facility is secured by pledges of the capital stock and ownership interests in certain of our holding company subsidiaries, in addition to other customary collateral. As of December 31, 2018 , $197 million was available for borrowing under the $440 million Revolving Credit Facility. The Revolving Credit Facility contains a broad range of covenants that, subject to certain exceptions, restrict the Company’s holding company subsidiaries' ability to incur debt, grant liens, sell or lease assets, transfer equity interests, dissolve, pay distributions and change its business. As of December 31, 2018 , the Company's holding company subsidiaries are in compliance with covenants contained in the Revolving Credit Facility. The loans under the Revolving Credit Facility are base rate loans, Eurodollar rate loans, Canadian prime rate loans or CDOR rate loans. The base rate loans accrue interest at the fluctuating rate per annum equal to the greatest of the (i) the U.S. dollar prime rate, (ii) the federal funds rate plus 0.50% and (iii) LIBOR one month plus 1.0% , plus an applicable margin ranging from 0.625% to 0.875% (corresponding to applicable leverage ratios of the borrowers). The Eurodollar rate loans accrue interest at a rate per annum equal to LIBOR, as published by Reuters plus an applicable margin ranging from 1.625% to 1.875% (corresponding to applicable leverage ratios of the borrowers). The Canadian prime rate loans accrue interest at a fluctuating rate per annum equal to the greater of (i) the Canadian dollar prime rate and (ii) the average CDOR rate for a 30 day term plus 0.50% , plus an applicable margin ranging from 0.625% to 0.875% (corresponding to applicable leverage ratios of the borrowers). The CDOR rate loans accrue interest at a rate per annum equal to CDOR, as published by Reuters plus an applicable margin ranging from 1.625% to 1.875% (corresponding to applicable leverage ratios of the borrowers). Under the facility, the Company pays a revolving commitment fee equal to a percentage per annum determined by reference to the leverage ratio of the borrowers, ranging from 0.30% to 0.50% . Letter of credit fees are also paid. As of December 31, 2018 and 2017 , letters of credit of $45 million and $48 million , respectively, were available to be issued under the Revolving Credit Facility. 2020 Notes In July 2015, the Company issued $225 million aggregate principal amount of 4.00% convertible senior notes due 2020 (2020 Notes). The 2020 Notes bear interest at a rate of 4.00% per year, payable semiannually in arrears on January 15 and July 15 of each year, beginning on January 15, 2016. The 2020 Notes will mature on July 15, 2020. The 2020 Notes were sold in a private placement. Upon conversion, the Company may, at its discretion, pay cash, shares of the Company’s Class A common stock, or a combination of cash and stock. The 2020 Notes were set at an initial conversation rate of 35.4925 shares of Class A common stock per $1,000 principal amount of 2020 Notes, which is equivalent to an initial conversion price of approximately $28.175 per share of Class A common stock. The conversion rate is subject to adjustment in some events (including, but not limited to, certain cash dividends made to holders of the Company's Class A common stock which exceed the initial dividend threshold of $0.363 per quarter per share). The conversion rate would be adjusted to offset the effect of the portion of the dividend in excess of $0.363 , provided that the adjustment would result a change of at least 1% in the then effective conversion rate. During the year ended December 31, 2017, the conversion rate increased to 35.8997 shares of Class A common stock per $1,000 principal amount of 2020 Notes. The conversion rate will not be adjusted for any accrued and unpaid interest. The 2020 Notes are not redeemable prior to maturity. The 2020 Notes are guaranteed on a senior unsecured basis by a subsidiary of the Company and are general unsecured obligations of the Company. The obligations rank senior in rights of payment to the Company’s subordinated debt, equal in right of payment to the Company’s unsubordinated debt and effectively junior in right of payment to any of the Company’s secured indebtedness to the extent of the value of the assets securing such indebtedness. The following table presents a summary of the equity and liability components of the 2020 Notes (in millions): December 31, 2018 2017 Principal $ 225 $ 225 Less: Unamortized debt discount (8 ) (13 ) Unamortized financing costs (2 ) (3 ) Carrying value of convertible senior notes $ 215 $ 209 Carrying value of the equity component (1) $ 24 $ 24 (1) Included in the consolidated balance sheets as additional paid-in capital, net of $1 million in equity issuance costs. Project Debt The Company typically finances its wind projects through project entity specific debt secured by each project's assets with no recourse to the Company. Typically, these financing arrangements provide for a construction loan, which upon completion may be converted into a term loan or repaid through capital contributions from the Company and tax equity investors. Collateral for project level facilities typically include each project's tangible assets and contractual rights and cash on deposit with the depository agents. Each loan agreement contains a broad range of covenants that, subject to certain exceptions, restrict each project's ability to incur debt, grant liens, sell or lease certain assets, transfer equity interests, dissolve, make distributions and change their business. As of December 31, 2018 , all projects were in compliance with their financing covenants. Western Interconnect In December 2018, the Company refinanced Western Interconnect project's term loan of $ 52 million along with an associated letter of credit of $4 million and entered into a new term loan with a total loan capacity of $ 90 million expected to mature in May 2034 with an associated letter of credit of $ 5 million . The incremental borrowing of $38 million is anticipated to occur during the second quarter of 2019. The refinancing was treated as an extinguishment of debt for which the Company recognized a loss on extinguishment of debt of $2 million in other income (expense), net on the consolidated statements of operations for the year ended December 31, 2018. The $2 million loss on extinguishment includes $1 million paid to existing lenders. Spring Valley In December 2018, the Company prepaid 100% of the outstanding balance of the Spring Valley project's term loan of $119 million . A $4 million loss on the debt extinguishment was recorded in other income (expense), net in the consolidated statements of operations, primarily due to expensing previously recorded amounts in deferred financing costs. As a result of the early extinguishment of debt, the Company lost its cash flow hedge accounting treatment on the related interest rate swaps. See Note 12 , Derivative Instruments , for additional information. Japan Credit Facility In August 2018, GPG entered into a credit agreement for a revolving credit facility (the Japan Credit Facility). Under the Japan Credit Facility, GPG may borrow up to $32 million and the Japan Credit Facility matures in August 2022. The base rate is based on the Japan Credit Facility Tokyo Interbank Offered Rate (TIBOR) plus an applicable margin between 1.75% and 2.25% plus an annual commitment fee of 0.30% . As of December 31, 2018 , $7 million was available for borrowing. Tsugaru Facility In March 2018, Tsugaru entered into a credit agreement for a construction facility (Tsugaru Construction Loan), a term facility, a letter of credit facility (the LC Facility) and a Japanese consumption tax facility (the JCT Facility) (collectively, the Tsugaru Facility). Under the Tsugaru Facility, up to $371 million may be borrowed to fund the construction of Tsugaru which automatically converts to a term facility upon the earlier of completion of construction of the project (expected to be March 2020) or September 2020 (the Term Conversion Date). The Tsugaru Construction Loan, including the term facility and LC Facility, mature 18 years following the Term Conversion Date, not later than March 2039. The interest rate on the Tsugaru Construction Loan and term facility is TIBOR plus 0.65% . The LC Facility establishes a $20 million debt service reserve account letter of credit and an $8 million operations and maintenance reserve account letter of credit with amounts outstanding under the letters of credit owing interest at a rate of 1.10% and fees on the undrawn amounts of 0.30% . The JCT Facility provides for up to $34 million to pay Japanese consumption taxes arising from payment of project costs, with an interest rate of TIBOR plus 0.30% and a maturity date corresponding to the Term Conversion Date. A commitment fee of 0.3% is owed on any available amounts under the Construction Facility and the JCT Facility and on any undrawn amounts on the letters of credit up to the Term Conversion Date. Collateral for the credit facility includes Tsugaru's tangible assets and contractual rights and cash on deposit with the depository agent. The credit agreement contains a broad range of covenants that, subject to certain exceptions, restrict Tsugaru's ability to incur debt, grant liens, sell or lease certain assets, transfer equity interests, dissolve, make distributions or change its business. As of December 31, 2018 , outstanding borrowings under the Tsugaru Construction Loan totaled $ 131 million . Tsugaru Holdings Loan Agreement In March 2018, Tsugaru Holdings entered into a loan agreement (Tsugaru Holdings Loan Agreement) that provides for borrowings of up to $70 million during the Tsugaru construction period, until no later than September 2020. The interest rate on outstanding borrowings under the Tsugaru Holdings Loan Agreement is TIBOR plus 3.0% with principal due July 2022 and a commitment fee of 0.50% on the unused portion of the Tsugaru Holdings Loan Agreement. The Tsugaru Holdings Loan Agreement is subject to certain covenants and is secured by the membership interests and other rights. As of December 31, 2018 , outstanding borrowings under the Tsugaru Holdings Loan Agreement totaled $ 59 million . Financing Lease Obligations In December 2010, Hatchet Ridge entered into a sale-leaseback agreement to finance the project facility for 22 years . The Company evaluated the agreement in accordance with ASC 840 and ASC 360, Property Plant and Equipment, and determined that due to continuing involvement with the project facility, the Company is precluded from treating the agreement as a sale-lease back transaction and accounts for the agreement as a financing lease obligation. Collateral for the agreement includes Hatchet Ridge’s tangible assets and contractual rights and cash on deposit with the depository agent. Its loan agreement contains a broad range of covenants that, subject to certain exceptions, restrict Hatchet Ridge’s ability to incur debt, grant liens, sell or lease assets, transfer equity interests, dissolve, pay distributions and change its business. Payments under the financing lease for the years ended December 31, 2018 , 2017 and 2016 , were $15 million , $13 million and $15 million , respectively.

Asset Retirement Obligation

Asset Retirement Obligation	12 Months Ended
	Dec. 31, 2018
Asset Retirement Obligation Disclosure [Abstract]
Asset Retirement Obligations	Asset Retirement Obligations The Company’s asset retirement obligations represent the estimated cost of decommissioning the turbines, removing above-ground installations and restoring sites at the end of their estimated economic useful life. In the third quarter of 2018, the Company committed to a plan to re-power its Gulf Wind project by the end of 2020. In connection with the decision to repower the facility and accelerate decommissioning of the existing facilities, the Company received updated cost information. This initiated a new decommissioning cost study for which the Company revised its estimated future cash flows to reflect the updated costs and timing for its asset retirement obligations. The Company recognized the revision by increasing the carrying amount of the liability for the asset retirement obligation and the carrying amount of the related property, plant and equipment. The change in estimate did not result in any charge to net income (loss) for the year ended December 31, 2018. The following table presents a reconciliation of the beginning and ending aggregate carrying amounts of asset retirement obligations (in millions): December 31, 2018 2017 Beginning asset retirement obligations $ 57 $ 45 Net additions during the year (1) 67 9 Foreign currency translation adjustment (2 ) — Divested operations (3 ) — Revision in estimated cash flows 85 — Accretion expense 5 3 Ending asset retirement obligations $ 209 $ 57 (1) Reflects non-cash additions due to acquisitions and construction during the year ended December 31, 2018. See Note 5 , Acquisitions , for discussion of acquisitions.

Derivative Instruments

Derivative Instruments	12 Months Ended
	Dec. 31, 2018
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivative Instruments	Derivative Instruments The Company employs a variety of derivative instruments to manage its exposure to fluctuations in electricity prices, interest rates and foreign currency exchange rates. Energy prices are subject to swings as supply and demand are impacted by, among many other unpredictable items, weather, market liquidity, generating facility availability, customer usage, storage, and transmission and transportation constraints. Interest rate risk exists primarily on variable-rate debt for which the cash flows vary based upon movement in interest rates. Additionally, the Company is exposed to foreign currency exchange rate risk primarily from its business operations in Canada and Japan. The Company’s objectives for holding these derivative instruments include reducing, eliminating and efficiently managing the economic impact of these exposures as effectively as possible. The Company does not hedge all of its electricity price risk, interest rate risks, and foreign currency exchange rate risks, thereby exposing the unhedged portions to changes in market prices. As of December 31, 2018 , the Company had other energy-related contracts that did not meet the definition of a derivative instrument or qualified for the NPNS exception and were therefore exempt from fair value accounting treatment. The following tables present the fair values of the Company's derivative instruments on a gross basis as reflected on the Company’s consolidated balance sheets (in millions): December 31, 2018 Derivative Assets Derivative Liabilities Current Long-Term Current Long-Term Fair Value of Designated Derivatives: Interest rate swaps $ — $ 3 $ 2 $ 25 Fair Value of Undesignated Derivatives: Interest rate swaps — — — 4 Energy derivative 7 — — — Foreign currency forward contracts 6 6 — 2 Congestion revenue rights 1 — — — Total Fair Value $ 14 $ 9 $ 2 $ 31 December 31, 2017 Derivative Assets Derivative Liabilities Current Long-Term Current Long-Term Fair Value of Designated Derivatives: Interest rate swaps $ — $ 2 $ 4 $ 18 Fair Value of Undesignated Derivatives: Interest rate swaps — — 1 3 Energy derivative 19 8 — — Foreign currency forward contracts — — 3 — Total Fair Value $ 19 $ 10 $ 8 $ 21 The following table summarizes the notional amounts of the Company's outstanding derivative instruments (in millions except for MWh): December 31, Unit of Measure 2018 2017 Designated Derivative Instruments Interest rate swaps USD $ 319 $ 253 Interest rate swaps CAD $ 721 $ 736 Interest rate swaps JPY ¥ 55,675 ¥ — Undesignated Derivative Instruments Interest rate swaps USD $ 138 $ 85 Energy derivative MWh 193,252 697,471 Foreign currency forward contracts CAD $ 106 $ 128 Foreign currency forward contracts JPY ¥ 11,589 ¥ — Congestion revenue rights MWh 505 — Derivatives Designated as Hedging Instruments Cash Flow Hedges The Company has interest rate swap agreements to hedge variable rate project-level debt. Under these interest rate swaps, the projects make fixed-rate interest payments and the counterparties to the agreements make variable-rate interest payments. For interest swaps that are designated and qualify as cash flow hedges, the effective portion of the gain or loss on the hedge is reported as a component of accumulated other comprehensive loss and reclassified into earnings in the period or periods during which a cash settlement occurs. The designated interest rate swaps have remaining maturities ranging from approximately 5.0 years to 24.3 years . The following table presents the pre-tax effect of the hedging instruments designated as cash flow recognized in accumulated other comprehensive loss, amounts reclassified to earnings for the following periods, as well as, amounts recognized in interest expense (in millions): Year ended December 31, Description 2018 2017 2016 Losses recognized in accumulated OCI Effective portion of change in fair value $ (6 ) $ (2 ) $ (8 ) Losses reclassified from accumulated OCI into: Interest expense Derivative settlements $ (5 ) $ (10 ) $ (8 ) Loss on derivatives De-designation of derivatives $ — $ (2 ) $ — The Company estimates that $1 million in accumulated other comprehensive loss will be reclassified into earnings over the next twelve months. Derivatives Not Designated as Hedging Instruments The following table presents gains and losses on derivatives not designated as hedges (in millions): Year ended December 31, Derivative Type Financial Statement Line Item 2018 2017 2016 Interest rate derivatives Gain (loss) on derivatives $ — $ (1 ) $ (2 ) Energy derivative Electricity sales $ (3 ) $ 5 $ (1 ) Foreign currency forward contracts Gain (loss) on derivatives $ 16 $ (7 ) $ (1 ) Foreign currency option contract Gain (loss) on derivatives $ 1 $ — $ — Interest Rate Derivatives The Company has interest rate swap agreements to hedge variable rate project-level debt. Under these interest rate swaps, the projects make fixed-rate interest payments and the counterparties to the agreements make variable-rate interest payments. For interest rate swaps that are not designated and do not qualify as cash flow hedges, the changes in fair value are recorded in loss on derivatives in the consolidated statements of operations as these hedges are not accounted for under hedge accounting. All of the Company's undesignated interest rate swaps have a remaining maturity of 11.5 years . Energy Derivative In 2010, Gulf Wind acquired an energy derivative instrument to manage its exposure to variable electricity prices over the life of the arrangement. The energy price swap fixes the price for a predetermined volume of production (the notional volume) over the life of the swap contract, through April 2019 , by locking in a fixed price per MWh. The notional volume agreed to by the parties is approximately 504,220 MWh per year. The energy derivative instrument does not meet the criteria required to adopt hedge accounting. As a result, changes in fair value are recorded in electricity sales in the consolidated statements of operations. As a result of the counterparty's credit rating downgrade, the Company received collateral related to the energy derivative agreement. The Company does not have the right to pledge, invest, or use the collateral for general corporate purposes. As of December 31, 2018 , the Company has recorded a current asset of $6 million to counterparty collateral and a current liability of $6 million to counterparty collateral liability representing the collateral received and corresponding obligation to return the collateral, respectively. Foreign Currency Forward and Option Contracts The Company has established a currency risk management program. The objective of the program is to mitigate the foreign exchange rate risk arising from transactions or cash flows that have a direct or underlying exposure in non-U.S. dollar denominated currencies in order to reduce volatility in the Company’s cash flow, which may have an adverse impact to the Company's short-term liquidity or financial condition. A majority of the Company’s power sale agreements and operating expenditures are transacted in U.S. dollars, with a growing portion transacted in currencies other than the U.S. dollar, primarily the Canadian dollar and Japanese yen. The Company enters into foreign currency forward and option contracts at various times to mitigate the currency exchange rate risk on Canadian dollar and, beginning in 2018, Japanese yen denominated cash flows. These instruments have remaining maturities ranging from three months to 11 years. The foreign currency forward and option contracts are considered non-designated derivative instruments and are not used for trading or speculative purposes. As a result, changes in fair value and settlements are recorded in gain (loss) on derivatives in the consolidated statements of operations. Congestion Revenue Rights Congestion revenue rights are financial instruments which were acquired via auction in the ERCOT power market that enable the Company to manage variability in electric energy congestion charges due to transmission grid limitations. The Company’s congestion revenue rights are considered non-designated derivative instruments and are not used for trading or speculative purposes. As a result, changes in fair value and settlements are recorded in gain (loss) on derivatives in the consolidated statements of operations.

Accumulated Other Comprehensive

Accumulated Other Comprehensive Loss	12 Months Ended
	Dec. 31, 2018
Equity [Abstract]
Accumulated Other Comprehensive Loss	Accumulated Other Comprehensive Loss The following table summarizes changes in the accumulated other comprehensive loss balance, net of tax, by component (in millions): Foreign Currency Effective Portion of Change in Fair Value of Derivatives Proportionate Share of Equity Investee's OCI Total Balances at December 31, 2015 $ (48 ) $ (14 ) $ (12 ) $ (74 ) Other comprehensive income (loss) before reclassifications 5 (7 ) 1 (1 ) Amounts reclassified from accumulated other comprehensive loss — 8 4 12 Net current period other comprehensive loss 5 1 5 11 Balances at December 31, 2016 (43 ) (13 ) (7 ) (63 ) Other comprehensive income (loss) before reclassifications 15 (3 ) 6 18 Amounts reclassified from accumulated other comprehensive loss — 11 8 19 Net current period other comprehensive loss 15 8 14 37 Balances at December 31, 2017 (28 ) (5 ) 7 (26 ) Other comprehensive loss before reclassifications (37 ) (4 ) (3 ) (44 ) Amounts reclassified from accumulated other comprehensive loss — 5 5 10 Net current period other comprehensive income (loss) (37 ) 1 2 (34 ) Balances at December 31, 2018 $ (65 ) $ (4 ) $ 9 $ (60 )

Fair Value Measurements

Fair Value Measurements	12 Months Ended
	Dec. 31, 2018
Fair Value Disclosures [Abstract]
Fair Value Measurements	Fair Value Measurement The Company’s fair value measurements incorporate various factors, including the credit standing and performance risk of the counterparties, the applicable exit market, and specific risks inherent in the instrument. Nonperformance and credit risk adjustments on risk management instruments are based on current market inputs when available, such as credit default hedge spreads. When such information is not available, internal models may be used. Assets and liabilities recorded at fair value in the consolidated financial statements are categorized based upon the level of judgment associated with the inputs used to measure their fair value. Hierarchical levels directly related to the amount of subjectivity associated with the inputs to valuation of these assets or liabilities are set forth below. Transfers between levels are recognized at the end of each quarter. The Company did not recognize any transfers between levels during the periods presented. Level 1—Inputs are unadjusted, quoted prices in active markets for identical assets or liabilities at the measurement date. Level 2—Inputs (other than quoted prices included in Level 1) are either directly or indirectly observable for the asset or liability through correlation with market data at the measurement date and for the duration of the instrument’s anticipated life. Level 3—Unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities and which reflect management’s best estimate of what market participants would use in pricing the asset or liability at the measurement date. Consideration is given to the risk inherent in the valuations technique and the risk inherent in the inputs to the model. Financial Instruments The carrying value of financial instruments classified as current assets and current liabilities approximates their fair value, based on the nature and short maturity of these instruments, and they are presented in the Company’s financial statements at carrying cost. Certain other assets and liabilities were measured at fair value upon initial recognition and unless conditions give rise to an impairment, are not remeasured. Financial Instruments Measured at Fair Value on a Recurring Basis The Company’s financial assets and liabilities which require fair value measurement on a recurring basis are classified within the fair value hierarchy as follows (in millions): December 31, 2018 Level 1 Level 2 Level 3 Total Assets Interest rate swaps $ — $ 3 $ — $ 3 Energy derivative — — 7 7 Foreign currency forward contracts — 12 — 12 Congestion revenue rights — — 1 1 $ — $ 15 $ 8 $ 23 Liabilities Interest rate swaps $ — $ 31 $ — $ 31 Foreign currency forward contracts — 2 — 2 Contingent consideration — — 130 130 $ — $ 33 $ 130 $ 163 December 31, 2017 Level 1 Level 2 Level 3 Total Assets Interest rate swaps $ — $ 2 $ — $ 2 Energy derivative — — 27 27 Foreign currency forward contracts — — — — $ — $ 2 $ 27 $ 29 Liabilities Interest rate swaps $ — $ 26 $ — $ 26 Foreign currency forward contracts — 3 — 3 Contingent consideration — — 22 22 $ — $ 29 $ 22 $ 51 Level 2 Inputs Derivative instruments subject to re-measurement are presented in the financial statements at fair value. The Company's interest rate swaps were valued by discounting the net cash flows using the forward LIBOR curve with the valuations adjusted by the Company’s credit default hedge rate. The Company’s foreign currency forward contracts were valued using the income approach based on the present value of the forward rates less the contract rates, multiplied by the notional amounts. Level 3 Inputs Energy Hedge The fair value of the energy derivative instrument is determined based on a third-party valuation model. The methodology and inputs are evaluated by management for consistency and reasonableness by comparing inputs used by the third-party valuation provider to another third-party pricing service for identical or similar instruments and also reconciling inputs used in the third-party valuation model to the derivative contract for accuracy. Any significant changes are further evaluated for reasonableness by obtaining additional documentation from the third-party valuation provider. The energy derivative instrument is valued by discounting the projected net cash flows over the remaining life of the derivative instrument using forward electricity prices with little or no market activity. Significant increases or decreases in this input would result in a significantly lower or higher fair value measurement. The following table presents a reconciliation of the energy derivative contract measured at fair value on a recurring basis using significant unobservable inputs (in millions): Energy Derivative 2018 2017 Balance, beginning of year $ 27 $ 41 Total gain (loss) included in electricity sales (3 ) 5 Settlements (17 ) (19 ) Balance, end of year $ 7 $ 27 During the years ended December 31, 2018 , 2017 and 2016 , the Company recognized losses of $20 million , $14 million , and $23 million relating to the energy derivative asset held at December 31, 2018 , 2017 and 2016 , respectively, which were recorded to energy sales in the consolidated statements of operations. Contingent Consideration As part of the Japan Acquisition, the Company is required to pay an additional earn-out of $118 million , which may be increased by $10 million if the final Tsugaru cost is less than or equal to the construction budget or may be decreased by $10 million if the final Tsugaru cost is greater than the construction budget, upon term conversion of the Tsugaru Construction Loan. The discounted fair value of the contingent consideration at the acquisition date was $103 million , subject to foreign currency exchange rate changes. In July 2018, the Company made a $3 million cash distribution payment to Pattern Energy Group LP upon term conversion of the Ohorayama construction loan in June 2018. The Broadview Project acquisition includes contingent consideration, which requires the Company to make an additional payment upon the commercial operation of the Grady Project, a wind project being separately developed by Pattern Development. The contingent post-closing payment reflects the fair value of the Company's interest in the increase in the projected 25 -year transmission wheeling revenue Western Interconnect will receive from the Grady Project, adjusted for the estimated production loss incurred by Broadview due to wake effects and transmission losses induced by the operation of the Grady Project. The fair value of the contingent consideration at the acquisition date was $21 million . The estimated fair value of the contingent considerations was calculated by using a discounted cash flow technique which utilized unobservable inputs. This fair value measurement is based on significant inputs not observable in the market and thus represent a Level 3 measurement as defined in ASC 820, Fair Value Measurement . As of December 31, 2018 , there were no significant changes in these unobservable inputs that may result in significant changes in fair value. The following table presents a reconciliation of the contingent consideration liability measured at fair value on a recurring basis using significant unobservable inputs (in millions): Contingent Consideration Liability 2018 2017 Balance, beginning of year $ 22 $ — Purchases 106 21 Total loss included in other income (expense), net 5 1 Settlements (3 ) — Balance, end of year $ 130 $ 22 During the years ended December 31, 2018 , and 2017 , the Company recognized loss on contingent liabilities of $2 million and $1 million , respectively, which were recorded to other income (expense), net in the consolidated statements of operations. Congestion Revenue Rights During the year ended December 31, 2018, the Company purchased $1 million of congestion revenue rights to hedge the financial risk of ERCOT-imposed congestion charges in the day-ahead market. Limited market data is available in the ERCOT auction and between auction dates; therefore, the Company utilizes historical prices to forecast forward prices. During the year ended December 31, 2018 , the Company recognized loss on congestion revenue rights of less than $1 million , which was recorded to gain (loss) on derivatives in the consolidated statements of operations. The valuation techniques and significant unobservable inputs used in recurring Level 3 fair value measurements were as follows (in millions, for fair value): December 31, 2018 Fair Value Valuation Technique Significant Unobservable Inputs Range Energy derivative $7 Discounted cash flow Forward electricity prices $20.02 - $32.58 (1) Discount rate 2.80% - 2.81% Broadview contingent consideration $25 Discounted cash flow Discount rate 4.0% - 8.0% Annual energy production loss 0.70% Tsugaru contingent consideration $105 Discounted cash flow Deferred purchase price $109 - $128 million Discount rate 6.90% Congestion revenue rights $1 Market approach Auction prices $2.48 - $8.23 (1) December 31, 2017 Fair Value Valuation Technique Significant Unobservable Inputs Range Energy derivative $27 Discounted cash flow Forward electricity prices $14.44 - $71.45 (1) Discount rate 1.69% - 1.96% Broadview contingent consideration $22 Discounted cash flow Discount rate 4.0% - 8.0% Annual energy production loss 1.0% (1) Represents price per MWh Financial Instruments not Measured at Fair Value The following table presents the carrying amount and fair value and the fair value hierarchy of the Company’s financial liabilities that are not measured at fair value in the consolidated balance sheets, but for which fair value is disclosed (in millions): Fair Value As reflected on the balance sheet Level 1 Level 2 Level 3 Total December 31, 2018 Total debt, net $ 2,283 $ — $ 2,240 $ — $ 2,240 December 31, 2017 Total debt, net $ 1,931 $ — $ 1,938 $ — $ 1,938 Long-term debt is presented on the consolidated balance sheets, net of financing costs, discounts and premiums. The fair value of variable interest rate long-term debt is approximated by its carrying cost. The fair value of fixed interest rate long-term debt is estimated based on observable market prices or parameters or derived from such prices or parameters. Where observable prices or inputs are not available, valuation models are applied, using the net present value of cash flow streams over the term using estimated market rates for similar instruments and remaining terms.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes The following table presents significant components of the provision for income taxes (in millions): Year ended December 31, 2018 2017 2016 Current: Federal $ — $ — $ — State — — — Foreign 16 — — Total current expense 16 — — Deferred: Federal — (3 ) — State — — — Foreign 16 15 9 Total deferred expense 16 12 9 Total provision for income taxes $ 32 $ 12 $ 9 The following table presents the domestic and foreign components of net loss before income tax provision (in millions): Year ended December 31, 2018 2017 2016 U.S. $ (158 ) $ (119 ) $ (71 ) Foreign 121 49 28 Total $ (37 ) $ (70 ) $ (43 ) The following table presents a reconciliation of the statutory U.S. federal income tax rate to the Company’s effective tax rate, as a percentage of income before taxes for the following periods: Year ended December 31, 2018 2017 2016 Computed tax at statutory rate 21.0 % 35.0 % 35.0 % Adjustment for income in non-taxable entities allocable to noncontrolling interests (125.2 )% (32.6 )% (25.6 )% Foreign rate differential Tax rate differential on pre-tax book income (16.1 )% 6.4 % 0.7 % Dual taxpaying entities outside basis difference (78.5 )% (23.0 )% (17.6 )% Local tax on branch profits/(losses)—Puerto Rico (0.1 )% 0.1 % — % Permanent book/tax differences (domestic only) 0.5 % (0.1 )% (0.2 )% Valuation allowance change 38.9 % 47.7 % (18.8 )% Subpart F income (7.9 )% (3.5 )% — % Capital gain exclusion - sale of partnership interest 24.7 % — % — % Contingent consideration accretion (4.9 )% — % — % Impairment 1.4 % — % — % Tax credits 61.7 % 31.6 % 7.6 % Effect of U.S. tax rate change under Tax Cuts and Jobs Act — % (78.1 )% — % Other (2.5 )% (0.1 )% (0.9 )% Effective income tax rate (87.0 )% (16.6 )% (19.8 )% Significant components of the Company’s deferred tax assets and liabilities are as follows (in millions): Year ended December 31, 2018 2017 Deferred tax assets: Accruals and prepaids $ 3 $ 3 Basis difference in derivatives 3 — Hatchet Ridge financing 17 17 Asset retirement obligation 32 6 Unrealized loss on derivatives — 2 Net operating loss carryforwards 230 274 Foreign currency translation adjustments 2 3 Other deferred tax assets 12 2 Tax credits 118 42 Total gross deferred tax assets 417 349 Less: Valuation allowance (175 ) (141 ) Total gross deferred tax assets net of valuation allowance $ 242 $ 208 Deferred tax liabilities: Property, plant and equipment $ (215 ) $ (189 ) Intangibles (24 ) — Partnership interest (108 ) (65 ) Deferred interest, commitment fees and financing costs (2 ) (2 ) Unrealized gain on derivatives (2 ) — Basis difference in subsidiaries (2 ) (1 ) Other deferred tax liabilities (1 ) (1 ) Total gross deferred tax liabilities (354 ) (258 ) Total net deferred tax assets/(liabilities) $ (112 ) $ (50 ) On December 22, 2017, the Tax Act was enacted into law. The Tax Act contained several key provisions that affected corporations, including a reduction in the U.S. federal corporate income tax rate from 35% to 21% , effective January 1, 2018. Included in the key provisions are a transition from a worldwide system of taxation to a primarily territorial tax system accompanied by a tax on deemed repatriation of undistributed and previously untaxed non-U.S. earnings, a tax on global intangible low-taxed income (“GILTI”), a tax determined by base erosion and anti-abuse benefits (BEAT) from certain payments between a U.S. corporation and foreign subsidiaries, a limitation on deductible executive compensation, and a net business interest expense limitation. In December 2017, the SEC staff issued Staff Accounting Bulletin No. 118 (“SAB 118”) which provides guidance on accounting for the tax effects of the Tax Act. SAB 118 provides a measurement period, not to exceed one year from the date of enactment, for companies to complete the accounting related to the Tax Act under ASC 740. As of December 2018, the Company had completed its accounting for the tax effects of the Tax Act. As part of the completion of such accounting, the Company elected to account for GILTI as a period cost. The U.S. operations are in a net deferred tax asset position offset by a full valuation allowance. The change in net deferred tax assets before valuation allowance during the period ended December 31, 2018 includes deferred tax assets established for potential U.S. foreign tax credits of $52 million that may be generated by the reversal of the deferred tax liability related to temporary differences from Japan operations that were acquired in 2018 and are conducted through a branch for U.S. tax purposes. While the companies are disregarded entities for U.S. tax purposes, they are corporations for local tax purposes and are therefore subject to local and U.S. taxation. In 2018, the Company operated entities in Canada, Japan, and Chile that are taxed in both local jurisdictions and the U.S. The Company's tax rate reflects the impact of double taxation from these entities. On December 31, 2018, Pattern Canada Financing Company (“PCFC”) sold its entire minority interest in the K2 project for a net tax gain for Canada tax purposes of $12 million after utilization of a net operating loss carryforward and other tax attributes. The Company recorded a valuation allowance against the majority of its deferred tax assets as of December 31, 2017 and December 31, 2018. The Company intends to continue maintaining a valuation allowance on certain deferred tax assets until there is sufficient evidence to support the reversal of all or some portion of these allowances. However, given its current earnings and anticipated future earnings, it believes there is a reasonable possibility that within the next 12 months, sufficient positive evidence may become available to allow it to reach a conclusion that a portion of the valuation allowance will no longer be needed. Release of a portion or all of the valuation allowance would result in the recognition of certain deferred tax assets and a decrease to income tax expense for the period the release is recorded. However, the exact timing and amount of the valuation release are subject to change on the basis of the level of profitability that the Company is able to achieve. The net change in valuation allowance was an increase of $34 million for the tax year ended December 31, 2018. The increase was primarily driven by potential U.S. foreign tax credits related to Japan branch operations partially offset by a decrease of operating losses in the U.S. federal and state jurisdictions. As of December 31, 2018 , the Company has U.S federal and state net operating loss (NOL) carryforwards in the amount of $959 million and $190 million , respectively, which begin to expire in the year ending December 31, 2034 for federal and state purposes. The Company also has foreign net operating loss carryforwards in Canada in the amount of $31 million which begin to expire in the year ending December 31, 2029, foreign net operating loss carryforwards in Puerto Rico of $4 million that begins to expire in the year ending December 31, 2022, and foreign net operating loss carryforwards in Japan of $13 million that can be carried forward indefinitely. The Company's production tax credits of $17 million begin to expire in the year ending December 31, 2033. Internal Revenue Code Section 382 places a limitation (the Section 382 limitation) on the amount of taxable income that can be offset by NOL and credit carryforwards, as well as built-in losses, after a change in control (generally greater than 50% change in ownership) of a loss corporation. California has similar rules. The Company did not have any historic U.S. NOLs prior to October 2, 2013 except for NOLs from its Puerto Rico entity which may be subject to Section 382 limitation. The Company experienced a change in ownership on May 14, 2014. As a result, the Company’s NOL carryforwards and credits generated through the date of change are subject to an annual limitation under Section 382. If the Company generates sufficient taxable income, its pre-change NOLs and credits are not expected to expire unutilized due to a Section 382 limitation. The Company is required to recognize in the financial statements the impact of a tax position, if that position is not more likely than not of being sustained on audit, based on the technical merits of the position. As of December 31, 2018 , the Company does not have any unrecognized tax benefits and does not have any tax positions for which it is reasonably possible that the amount of gross unrecognized tax benefits will increase or decrease within 12 months after the year ended December 31, 2018 . The Company files income tax returns in the U.S. federal jurisdiction, various state jurisdictions and foreign jurisdictions in Canada, Japan and Puerto Rico. The Company’s U.S., Canada and Puerto Rico income tax returns for 2015 and forward are subject to examination by taxing authorities. The statute of limitations in Japan is generally five years from the date of filing, plus extension. The Japan statute of limitations for transfer pricing is six years from the date of filing, and net operating losses generally extend the statute to ten years, depending on the year in which the loss originated. The Company has a policy to classify accrued interest and penalties associated with uncertain tax positions together with the related liability, and the expenses incurred related to such accruals are included in the provision for income taxes. The Company did not incur any interest expenses or penalties or have outstanding liabilities on the balance sheet associated with unrecognized tax benefits for the year ended December 31, 2018 . The Company operates under a tax holiday in Puerto Rico which enacted a special tax rate of 4% for businesses dedicated to the production of energy for the consumption through the use of renewal sources. Act 73 of May 28, 2008 as amended, known as the "Economic Incentives for the Development of Puerto Rico Act" (the "Act"), promotes the development of green energy projects through economic incentives so as to reduce the island's dependency on oil. On September 15, 2016, the Company commenced operations under the Act 83 Grant while simultaneously surrendering operations under Act 73 Grant. The Act 83 Grant affords the Company identical tax benefits to the Act 73 Grant but has a duration of 25 years , thereby extending the Grant benefit for 25 years at the date of conversion. The Act 83 Grant continues to provide for a 4% reduced income tax rate in Puerto Rico, and is scheduled to terminate on December 31, 2041. The impact of the tax holiday decreased foreign deferred tax expense by $0.4 million for the year ended December 31, 2018 . The impact of the tax holiday on basic and diluted net income per share of Class A common stock for the year ended December 31, 2018 was $0.004 .

Stockholders' Equity

Stockholders' Equity	12 Months Ended
	Dec. 31, 2018
Equity [Abstract]
Stockholders' Equity	Stockholders' Equity Preferred Stock The Company has 100,000,000 shares of authorized preferred stock issuable in one or more series. The Company’s Board of Directors is authorized to determine the designation, powers, preferences and relative, participating, optional or other special rights of any such series. As of December 31, 2018 and 2017 , there was no preferred stock issued and outstanding. Common Stock On October 23, 2017, the Company completed an underwritten public offering of its Class A common stock. In total, 9,200,000 shares of the Company's Class A common stock were sold at a public offering price of $23.40 per share. This includes 1,200,000 shares purchased by the underwriters to cover over-allotments. Aggregate net proceeds of the equity offering, including the proceeds of the over-allotment option, were approximately $212 million after deduction of underwriting discounts, commissions, and transaction expenses. On August 12, 2016, the Company completed an underwritten public offering of its Class A common stock. In total, 10,000,000 shares of the Company's Class A common stock were sold. In connection with the equity offering, the underwriters had a 30-day option to purchase up to an additional 1,500,000 shares of Class A common stock to cover over-allotments. On August 22, 2016, the underwriters partially exercised their over-allotment option and purchased an additional 1,300,000 shares of Class A common stock. Aggregate net proceeds of the equity offering, including the proceeds of the over-allotment option, were approximately $259 million after deduction of underwriting discounts, commissions, and transaction expenses. On May 9, 2016, the Company entered into an Equity Distribution Agreement with RBC Capital Markets, LLC, KeyBanc Capital Markets Inc. and Morgan Stanley & Co. LLC (collectively, the Agents). Pursuant to the terms of the Equity Distribution Agreement, the Company may offer and sell shares of the Company’s Class A common stock, par value $0.01 per share, from time to time through the Agents, as the Company’s sales agents for the offer and sale of the shares, up to an aggregate sales price of $200 million . For the year ended December 31, 2018, the Company did not sell any shares under the Equity Distribution Agreement. For the years ended December 31, 2017 and 2016, the Company sold 1,068,261 and 1,240,504 shares, respectively, under the Equity Distribution Agreement; net proceeds under the issuances were $25 million and $28 million and the aggregate compensation paid by the Company to the Agents with respect to such sales was less than $1 million for December 31, 2017 and 2016, respectively. As of December 31, 2018, approximately $144 million in aggregate offering price remained available to be sold under the agreement. Voting Rights Holders of the Company’s Class A common stock as of December 31, 2018 are entitled to one vote per share on all matters submitted to a vote of stockholders and will vote as a single class under all circumstances. Noncontrolling Interests The following table presents the balances for noncontrolling interests by project (in millions). December 31, 2018 2017 El Arrayán (1) $ — $ 32 Logan's Gap 132 171 Panhandle 1 131 175 Panhandle 2 176 208 Post Rock 116 160 Amazon Wind 101 134 Broadview Project 257 308 Futtsu 10 — Meikle 57 66 MSM 37 — Stillwater 95 — Noncontrolling interests $ 1,112 $ 1,254 (1) Noncontrolling interest of El Arrayán was derecognized as a result of the sale of the Company's operation in Chile. The following table presents the components of total noncontrolling interests as reported in stockholders’ equity in the consolidated balance sheets (in millions). Capital Accumulated Income (Loss) Accumulated Other Comprehensive Income (Loss) Noncontrolling Interests Balances at December 31, 2015 $ 972 $ (27 ) $ (1 ) $ 944 Distributions to noncontrolling interests (18 ) — — (18 ) Net loss — (35 ) — (35 ) Other comprehensive income, net of tax — — — — Balances at December 31, 2016 954 (62 ) (1 ) 891 Acquisitions 390 — — 390 Distributions to noncontrolling interests (20 ) — — (20 ) Partial sale of subsidiary 56 — — 56 Net loss — (64 ) — (64 ) Other comprehensive income, net of tax — — 1 1 Balances at December 31, 2017 $ 1,380 $ (126 ) $ — $ 1,254 Acquisitions 49 — — 49 Contribution from noncontrolling interests 98 — — 98 Distributions to noncontrolling interests (38 ) — — (38 ) Sale of subsidiaries (37 ) 5 — (32 ) Net loss (1) — (211 ) — (211 ) Other comprehensive loss, net of tax — — (8 ) (8 ) Balances at December 31, 2018 $ 1,452 $ (332 ) $ (8 ) $ 1,112 (1) On December 22, 2017, the Tax Act was signed into law, which enacted major changes to the U.S. federal income tax laws, including a permanent reduction in the U.S. federal corporate income tax rate from 35% to 21%, effective January 1, 2018. Reduction in the corporate income tax rate resulted in a one-time reduction in the noncontrolling interests attributable to partners in its tax equity partnerships. As part of the liquidation waterfall, the Company allocated significantly lower portions of the hypothetical liquidation proceeds to compensate certain noncontrolling interest investors for tax gains on the hypothetical sale calculated at the lowered rate of 21% as compared to the rate of 35% that was previously utilized. For the year ended December 31, 2018, included in net loss attributable to noncontrolling interests is a one-time adjustment of $150 million as a result of the decrease in the federal corporate income tax rate. Pay-go Contribution The Broadview Acquisition includes a partial pay as you go (Pay-go) funding arrangement under which, when the actual annual MWh production of Broadview exceeds a certain production threshold, the tax equity investors are obligated to make a cash contribution ("Pay-go contribution") to the Company. The Pay-go arrangement resulted in a lower initial investment by the tax equity partners and provided them with some protection from potential underperformance of Broadview. For the year ended December 31, 2018 , the actual MWh production of Broadview exceeded the production threshold which resulted in a Pay-go contribution receivable from the tax equity partners in the amount of approximately $4 million . The Company classified the receivable as a component of noncontrolling interests in the accompanying consolidated balance sheets. The Company expects to receive the Pay-go contribution by the end of the first quarter of 2019. Allocations of Distributions and Tax Allocations for Tax Equity Partnerships Generally, tax equity partnerships have specific commercial terms that dictate distributions of cash and allocation of tax items among the partners, who are divided into one of two categories: tax equity and cash investor. A disproportionate share of income and cash is given to tax equity in order for them to achieve a target after-tax yield or “flip” near year 10 of project operations. The target yield and flip term vary by agreement and are dependent on project performance. Prior to the flip, tax items (income, US Federal production tax credits) are commonly allocated 99% to the tax equity. On the other hand, distributable cash is divided among the partners in percentages that do not match the tax items. Cash distribution percentages can be temporarily increased for tax equity in the event that certain cumulative distribution thresholds are not achieved. Once tax equity reaches their target yield, the allocations and distributions “flip” to different amounts. After the flip, income and cash are typically allocated 5% to the tax equity and 95% to the cash investor. REC sales are often specially addressed in each agreement with most of the cash and income directed to the cash investor both pre and post-flip. Tax equity partnerships imposes a range of affirmative and negative covenants that are similar to what a term lender would require, such as, financial reporting, insurance maintenance and prudent operator standards. Most of these restrictions end once the flip point occurs and any deficit restoration obligation of the tax equity has been eliminated. There are also covenants that specifically seek to preserve the tax attributes of the project that are not customary for project term lenders. If tax equity suffers any losses or damages as the result of a breach of representation, covenant, or other obligation by the cash investor in its capacity as managing member, tax equity may provide notice to the cash investor and require that any distributions otherwise required to be paid to the cash investor shall, instead, be paid to tax equity to cover any damages.

Equity Incentive Award Plan

Equity Incentive Award Plan	12 Months Ended
	Dec. 31, 2018
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Equity Incentive Award Plan	Equity Incentive Award Plan Under the Amended and Restated 2013 Equity Incentive Award Plan (2013 Plan), the Company may issue 3,000,000 aggregate number of shares of Class A common stock for equity awards including incentive and nonqualified stock options, restricted stock awards (RSAs) and restricted stock units (RSUs) to employees, directors and consultants. RSAs provide the holder with immediate voting rights, but are restricted in all other respects until released. RSUs generally entitle the holders the right to receive the underlying shares of the Company's Class A common stock upon vesting. Upon cessation of services to the Company, any nonvested RSAs and RSUs will be forfeited. All nonvested RSAs and RSUs accrue dividends and distributions, which are subject to vesting and paid in cash upon release. Accrued dividends and distributions are forfeitable to the extent that the underlying awards do not vest. As of December 31, 2018 , there were 1,780,006 aggregate number of Class A shares available for issuance under the 2013 Plan. Stock-Based Compensation Stock-based compensation expenses related to, RSAs, RSUs and stock options are recorded as a component of general and administrative expenses in the Company’s consolidated statements of operations and totaled $5 million , $5 million and $5 million for the years ended December 31, 2018 , 2017 and 2016 , respectively. Restricted Stock Awards The Company granted time-based RSAs to certain employees and independent directors. The Company measures the fair value of the RSAs at the grant date and accounts for stock-based compensation by amortizing the fair value on a straight line basis over the related vesting period. The following table summarizes RSA activity under the 2013 Plan for the year ended December 31, 2018 : Shares Weighted-Average Grant-Date Nonvested at December 31, 2017 110,579 $ 19.26 Granted 138,817 $ 18.67 Vested (127,268) $ 19.03 Nonvested at December 31, 2018 122,128 $ 18.84 For the years ended December 31, 2018 , 2017 and 2016 , the total fair value of RSAs vested was $3 million , $3 million and $2 million , respectively. The weighted-average grant date fair values per RSA granted during the same periods were $18.67 , $20.35 and $18.76 , respectively. As of December 31, 2018 , the total unrecorded stock-based compensation expense for nonvested RSAs was $2 million , which is expected to be amortized over a weighted-average period of 1.7 years . RSAs that contain Market Conditions The Company granted TSR-RSAs to certain senior management personnel. The number of awards granted represented the target number of shares of Class A common stock that may be earned; however, the number of vested TSR-RSAs is assessed at the end of a three -year performance period in accordance with the level of total shareholder return of the Company's stock price achieved relative to a peer group during the specified period. Following the date of grant, rights to dividends will accrue on the maximum number of shares and may be forfeited if the market or service conditions are not achieved. The Company measures the fair value of these restricted stock awards at the grant date using a Monte Carlo simulation model and amortizes the fair value over the longer of the requisite period or performance period. The Company estimates expected volatility based on the actual volatility of the Company's daily closing share price since listing on September 27, 2013 and the historical volatility of comparable publicly traded companies for a period that is equal to the performance period. The risk-free interest rate is based on the yield on U.S. government bonds for a period commensurate with the performance period. The assumptions used to estimate the fair value of TSR-RSAs are as follows: Years ended December 31, 2018 2017 2016 Expected stock price volatility (1) 32% 34% 35% Expected dividend yield N/A N/A N/A Risk-free interest rate 2.38% 1.60% 1.11% Expected performance period in years (2) 2.8 2.8 2.8 (1) The expected volatility was estimated using the historical volatility derived from the Company's Class A common stock. (2) The expected performance period was estimated based on the length of the remaining performance period from the grant date. The following table summarizes TSR-RSAs activity under the 2013 Plan for the year ended December 31, 2018 : Shares Weighted-Average Grant-Date Nonvested at December 31, 2017 218,877 $ 25.07 Granted 97,610 $ 18.20 Vested (56,844 ) 39.16 Nonvested at December 31, 2018 259,643 $ 19.40 For the years ended December 31, 2018 , 2017 , and 2016 , the weighted-average grant-date fair value per TSR-RSAs granted was $18.20 , $19.48 and $20.63 , respectively. As of December 31, 2018 , the total unrecorded stock-based compensation expense related to nonvested TSR-RSAs was $2 million , which is expected to be amortized over a weighted-average period of 1.8 years . Restricted Stock Units In 2018 , 2017 and 2016 , the Company granted time-based deferred RSUs to certain independent directors. Deferred RSUs are equity awards that entitle the holder the right to receive shares of the Company's Class A common stock upon vesting and are settled on, or as soon as administratively possible after the settlement date which is January 1 following the date of the director's termination of service. The Company measures the fair value of deferred RSUs at the grant date and accounts for stock-based compensation by amortizing the fair value on a straight line basis over the related vesting period. During the year ended December 31, 2018 , there were RSU grants of 25,885 shares, all of which vested. The total fair value of deferred RSUs vested for the years ended December 31, 2018 , 2017 and 2016 , was less than a million dollars, $1 million and $1 million , respectively. The weighted-average grant date fair value of stock awards granted during the same periods was $21.49 , $18.99 and $20.29 , respectively. As of December 31, 2018, there were no nonvested deferred RSUs. Stock Options During the years ended December 31, 2018 , 2017 and 2016 , no options were granted or exercised. A summary of option activity under the employee share option plan as of December 31, 2018 , and changes during the year then ended is presented below. Shares Weighted-Average Exercise Price Weighted Average Remaining Contractual Life Aggregate Intrinsic Value (in millions) Outstanding at December 31, 2017 411,323 $ 22.00 Forfeited or expired (29,169 ) $ 22.00 Outstanding at December 31, 2018 382,154 4.7 — Exercisable at December 31, 2018 382,154 4.7 —

Earnings (Loss) Per Share

Earnings (Loss) Per Share	12 Months Ended
	Dec. 31, 2018
Earnings Per Share [Abstract]
Earnings (Loss) Per Share	Earnings (Loss) Per Share Basic earnings (loss) per share is computed by dividing net earnings (loss) attributable to common stockholders by the weighted average number of common shares outstanding during the reportable period. Diluted earnings (loss) per share is computed by adjusting basic earnings (loss) per share for the effect of all potential common shares unless they are anti-dilutive. For purposes of this calculation, potentially dilutive securities are determined by applying the treasury stock method to the assumed exercise of in-the-money stock options and the assumed vesting of outstanding RSAs and release of deferred RSUs. Potentially dilutive securities related to convertible senior notes are determined using the if-converted method. The Company's vested deferred RSUs have non-forfeitable rights to dividends prior to release and are considered participating securities. Accordingly, they are included in the computation of basic and diluted earnings per share, pursuant to the two-class method; however, due to amounts being well below $1 million dollars, they are not shown in the table below. Under the two-class method, distributed and undistributed earnings allocated to participating securities are excluded from net earnings (loss) attributable to common stockholders for purposes of calculating basic and diluted earnings (loss) per share. However, net losses are not allocated to participating securities since they are not contractually obligated to share in the losses of the Company. Potentially dilutive securities excluded from the calculation of diluted earnings (loss) per share because their effect would have been anti-dilutive were 9 million, 9 million and 8 million, respectively, for the years ended December 31, 2018 , 2017 and 2016 . The computations for Class A basic and diluted earnings (loss) per share are as follows (in millions except share data): Year ended December 31, 2018 2017 2016 Numerator for basic and diluted earnings (loss) per share: Net income (loss) attributable to Pattern Energy $ 142 $ (18 ) $ (17 ) Less: earnings allocated to participating securities — — — Net income (loss) attributable to common stockholders $ 142 $ (18 ) $ (17 ) Denominator for earnings (loss) per share: Weighted average number of shares: Class A common stock - basic 97,456,407 89,179,343 79,382,388 Add dilutive effect of: Restricted stock awards 193,910 — — Restricted stock units 1,184 — — Class A common stock - diluted 97,651,501 89,179,343 79,382,388 Earnings (loss) per share: Class A common stock: Basic $ 1.45 $ (0.20 ) $ (0.22 ) Diluted $ 1.45 $ (0.20 ) $ (0.22 ) Dividends declared per Class A common share $ 1.69 $ 1.67 $ 1.58

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2018
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies Commitments The following table summarizes estimates of future commitments related to the various agreements that the Company has entered into as of December 31, 2018 (in millions): 2019 2020 2021 2022 2023 Thereafter Total Transmission service agreements (1) $ 24 $ 24 $ 24 $ 24 $ 24 $ 495 $ 615 Operating leases (2) 22 21 22 21 22 352 460 Service and maintenance agreements 32 30 30 27 26 68 213 Construction and other commitments 192 155 4 3 3 34 391 Total commitments $ 270 $ 230 $ 80 $ 75 $ 75 $ 949 $ 1,679 (1) Future commitments under the transmission service agreements are based on current rates, which are subject to future changes. (2) Certain operating leases have adjustments for market provisions. Amounts in the above table represent the best estimates of future payments to be made under these leases. Transmission Service Agreements In connection with the Broadview Project acquisition, the Company became a party to various long-term transmission service agreements expiring between 3 - 29 years. The Company recorded transmission service costs related to such agreements of $25 million for the year ended December 31, 2018 . Operating Leases The Company has entered into various non-cancellable long-term operating lease agreements related to offices and lands for its wind farms expiring between 1 - 40 years. Certain of these arrangements contain contingent rental payment provisions based upon the volume of electricity generated at a particular windfarm. The Company recognizes rent expense under such arrangements on a straight-line basis. For the years ended December 31, 2018 , 2017 and 2016 , the Company recorded rent expenses of $18 million , $15 million and $13 million , respectively, in project expense in its consolidated statements of operations. In March 2018, the Company entered into an operating lease for its new corporate headquarters in San Francisco, California. Total operating lease payments are approximately $35 million over the term of the lease which expires in December 2028. Service and Maintenance Agreements The Company has entered into service and maintenance agreements with third party contractors to provide turbine operations and maintenance services and modifications and upgrades for varying periods over the next 22 years . The computation of outstanding commitments includes an estimated annual price adjustment for inflation of 2% , where applicable. For the years ended December 31, 2018 , 2017 and 2016 , the Company recorded service and maintenance expense under these agreements of $38 million , $47 million and $53 million , respectively, in project expense in its consolidated statements of operations. Construction and Other Commitments Included in construction and other commitments are payments in lieu of taxes, Tsugaru construction, Gulf Wind re-powering, and various other commitments related to the Company's projects and operations of its business. Payments in lieu of taxes include payments the Company is required to make in lieu of taxes as a result of tax savings realized as part of the issuance of the industrial revenue bonds. See Note 7 , Intangible Assets and Liabilities and Goodwill , for further discussion. Tsugaru is currently in construction and expected to commence commercial operations in early to mid-2020. Gulf Wind Re-Powering Commitment In September 2018, the Company committed to a plan to re-power the Gulf Wind project. In connection with the re-powering plan, the Company entered into a turbine purchase agreement for a maximum purchase price of $151 million plus certain storage costs, depending upon the number of turbines purchased. The Company has the option, exercisable by September 2, 2019, to reduce the number of turbines. Separately, in September 2018, the Company exercised its option to purchase turbines from an affiliate of Pattern Development. Such affiliate of Pattern Development has until August 30, 2019 to determine the number of turbines to sell to the Company. Letters of Credit Power Sale Agreements The Company owns and operates wind and solar power projects, and has entered into various long-term PSAs that terminate from 2019 to 2043 . The terms of these agreements generally provide for the annual delivery of a minimum amount of electricity at fixed prices and in some cases include price escalation over the term of the agreement. Under the terms of these agreements, as of December 31, 2018 , irrevocable letters of credit totaling $156 million were available to be issued to guarantee the Company's performance for the duration of the agreements. Project Finance and Lease Agreements The Company has various project finance and lease agreements which obligate the Company to provide certain reserves to enhance its credit worthiness and facilitate the availability of credit. As of December 31, 2018 , irrevocable letters of credit totaling $170 million which includes letters of credit available under the Revolving Credit Facility were available to be issued to ensure performance under these various project finance and lease agreements. Contingencies Turbine Operating Warranties and Service Guarantees The Company has various turbine availability warranties from its turbine manufacturers and service guarantees from its service and maintenance providers. Pursuant to these guarantees, if a turbine operates at less than minimum availability during the guarantee measurement period, the service provider is obligated to pay, as liquidated damages at the end of the warranty measurement period, an amount for each percent that the turbine operates below the minimum availability threshold. In addition, pursuant to certain of these guarantees, if a turbine operates at more than a specified availability during the guarantee measurement period, the Company has an obligation to pay a bonus to the service provider at the end of the warranty measurement period. As of December 31, 2018 , the Company recorded liabilities of less than $1 million associated with bonuses payable to turbine manufacturers and service providers. Contingencies in connection with the Broadview Project Acquisition The Company recorded a $7 million contingent obligation, payable to a third party who holds a 1% interest in Western Interconnect, at fair value upon the acquisition of the Broadview Project. These contingent payments are subject to certain conditions, including the actual energy production of Broadview in a production year and the continued operation of Broadview. Additionally, the Company initially recorded a $29 million contingent obligation, payable to the same counterparty, at fair value using a discount rate of approximately 5% upon the acquisition of the Broadview Project. The undiscounted contingent obligation is estimated to be approximately $50 million and is expected to be paid over the life of the PSA term. These contingent payments are subject to certain conditions, including the commercial operation of the Grady Project. The contingent payment is calculated as a percentage of additional transmission revenue earned by Western Interconnect upon the Grady Project's commercial operation. Contingencies in connection with the Sale of Panhandle 2 interests In connection with the sale of Panhandle 2, the Company agreed to indemnify PSP Investments up to $5 million to cover PSP Investments' pro rata share of the economic impacts resulting from planned transmission outages in the Texas market until December 31, 2019. As of December 31, 2018 , the Company recorded a contingent liability of $4 million associated with the indemnity. Legal Matters From time to time, the Company has become involved in claims and legal matters arising in the ordinary course of business. Management is not currently aware of any matters that will have a material adverse effect on the financial position, results of operations, or cash flows of the Company. Indemnity The Company provides a variety of indemnities in the ordinary course of business to contractual counterparties and to its lenders and other financial partners. The Company is party to certain indemnities for the benefit of project finance lenders and tax equity partners of certain projects. The Company also enters into indemnity agreements in the ordinary course of business with surety bond providers that issue surety bonds to contractual counterparties in connection with the decommissioning projects and other performance obligations. Pursuant to the indemnity agreements, the Company is obligated, on a joint and several basis with the project company, to indemnify the surety in the event of a draw by the beneficiary. The indemnity obligation is limited to the amount of the bonds and certain related costs and expenses.

Related Party Transactions

Related Party Transactions	12 Months Ended
	Dec. 31, 2018
Related Party Transactions [Abstract]
Related Party Transactions	Related Party Transactions Management fees The Company provides management services and receives a fee for such services under agreements with its joint venture investees, South Kent, Grand, and Armow, in addition to various Pattern Energy Group LP subsidiaries and equity method investments. In connection with the Japan Acquisition, the Company receives management services related to the acquired projects and incurred a fee for such services under agreements with a subsidiary of Pattern Development in 2018. Management Services Agreement and Shared Management The Company has entered into a MSA with the Pattern Development Companies, which provides for the Company and the Pattern Development Companies to benefit, primarily on a cost-reimbursement basis, from the parties’ respective management and other professional, technical and administrative personnel, all of whom report to the Company’s executive officers. Costs and expenses incurred at the Pattern Development Companies or their respective subsidiaries on the Company's behalf will be allocated to the Company. Conversely, costs and expenses incurred at the Company or its respective subsidiaries on the behalf of a Pattern Development Company will be allocated to the respective Pattern Development Company. Pursuant to the MSA, certain of the Company’s executive officers, including its Chief Executive Officer (shared PEG executives), also serve as executive officers of the Pattern Development Companies and devote their time to both the Company and the Pattern Development Companies as is prudent in carrying out their executive responsibilities and fiduciary duties. The shared PEG executives have responsibilities for both the Company and the respective Pattern Development Companies and, as a result, these individuals do not devote all of their time to the Company’s business. Under the terms of the MSA, each of the respective Pattern Development Companies is required to reimburse the Company for an allocation of the compensation paid to such shared PEG executives reflecting the percentage of time spent providing services to such Pattern Development Company. Employee Savings Plan The Company participates in a 401(k) plan sponsored and maintained by Pattern Energy Group LP. For the years ended December 31, 2018 , 2017 and 2016 , the Company contributed $1 million , $1 million and $1 million , respectively, which was recorded as general and administrative expense on the consolidated statements of operations. Related Party Transactions The table below presents amounts due from and to related parties as included in the consolidated balance sheets for the following periods (in millions): December 31, 2018 2018 2017 Other current assets $ 7 $ 13 Total due from related parties $ 7 $ 13 Other current liabilities $ 9 $ 11 Contingent liabilities, current 25 — Contingent liabilities 105 21 Total due to related parties $ 139 $ 32 The table below presents the revenue, reimbursement and (expenses) recognized for management services and under the MSA, as included in the statements of operations for the following periods (in millions): Years Ended December 31, Related Party Agreement Financial Statement Line Item 2018 2017 2016 Management fees Other revenue $ 9 $ 8 $ 6 Management fees Project expense $ 1 $ — $ — MSA reimbursement General and administrative $ 12 $ 12 $ 5 MSA costs Related party general and administrative expense $ (15 ) $ (14 ) $ (10 ) Purchase and Sales Agreements During the years ended December 31, 2018 , and 2017, the Company consummated the following investment and acquisitions with Pattern Energy Group LP and Pattern Development which are further detailed in Note 5 , Acquisitions (in millions): Acquisitions from Pattern Development Companies Date of Acquisition Cash consideration net of acquired cash Debt Assumed Contingent Consideration Japan projects March 7, 2018 $ 158 $ 181 $ 106 MSM August 10, 2018 $ 31 $ 196 $ — Stillwater Wind LLC November 20, 2018 $ 17 $ — $ — Broadview Project April 21, 2017 $ 169 $ 51 $ 21 Meikle August 10, 2017 $ 58 $ 266 $ — Investment in Pattern Development During 2018, the Company funded $115 million into Pattern Development of which approximately $23 million was used by Pattern Development to fund the redemption of Pattern Energy Group LP's interest. As of December 31, 2018 , the Company has funded $183 million in aggregate and holds an approximate 29% ownership interest in Pattern Development 2.0. Development Fee In September 2018, upon reaching a project development milestone, Tsugaru paid a development fee of approximately $15 million to an affiliate of Pattern Development. Due to the Company's equity ownership in Pattern Development, the Company has eliminated its portion of the profits realized by Pattern Development with respect to this transaction. PSP Investments Joint Venture In June 2017, the Company entered into a Joint Venture Agreement with PSP Investments pursuant to which PSP Investments will have the right to co-invest up to an aggregate amount of approximately $500 million in projects acquired by the Company under Project Purchase Rights with the Pattern Development Companies, including investments in Meikle, MSM and Panhandle 2. PSP Investments acquired a 49% interest in Meikle and 49% of Class B membership in Panhandle 2 in 2017 and 49% interest in MSM and 49% of Class B membership in Stillwater in 2018. Prior to December 31, 2018, PSP Investments previously purchased approximately 9 million shares of the Company's common stock from Pattern Energy Group LP and an additional approximately 600,000 shares from the Company. Sponsor Services Agreement On June 16, 2017, the Company entered into a Sponsor Services Agreement with PSP Investments, pursuant to which the Company will provide certain mutually agreed services to PSP Investments and its affiliates with respect to the administration of the joint ownership of the project companies that PSP Investments invests in alongside the Company pursuant to the PSP Investments Joint Venture Agreement in exchange for certain fees set forth in the Sponsor Services Agreement. Related party fee amounts recorded during 2018 and 2017 were immaterial.

Segment Reporting

Segment Reporting	12 Months Ended
	Dec. 31, 2018
Segment Reporting [Abstract]
Segment Reporting	Segment Reporting The Company defines its operating segments to reflect the manner in which the Company's chief operating decision maker, the chief executive officer, evaluates performance and allocates resources in managing the business. The Company evaluates its operations in two reportable segments: (i) the operating business segment, which is comprised of the portfolio of renewable energy power projects and (ii) the development investment, which consists of the Company's investment in Pattern Development. The operating business segment is engaged in the sale of energy from the power projects. The development investment segment develops and sells renewable energy projects and consists solely of the Company's proportional share of its investment in Pattern Development. Corporate, other and eliminations includes operating companies that provide services to the Company's renewable energy power projects, various Pattern Energy Group LP subsidiaries, and Pattern Development and its equity losses in Pattern Development, and is presented to reconcile to the consolidated financial statements. The chief operating decision maker evaluates segment performance based on segment Adjusted EBITDA (Earnings Before Interest, Taxes, Depreciation and Amortization). The Company defines Adjusted EBITDA as net income (loss) before net interest expense, income taxes, and depreciation, amortization and accretion, including its proportionate share of net income (loss) before interest expense, income taxes, and depreciation, amortization and accretion of unconsolidated investments. Adjusted EBITDA also excludes the effect of certain mark-to-market adjustments, gain or loss related to acquisitions, divestitures, or refinancing transactions, adjustments from unconsolidated investments, and infrequent items not related to normal or ongoing operations. In calculating Adjusted EBITDA, the Company excludes mark-to-market adjustments to the value of the Company's derivatives because the Company believes that it is useful for investors to understand, as a supplement to net income (loss) and other traditional measures of operating results, the results of the Company's operations without regard to periodic, and sometimes material, fluctuations in the market value of such assets or liabilities. Prior to 2018, the Company had one reportable segment. The development investment segment was acquired in July 2017 and had insignificant operations in 2017. As such, comparative periods are not material or meaningful. Segment information for the year ended December 31, 2018 is presented in the table below. For the Year Ended December 31, 2018 (in millions) Operating Business Development Investment (1) Corporate, Other and Eliminations Reconciling Amounts (2) Consolidated Total revenue $ 475 $ 39 $ 8 $ (39 ) $ 483 Depreciation, amortization and accretion $ 247 $ — $ 3 $ — $ 250 Impairment expense $ — $ 11 $ 7 $ (11 ) $ 7 Operating income (loss) $ 45 $ (33 ) $ (43 ) $ 33 $ 2 Earnings (loss) in unconsolidated investments (3) $ 41 $ 1 $ (40 ) $ (1 ) $ 1 Interest expense $ 63 $ 1 $ 46 $ (1 ) $ 109 Income tax provision $ 11 $ 1 $ 21 $ (1 ) $ 32 Net income (loss) $ (38 ) $ (35 ) $ (31 ) $ 35 $ (69 ) Adjusted EBITDA $ 391 $ (22 ) $ (19 ) $ 22 Capital expenditures $ (175 ) $ (61 ) $ (6 ) $ 61 $ (181 ) As of December 31, 2018 Property, plant and equipment, net $ 4,054 $ 2 $ 65 $ (2 ) $ 4,119 Unconsolidated investments $ 228 $ 10 $ 42 $ (10 ) $ 270 Total assets $ 8,990 $ 187 $ (3,696 ) $ (187 ) $ 5,294 (1) Amounts represent the Company's proportionate share in Pattern Development. (2) The Company accounts for its investment in Pattern Development under the equity method. Therefore, the reconciling amounts are presented to eliminate Pattern Development and to reconcile to the consolidated totals. (3) Included in Corporate, Other and Eliminations is a $35 million loss related to the Company's portion of the loss of Pattern Development and the elimination of intra entity profits of approximately $5 million . Reconciliation of segment Adjusted EBITDA to the Company's consolidated net loss for the year ended December 31, 2018 is as follows: (in millions) Year ended December 31, 2018 Operating Business Adjusted EBITDA $ 391 Development Investment Adjusted EBITDA (22 ) Corporate, Other and Eliminations Adjusted EBITDA (19 ) Reconciling Amounts Adjusted EBITDA 22 Less, proportionate share from unconsolidated investments Interest expense, net of interest income (38 ) Income tax provision (1 ) Depreciation, amortization and accretion (35 ) Gain on derivatives 1 Unrealized loss derivatives (5 ) Early extinguishment of debt (6 ) Impairment expense (7 ) Other (2 ) Gain on asset sales 71 Interest expense, net of interest income (107 ) Depreciation, amortization and accretion (280 ) Net loss before income tax (37 ) Income tax provision (32 ) Net loss (69 )

Selected Quarterly Financial Da

Selected Quarterly Financial Data (Unaudited)	12 Months Ended
	Dec. 31, 2018
Quarterly Financial Information Disclosure [Abstract]
Selected Quarterly Financial Data (Unaudited)	Selected Quarterly Financial Data (Unaudited) The following tables summarize the Company’s unaudited quarterly consolidated statements of operations for each of the eight quarters in the two year period ended December 31, 2018 . The quarterly consolidated statements of operations data were prepared on a basis consistent with the audited consolidated financial statements included in this Annual Report on Form 10-K. Quarterly financial data in millions, except per share data: Three months ended December 31, September 30, June 30, March 31, 2018 2018 2018 2018 Revenue $ 113 $ 118 $ 140 $ 112 Gross profit (loss) $ (14 ) $ 20 $ 44 $ 14 Net loss $ (22 ) $ (32 ) $ (2 ) $ (13 ) Net loss attributable to noncontrolling interests (1) $ (9 ) $ (19 ) $ (34 ) $ (149 ) Net income (loss) attributable to Pattern Energy $ (13 ) $ (13 ) $ 32 $ 136 Earnings (loss) per share Basic $ (0.15 ) $ (0.13 ) $ 0.34 $ 1.39 Diluted $ (0.15 ) $ (0.13 ) $ 0.34 $ 1.32 Cash dividends declared per Class A common share $ 0.4220 $ 0.4220 $ 0.4220 $ 0.4220 (1) As discussed in Note 16. Stockholders' Equity , for the three months ended March 31, 2018, included in net loss attributable to noncontrolling interests is a one-time adjustment of $150 million as a result of the decrease in the federal corporate income tax rate. Three months ended December 31, September 30, June 30, March 31, 2017 2017 2017 2017 Revenue $ 110 $ 92 $ 108 $ 101 Gross profit (loss) $ 16 $ (2 ) $ 21 $ 28 Net income (loss) $ (22 ) $ (48 ) $ (15 ) $ 3 Net loss attributable to noncontrolling interests $ (14 ) $ (18 ) $ (29 ) $ (3 ) Net income (loss) attributable to Pattern Energy $ (8 ) $ (30 ) $ 14 $ 6 Basic and diluted earnings (loss) per share—Class A common stock $ (0.08 ) $ (0.34 ) $ 0.16 $ 0.06 Cash dividends declared per Class A common share $ 0.4220 $ 0.4200 $ 0.4180 $ 0.4138

Subsequent Events

Subsequent Events	12 Months Ended
	Dec. 31, 2018
Subsequent Events [Abstract]
Subsequent Events	Subsequent Events On January 29, 2019, PG&E filed for protection under Chapter 11 of the U.S. Bankruptcy Code. Hatchet Ridge, a 101 MW wind project, sells all of its output to PG&E through 2025 under a long-term PSA. As of December 31, 2018, Hatchet Ridge had approximately $138 million of net long-lived assets. The Company has also assessed and determined that Hatchet Ridge's long-lived assets are not impaired as of December 31, 2018. The Company is monitoring the bankruptcy proceedings for any changes in circumstances that would indicate the carrying amount of the net long-lived assets of Hatchet Ridge may not be recoverable. On February 22, 2019 , the Company approved a dividend for the first quarter 2019, payable on April 30, 2019 , to holders of record on March 29, 2019 , in the amount of $0.4220 per Class A share, which represents $1.688 on an annualized basis.

Schedule I-Condensed Parent-Com

Schedule I-Condensed Parent-Company Financial Statements	12 Months Ended
	Dec. 31, 2018
Condensed Financial Information of Parent Company Only Disclosure [Abstract]
Schedule I-Condensed Parent-Company Financial Statements	Pattern Energy Group Inc. Condensed Financial Information of Parent Balance Sheets (In millions of U.S. dollars, except share and par value data) December 31, 2018 December 31, 2017 Assets Current assets: Cash and cash equivalents $ 3 $ 9 Derivative assets, current 4 — Other current assets 17 26 Total current assets 24 35 Property, plant and equipment, net 2 4 Investments in subsidiaries 1,415 1,404 Investments in unconsolidated subsidiaries 270 311 Derivative assets 1 — Intangible assets, net 1 1 Other assets 1 1 Total assets $ 1,714 $ 1,756 Liabilities and equity Current liabilities: Accounts payable and other accrued liabilities $ 13 $ 12 Accrued interest 13 13 Dividend payable 42 41 Derivative liabilities, current — 3 Contingent liabilities, current 29 — Other current liabilities 3 9 Total current liabilities 100 78 Long-term debt, net of financing costs of $7 and $9 as of December 31, 2018 and 2017, respectively 560 553 Other long-term liabilities 7 32 Total liabilities 667 663 Equity: Class A common stock, $0.01 par value per share: 500,000,000 shares authorized; 98,051,629 and 97,860,048 shares outstanding as of December 31, 2018 and December 31, 2017, respectively 1 1 Additional paid-in capital 1,103 1,207 Accumulated income (loss) — (85 ) Accumulated other comprehensive loss (52 ) (26 ) Treasury stock, at cost; 223,040 and 157,812 shares of Class A common stock as of December 31, 2018 and 2017, respectively (5 ) (4 ) Total equity 1,047 1,093 Total liabilities and equity $ 1,714 $ 1,756 Statements of Operations and Comprehensive Income (Loss) (In millions of U.S. dollars) Year ended December 31, 2018 2017 2016 Revenue $ — $ — $ — Expenses 35 34 34 Operating loss (35 ) (34 ) (34 ) Other income (expense): Interest expense (37 ) (35 ) (15 ) Equity in earnings from subsidiaries 203 14 3 Equity in earnings from unconsolidated subsidiaries, net 1 41 30 Gain (loss) on undesignated derivatives, net 10 (7 ) (1 ) Other income (expense), net (1 ) (1 ) — Total other income (expense), net 176 12 17 Net income (loss) before income tax 141 (22 ) (17 ) Tax provision (benefit) — (4 ) — Net income (loss) 141 (18 ) (17 ) Other comprehensive income (loss): Proportionate share of subsidiaries' other comprehensive income (loss), net of tax benefit (provision) of $2, $(5) and less than $(1), respectively (27 ) 23 5 Proportionate share of affiliates' other comprehensive income (loss) activity, net of tax provision of less than $(1), $(5) and $(2), respectively 1 13 6 Total other comprehensive income (loss), net of tax (26 ) 36 11 Comprehensive income (loss) $ 115 $ 18 $ (6 ) Condensed Financial Information of Parent Condensed Statements of Cash Flows (In millions of U.S. dollars) Year ended December 31, 2018 2017 2016 Operating activities Net income (loss) $ 141 $ (18 ) $ (17 ) Adjustments to reconcile net loss to net cash provided by (used in) operating activities: Depreciation, amortization and accretion 11 7 6 Amortization of financing costs Amortization of debt discount Deferred taxes — 3 — Intraperiod tax allocation — (3 ) — (Gain) loss on derivatives (10 ) 5 3 Stock-based compensation 5 5 5 Equity in earnings from subsidiaries (203 ) (14 ) (3 ) Equity in earnings from unconsolidated investments, net (1 ) (41 ) (30 ) Other reconciling items 3 — (1 ) Changes in operating assets and liabilities: Other current assets — (20 ) (2 ) Accounts payable and other accrued liabilities — 3 2 Other current liabilities 29 8 — Long-term liabilities (28 ) 1 4 Related party receivable/payable 2 — — Accrued interest payable — 8 — Net cash used in operating activities (51 ) (56 ) (33 ) Investing activities Capital expenditures (3 ) — (4 ) Distributions received from subsidiaries 818 372 308 Contribution to subsidiaries (490 ) (682 ) (450 ) Investment in Pattern Development (115 ) (69 ) — Other assets 2 (1 ) (1 ) Net cash provided by (used in) investing activities 212 (380 ) (147 ) Financing activities Proceeds from public offering, net of issuance costs — 237 286 Proceeds from issuance of senior notes, net of issuance costs — 343 — Repurchase of shares for employee tax withholding (1 ) — — Dividends paid (166 ) (145 ) (120 ) Other financing activities — (2 ) (1 ) Net cash provided by (used in) financing activities (167 ) 433 165 Net change in cash, cash equivalents and restricted cash (6 ) (3 ) (15 ) Cash, cash equivalents and restricted cash at beginning of period 9 12 27 Cash, cash equivalents and restricted cash at end of period $ 3 $ 9 $ 12 Supplemental disclosures Cash payments for interest expense $ 30 $ 20 $ 9 Schedule of non-cash activities Change in property, plant and equipment (5 ) — — Non-cash increase in additional paid-in capital $ — $ (2 ) $ — Summary of Significant Accounting Policies Basis of Presentation The condensed, standalone financial statements of Pattern Energy Group Inc. (parent company) have been presented in accordance with Rule 12-04, Schedule I of Regulation S-X as the restricted net assets of the subsidiaries of the parent company exceed 25% of the consolidated net assets of the parent company and its subsidiaries. The condensed parent company financial statements have been prepared in accordance with United States generally accepted accounting principles and should be read in conjunction with the parent company’s consolidated financial statements and the accompanying notes thereto. Reconciliation of Cash and Cash Equivalents and Restricted Cash as presented on the Statements of Cash Flows (in millions) Year ended December 31, 2018 2017 2016 Cash and cash equivalents $ 3 $ 9 $ 12 Investments For purposes of these financial statements, the parent company’s wholly owned and majority owned subsidiaries are recorded based on its proportionate share of the subsidiaries’ assets. The parent company’s share of net income of its unconsolidated subsidiaries is included in income using the equity method. Debt 2024 Unsecured Senior Notes In January 2017, the Company issued unsecured senior notes with an aggregate principal amount of $350 million (the 2024 Notes). Net proceeds to the Company were approximately $345 million , after deducting the initial purchasers’ discount, commissions and transaction expenses. The 2024 Notes bear interest at a rate of 5.875% per year, payable semiannually in arrears on February 1 and August 1, beginning on August 1, 2017 and maturing on February 1, 2024, unless repurchased or redeemed at an earlier date. The 2024 Notes are guaranteed on a senior unsecured basis by Pattern US Finance Company, one of the Company's subsidiaries. Convertible Senior Notes due 2020 In July 2015, the Company issued $225 million aggregate principal amount of 4.00% convertible senior notes due 2020 (2020 Notes). The 2020 Notes bear interest at a rate of 4.00% per year, payable semiannually in arrears on January 15 and July 15 of each year, beginning on January 15, 2016. The 2020 Notes will mature on July 15, 2020. The 2020 Notes were sold in a private placement. Upon conversion, the Company may, at its discretion, pay cash, shares of the Company’s Class A common stock, or a combination of cash and stock. The 2020 Notes are set at an initial conversation rate of 35.4925 shares of Class A common stock per $1,000 principal amount of 2020 Notes, which is equivalent to an initial conversion price of approximately $28.175 per share of Class A common stock. The conversion rate is subject to adjustment in some events (including, but not limited to, certain cash dividends made to holders of the Company's Class A common stock which exceed the initial dividend threshold of $0.363 per quarter per share). The conversion rate would be adjusted to offset the effect of the portion of the dividend in excess of $0.363 , provided that the adjustment would result a change of at least 1% in the then effective conversion rate. During the year ended December 31, 2017, the conversion rate increased to 35.8997 shares of Class A common stock per $1,000 principal amount of 2020 Notes. The conversion rate will not be adjusted for any accrued and unpaid interest. The 2020 Notes are not redeemable prior to maturity. The 2020 Notes are guaranteed on a senior unsecured basis by a subsidiary of the Company and are general unsecured obligations of the Company. The obligations rank senior in rights of payment to the Company’s subordinated debt, equal in right of payment to the Company’s unsubordinated debt and effectively junior in right of payment to any of the Company’s secured indebtedness to the extent of the value of the assets securing such indebtedness. The following table presents a summary of the equity and liability components of the 2020 Notes (in millions): December 31, 2018 2017 Principal $ 225 $ 225 Less: Unamortized debt discount (8 ) (13 ) Unamortized financing costs (2 ) (3 ) Carrying value of convertible senior notes $ 215 $ 209 Carrying value of the equity component (1) $ 24 $ 24 (1) Included in the consolidated balance sheets as additional paid-in capital, net of $1 million in equity issuance costs. Commitments and Contingencies Operating Leases (in millions) 2019 2020 2021 2022 2023 Thereafter Total Operating leases $ 7 $ 7 $ 8 $ 7 $ 8 $ 30 $ 67 The Company has entered into lease agreements for office facilities in Houston, Texas and San Francisco, California. The Houston, Texas lease expires in April 2027. In March 2018, the Company entered into an operating lease for its new corporate headquarters in San Francisco, California. Total operating lease payments are approximately $35 million over the term of the lease which expires in December 2028.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2018
Accounting Policies [Abstract]
Basis of Presentation and Principles of Consolidation	Basis of Presentation and Principles of Consolidation The accompanying consolidated financial statements have been prepared in accordance with the accounting principles generally accepted in the United States (U.S. GAAP). They include the results of wholly-owned and partially-owned subsidiaries in which the Company has a controlling interest with all significant intercompany accounts and transactions eliminated.
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, disclosures of contingent assets and liabilities at the date of the financial statements, and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates, and such differences may be material to the consolidated financial statements.
Out-of-Period Adjustment	Out-of-Period Adjustment During the year ended December 31, 2018, the Company identified a $1 million error in tax expense related to the recognition of net operating loss carryforwards in its Chilean entity. The Company concluded the error was not material to any previously reported period and is not material to the year ended December 31, 2018. The Company recorded the error as an out-of-period adjustment in the year ended December 31, 2018.
Cash and Cash Equivalents	Cash and Cash Equivalents Cash and cash equivalents consist of cash in banks and highly liquid investments with original maturities of three months or less.
Restricted Cash	Restricted Cash Restricted cash consists of cash balances which are restricted as to withdrawal or usage and includes cash to collateralize bank letters of credit related primarily to transmission interconnection rights, power sale agreements (PSA) and for certain reserves required under the Company’s loan agreements.
Funds Deposited by Counterparty	Counterparty Collateral and Collateral Liability As a result of a counterparty's credit rating downgrade, the Company received collateral related to an energy derivative agreement, as discussed in Note 12 , Derivative Instruments . The Company does not have the right to pledge, invest, or use the collateral for general corporate purposes. As of December 31, 2018 , the Company has recorded a current asset of approximately $6 million to counterparty collateral and a current liability of approximately $6 million to counterparty collateral liability representing the collateral received and corresponding obligation to return the collateral, respectively.
Trade Receivables	Trade Receivables The Company’s trade receivables are generated by selling energy and renewable energy credits primarily to creditworthy utilities and large commercial companies. The Company believes that all amounts are collectible and an allowance for doubtful accounts is not required as of December 31, 2018 and 2017 . Although PG&E and PREPA, offtakers for Hatchet Ridge and Santa Isabel, respectively, have filed for reorganization and debt restructuring, the Company has assessed and determined that trade receivables at Hatchet Ridge and Santa Isabel were not impaired as of December 31, 2018.
Major Construction Advances	Major Construction Advances Major construction advances represent advances to (i) suppliers for the manufacture of wind turbines, transmission lines, and solar panels in accordance with component equipment supply agreements and (ii) builders in accordance with plant construction contracts. These construction advances are reclassified to construction in progress when the Company takes legal title to the equipment.
Derivatives	Derivatives The Company may enter into interest rate swaps, interest rate caps, forwards and other agreements to manage its interest rate, electricity price and foreign exchange rate risk. The Company recognizes its derivative instruments as assets or liabilities at fair value in the consolidated balance sheets, unless the derivative instruments qualify for the "normal purchase normal sale" (NPNS) scope exception to derivative accounting. Contracts used in normal business operations that are settled by physical delivery, among other criteria, are eligible for and may be designated as NPNS. NPNS contracts do not meet the definition of derivatives, and therefore, contracts associated with the sale of energy are recognized as electricity sales when revenue recognition criteria are met and contracts associated with the production of electricity are recognized as project expense when incurred on the consolidated statements of operations. The Company does not have contracts subject to master netting agreements with counterparties, as such assets and liabilities are presented gross on the consolidated balance sheets. Accounting for changes in the fair value of a derivative instrument depends on whether it has been designated as part of a hedging relationship and on the type of hedging relationship. For derivative instruments that qualify and are designated as cash flow hedges, the change in unrealized losses on cash flow hedges, net of tax is reported as a component of other comprehensive income (loss) (OCI), and is reclassified into earnings in the same period or periods during which the hedged transaction affects earnings. The ineffective portion of change in fair value is recorded as a component of net income (loss) on the consolidated statements of operations. The Company discontinues hedge accounting for its cash flow hedges prospectively when it has determined that the hedging relationship has materially changed since its inception or when the hedging instrument is no longer considered highly effective at offsetting the hedged risk. If the hedged transaction is no longer probable of occurring, any gain or loss previously deferred in OCI will be immediately recognized into earnings. If hedge accounting is discontinued for any other reason, any previously deferred gain or loss will remain in OCI and amortized into earnings as the hedged transaction affects future earnings. For undesignated derivative instruments, the change in fair value is reported as a component of net income (loss) on the consolidated statements of operations.
Fair Value of Financial Instruments	Fair Value of Financial Instruments Accounting Standards Codification (ASC) 820, Fair Value Measurement , defines fair value as the price at which an asset could be exchanged or a liability transferred in an orderly transaction between knowledgeable, willing parties in the principal or most advantageous market for the asset or liability. Where available, fair value is based on observable market prices or derived from such prices. Where observable prices or inputs are not available, valuation models are applied which may involve some level of management estimation and judgment, the degree of which is dependent on the price transparency for the instruments or market and the instruments’ complexity. See Note 14 , Fair Value Measurement .
Deferred Financing Costs	Deferred Financing Costs Financing costs incurred with securing a construction loan are recorded in the Company’s consolidated balance sheets as an offset to the construction loan and amortized over the contractual life of the loan to construction in progress using the effective interest method. Financing costs incurred with securing a term loan are recorded in the Company’s consolidated balance sheets as an offset to the term loan and amortized to interest expense in the Company’s consolidated statements of operations over the contractual life of the loan using the effective interest method. If the term loan has not been drawn on, financing costs incurred with securing the term loan are recorded in the Company’s consolidated balance sheets as an asset. Financing costs related to a revolving credit facility or a letter of credit facility are recorded in the Company’s consolidated balance sheets as an asset and amortized to interest expense in the Company’s consolidated statements of operations on a straight-line basis over the contractual term of the arrangement.
Construction in Progress	Construction in Progress Construction in progress represents the accumulation of project development costs and construction costs, including the costs incurred for the purchase of major equipment such as turbines for which the Company has taken legal title, civil engineering, electrical and other related costs. Other capitalized costs include reclassified deferred development costs, amortization of intangible assets, amortization of deferred financing costs, capitalized interest and other costs required to place a project into commercial operation. Deferred development costs represent the accumulated costs of initial permitting, environmental reviews, land rights and obligations and preliminary design and engineering work. The Company expenses all project development costs until a project is determined to be technically feasible and likely to achieve commercial success, typically when a power purchase agreement has been negotiated. The Company begins capitalizing deferred development costs as a component of construction in progress on the date the project commences construction. Once the project achieves commercial operation, the Company reclassifies the amounts recorded in construction in progress to property, plant and equipment.
Property, Plant and Equipment	Property, Plant and Equipment Property, plant and equipment represents the costs of completed and operational projects transferred from construction in progress, as well as other costs incurred for purchasing assets such as land, computer equipment and software, furniture and fixtures, leasehold improvements and other equipment. Property, plant and equipment are stated at cost, less accumulated depreciation. Depreciation is calculated using the straight-line method over the respective assets’ useful lives. Wind farms for which construction began before 2011 are depreciated over 20 years and wind farms for which construction began after 2011 are depreciated over 25 to 30 years . Solar facilities are depreciated over 25 years . Transmission assets are depreciated over 50 years . The remaining assets are depreciated over two to five years. Improvements to property, plant and equipment deemed to extend the useful economic life of an asset are capitalized. Repair and maintenance costs are expensed as incurred.
Intangible Assets and Intangible Liabilities	Intangible Assets and Intangible Liabilities Long-lived intangible assets and intangible liabilities primarily include power purchase agreements (PPAs), land easements, land options, tax savings and mining rights. PPAs obtained through acquisitions are valued as of the acquisition date and the difference between the contract price and the estimated fair value is recorded as an intangible asset or liability. If the contract price is higher than the estimated fair value, the Company will recognize an intangible asset. If the contract price is lower than the estimated fair value, the Company will recognize an intangible liability. Land easements, land options and mining rights are recognized at the carryover basis from the seller as their carrying costs approximate fair value. The Company generally amortizes PPAs using the straight-line method over the remaining term of the related PPA. The Company amortizes land easements, land options, tax savings and mining rights using the straight-line method over the term of their estimated useful lives, which represents the term of the land easements, land option, tax savings and mining rights agreements, ranging from approximately 9 to 50 years . The Company periodically evaluates whether events or changes in circumstances have occurred that indicate the carrying amount of long-lived intangible assets may not be recoverable, or information indicates that impairment may exist.
Goodwill	Goodwill The Company records goodwill when the purchase price of an acquired business exceeds its fair value as of the acquisition date. Goodwill is not amortized, but is subject to an assessment for impairment at least annually in the fourth quarter or more frequently if events occur or circumstances change that will more likely than not reduce the fair value of the reporting unit below its carrying amount.
Accounting for Impairment of Long-Lived Assets and Accounting for Re-powering	The Company may first assess goodwill for qualitative factors to determine whether it is necessary to perform a quantitative impairment test. The qualitative analysis considers entity-specific and macroeconomic factors and their potential impact on the key assumptions used in the determination of the fair value of the reporting unit. A quantitative impairment test is performed if the results of the qualitative assessment indicate that it is more likely than not that the fair value of the reporting unit is less than its carrying value, or if a qualitative assessment is not performed. Quantitative tests compare the fair value of the asset to its carrying value. Accounting for Re-powering The Company's commitment to a plan to re-power a project represents the decision to abandon the existing long-lived asset. The decision to abandon a long-lived asset is viewed as an indicator of impairment, and as such a recoverability test is required. If the recoverability test indicates that the carrying value is not recoverable, the fair value of the existing asset is compared to its net carrying value. If the fair value of the asset is less than its net carrying value, an impairment expense for the difference is recorded. The remaining useful life of the existing asset represents the period between the date the Company is committed to a plan to abandon the asset and the removal date. Due to the change in useful life, the Company will revise the estimated future cash flows of the asset retirement obligation. As a result, the Company will accelerate depreciation expense and accretion expense. In 2018, the Company committed to a plan to repower its Gulf Wind facility, as such the Company performed a recoverability test. The Company passed the recoverability test and did not recognize an impairment. However, beginning in the fourth quarter of 2018, the Company revised the depreciable life for the portion of the Gulf Wind facility it expects to abandon to approximately 15 months . As of December 31, 2018, the Company's construction start date is not finalized and, as such the future depreciation rate may be adjusted as the timing of construction becomes more certain.
Variable Interest Entities	Variable Interest Entities VIEs are entities that do not qualify for a scope exception from the variable interest model and are therefore subject to consolidation under the variable interest model. An entity is considered to be a VIE if (1) the entity does not have enough equity to finance its own activities without additional support, (2) the entity’s at-risk equity holders lack the characteristics of a controlling financial interest, or (3) the entity is structured with non-substantive voting rights. ASC 810, Consolidation , defines the criteria for determining the existence of VIEs and provides guidance for consolidation. The Company consolidates VIEs where the Company is the primary beneficiary. The primary beneficiary of a VIE is the party that has the power to direct the activities that most significantly impact the performance of the entity and the obligation to absorb losses or the right to receive benefits that could potentially be significant to the entity. To the extent the entity does not meet the definition of a VIE, the ASC 810 guidance for voting interest entities (VOEs) is applied. The usual condition for a controlling financial interest, and therefore consolidation by the Company, is ownership of a majority voting interest of a corporation or a majority of kick-out rights for a limited partnership. To the extent the entity is not consolidated under the VIE or VOE models, the Company uses the equity method of accounting. These amounts are included in unconsolidated investments in the consolidated balance sheets.
Acquisitions and Business Combinations	Acquisitions Accounting Standards Update (ASU) 2017-01, Clarifying the Definition of a Business (ASU 2017-01) provides a screen test to determine when a set of assets and activities should not be considered a business. Under ASU 2017-01, the Company will perform an initial screening test as of the acquisition date that, if met, results in the conclusion that the set is not a business. If the initial screening test is not met, the Company evaluates whether the set is a business based on whether there are inputs and a substantive process in place. The definition of a business impacts whether the Company consolidates an acquisition under business combination guidance or asset acquisition guidance. When the Company's acquisition is recognized as an equity method investment, the definition of a business impacts whether equity method goodwill can be recognized. Business Combinations The Company accounts for its business combinations by recognizing the identifiable assets acquired, the liabilities assumed, and any non-controlling interest in the acquiree at the acquisition date. The purchase is accounted for using the acquisition method, and the fair value of purchase consideration is allocated to the tangible and intangible assets acquired and the liabilities assumed, based on their estimated fair values. Contingent consideration is also recognized and measured at fair value as of the acquisition date. The excess, if any, of the fair value of the purchase consideration over the fair values of the identifiable net assets is recorded as goodwill. Conversely, the excess, if any, of the net fair values of the identifiable net assets over the fair value of the purchase consideration is recorded as a gain. Such valuations require management to make significant estimates and assumptions, especially with respect to intangible assets. These estimates and assumptions are inherently uncertain, and as a result, actual results may differ from estimates. Significant estimates include, but are not limited to, future expected cash flows, useful lives and discount rates. During the measurement period, which is up to one year from the acquisition date, we may record adjustments to the assets acquired and liabilities assumed, with a corresponding offset to either goodwill or gain, depending on whether the fair value of purchase consideration is in excess of or less than net assets acquired. Upon the conclusion of the measurement period, any subsequent adjustments are recorded to earnings. Transaction costs associated with business combinations are expensed as incurred.
Asset Acquisitions	Asset Acquisitions When the Company acquires assets and liabilities that do not constitute a business or a VIE of which the Company is the primary beneficiary , the fair value of the purchase consideration, including the transaction costs of the asset acquisition, is assumed to be equal to the fair value of the net assets acquired. The purchase consideration, including the transaction costs, is allocated to the individual assets and liabilities assumed based on their relative fair values. Contingent consideration associated with the acquisition is generally recognized only when the contingency is resolved. No goodwill is recognized in an asset acquisition. When the Company acquires assets and liabilities that do not constitute a business but meet the definition of a VIE of which the Company is the primary beneficiary, the purchase is accounted for using the acquisition method described above for business combinations, except that no goodwill is recognized. To the extent that there is difference between the purchase consideration and the VIE's identifiable assets and liabilities recorded and measured at fair value, the difference is recognized as a gain or loss.
Equity Method Investments	Equity Method Investments When the Company acquires a noncontrolling interest in an entity where it is not the primary beneficiary, does not control any of the ongoing activities of the entity, and does not meet consolidation requirements of ASC 810 and ASU 2015-02 , Consolidation (Topic 810): Amendments to the Consolidation Analysis, the investment is initially recognized as an equity method investment at cost. Any difference between the cost of an investment and the amount of underlying equity in net assets of an investee are considered basis differences. Basis differences related to the property, plant and equipment are amortized over the estimated economic useful life of the underlying long-lived assets while basis differences related to the PPA are amortized over the remaining term of the PPA. Transactions costs associated with equity method investments are included in the investment. When the Company receives distributions in excess of the carrying value of its investment, and the Company is not liable for the obligations of the investee nor otherwise committed to provide financial support, the Company recognizes such excess distributions as equity method earnings in the period the distributions occur. Additionally, when the Company's carrying value in an unconsolidated investment is zero and the Company is not liable for the obligations of the investee nor otherwise committed to provide financial support, the Company will not recognize equity in earnings (losses) or equity in other comprehensive income of unconsolidated investments. When the investee subsequently reports income, the Company does not record its share of such income until it equals the amount of distributions in excess of the carrying value that were previously recognized in income and previously unrecognized losses. During the years ended December 31, 2018, 2017 and 2016, the Company had no such obligations, commitments or requirements to provide additional funding for unconsolidated investments with carrying values below zero during such years. Profits or losses related to intra-entity transactions with an equity method investment are eliminated until realized by the Company. As a result, equity income or loss reported on the Company's income statement for certain unconsolidated investments may differ from a mathematical calculation of net income or loss attributable to the Company's equity interest based upon the factor of its equity interest and the net income or loss attributable to equity owners as shown on investee companies' income statements. To the extent that cumulative comprehensive income exceeds cumulative distributions received, the Company records the distribution as distributions from unconsolidated investments on the Company's consolidated statements of cash flows within operating cash flows. All other distributions are recorded as distributions from unconsolidated investments on the Company's consolidated statements of cash flows within investing activities.
Noncontrolling Interests	Noncontrolling Interests Noncontrolling interests represent the portion of the Company’s net income (loss), net assets and comprehensive income (loss) that is not allocable to the Company and is calculated based on ownership percentage, for applicable projects. For the noncontrolling interests in the Company’s Panhandle 1, Panhandle 2, Post Rock, Logan's Gap, Amazon Wind, Broadview Holdings, and Stillwater, the Company has determined that the operating partnership agreements do not allocate economic benefits pro rata to its two classes of investors and the appropriate methodology for calculating the noncontrolling interest balance that reflects the substantive profit sharing arrangement is a balance sheet approach using the hypothetical liquidation at book value (HLBV) method. Under the HLBV method, the amounts reported as noncontrolling interest in the consolidated balance sheets and consolidated statements of operations represent the amounts the third party would hypothetically receive at each balance sheet reporting date under the liquidation provisions of the operating partnership agreement assuming the net assets of the projects were liquidated at recorded amounts determined in accordance with U.S. GAAP and distributed to the investors. The noncontrolling interest in the results of operations and comprehensive income (loss) is determined as the difference in noncontrolling interests in the consolidated balance sheets at the start and end of each reporting period, after taking into account any capital transactions between the projects and the third party. The noncontrolling interest balances in the projects are reported as a component of equity in the consolidated balance sheets.
Asset Retirement Obligation	Asset Retirement Obligation The Company records asset retirement obligations (AROs) for the estimated costs of decommissioning turbines, removing above-ground installations and restoring sites, at the time when a contractual decommissioning obligation is incurred. AROs represent the present value of the expected costs and timing of the related decommissioning activities. The ARO assets and liabilities are recorded in property, plant and equipment and other long-term liabilities, respectively, in the consolidated balance sheets. The Company records accretion expense, which represents the increase in the asset retirement obligations, over the remaining or operational life of the associated wind project. Accretion expense is recorded as cost of revenue in the consolidated statements of operations using accretion rates based on credit adjusted risk-free interest rates. Changes resulting from revisions to the timing or amount of the original estimate of cash flows are recognized as an increase or a decrease in the asset retirement cost, or income when the asset retirement cost is depleted.
Contingent Liabilities	Contingent Liabilities Contingent obligations that are acquired through business combinations are initially recorded at fair value on the date of acquisition while contingent obligations that are acquired through asset acquisitions are recorded when the contingency is resolved. Subsequent to the initial recognition of contingent obligations accounted for as a business combination, the Company accounts for these contingent obligations in a systematic and rational method in accordance with ASC 450, Contingencies. The Company’s contingent liabilities related to turbine availability warranties with turbine manufacturers and turbine availability guarantees associated with long-term turbine service arrangements are reported at net realizable value. Pursuant to these warranties and guarantees, if a turbine operates at less than minimum availability during the warranty or guarantee period, the manufacturer or service provider is obligated to pay, as liquidated damages, an amount for each percent that the turbine operates below the minimum availability threshold at the end of the warranty period. However, the Company does not recognize liquidated damages that remain contingent until the end of the warranty period. In addition, pursuant to certain of these warranties and guarantees, if a turbine operates at more than a specified availability during the warranty or guarantee period, the Company has an obligation to pay a bonus to the turbine manufacturer or service provider at the end of the warranty period. The Company records contingent liabilities at each reporting period associated with these bonuses expected to be paid at the end of the warranty period.
Concentrations of Credit Risk	Concentrations of Credit Risk Financial instruments that potentially subject the Company to concentrations of credit risk consist primarily of cash and cash equivalents, trade receivables, reimbursable interconnection costs and derivative instruments. The Company’s cash and cash equivalents are with high quality institutions. The Company has exposure to credit risk to the extent cash and cash equivalent balances, including restricted cash, exceed amounts covered by federal deposit insurance; however, the Company believes that its credit risk is immaterial. In addition, reimbursable interconnection costs are with large creditworthy utility companies and the Company’s derivative instruments are placed with counterparties that are creditworthy institutions. The Company generally does not require collateral.
Revenue Recognition	Revenue Recognition Beginning in 2018, the Company adopted ASC 606 Revenue Recognition (ASC 606). See Note 3, Revenue, regarding our revenue recognition policy . The Company sells electricity and related RECs under the terms of PSAs, PPAs or at market prices. Revenue is recognized based upon the amount of electricity delivered at rates specified under the contracts, or at market prices for spot market transactions, assuming all other revenue recognition criteria are met. When renewable energy credits are sold as a separate component, revenue is recognized at the time title to the energy credits is transferred to the buyer. Depending on the terms of the PSA, the Company may account for the contracts as operating leases pursuant to ASC 840, Leases (ASC 840), or derivative instruments pursuant to ASC 815, Derivatives and Hedging (ASC 815). In considering ASC 840, it was determined that certain of the Company's PPAs are operating leases. ASC 840 requires minimum lease payments to be recognized over the term of the lease and contingent rents to be recorded when the achievement of the contingency becomes probable. All energy sales under the PPAs, which are considered leases, are contingent rent due to the inherent uncertainty and variability associated with a fuel source (i.e., wind or solar) that is outside the control of the parties to the PPA . None of the operating leases have minimum lease payments; therefore, revenue from these contracts and any related renewable energy attributes are recognized as electricity sales when delivered. Contingent rents for the years ending December 31, 2018, 2017 and 2016 were approximately $381 million , $317 million and $262 million , respectively. Contracts that meet the NPNS scope exception to derivative accounting are accounted for under the accrual method, where revenues are recorded in the period they are earned. Energy derivative instruments that reduce exposure to changes in commodity prices may allow the Company to lock in a fixed price per megawatt hour (MWh) for a specified amount of annual electricity generation over the life of the swap contract. Monthly settlement amounts under energy hedges are accounted for as energy derivative settlements in the consolidated statements of operations. Changes in the fair value of energy hedges are recorded in electricity sales in the consolidated statements of operations. The Company recognizes revenue for warranty settlements in other revenue upon resolution of outstanding contingencies. Any cash receipts for amounts subject to future adjustment or repayment are deferred in other liabilities until the final settlement amount is considered fixed and determina
Cost of Revenue	Cost of Revenue The Company’s cost of revenue is comprised of direct costs of operating and maintaining its wind and solar project facilities, including labor, turbine service arrangements, land lease royalties, depreciation, accretion of asset retirement obligations, property taxes and insurance. These costs are recognized by the Company in the period in which they are incurred.
Stock-Based Compensation	Stock-Based Compensation The Company accounts for stock-based compensation related to stock options granted to employees by estimating the fair value of the stock-based awards using the Black-Scholes option-pricing model. The Black-Scholes option pricing model includes assumptions regarding dividend yields, expected volatility, expected option term, and risk-free interest rates. Expense is recognized by amortizing the fair value of the stock options granted using a straight-line method over the applicable vesting period. The Company estimates expected volatility based on the historical volatility of comparable publicly traded companies for a period that is equal to the expected term of the options. The risk-free interest rate is based on the U.S. treasury yield curve in effect at the time of grant for a period commensurate with the estimated expected term of the stock option. The expected term of options granted is derived using the "simplified" method as allowed under the provisions of the ASC 718, Compensation—Stock Compensation, and represents the period of time that options granted are expected to be outstanding. The Company accounts for stock-based compensation related to restricted stock award grants and restricted stock unit grants by amortizing the fair value of the restricted stock award grants, which is the grant date market price, over the applicable vesting period. For certain restricted stock award grants, the Company measures the fair value at the grant date using a Monte Carlo simulation model and amortizes the fair value over the longer of the requisite period or performance period. The Monte Carlo simulation model includes assumptions regarding dividend yields, expected volatility, risk-free interest rates and initial total shareholder return (TSR) performance. The Company accounts for forfeitures as they occur. The forfeitures are not material. Stock-based compensation expense is recorded as a component of general and administrative expenses in the Company’s consolidated statements of operations.
Income Taxes	Income Taxes The Company accounts for income taxes under the asset and liability method, which requires the recognition of deferred tax assets and liabilities for the expected future tax consequences of events that have been included in the financial statements. Under this method, deferred tax assets and liabilities are determined on the basis of the differences between the financial statement and tax basis of assets and liabilities using enacted tax rates in effect for the year in which the differences are expected to reverse. The effect of a change in tax rates on deferred tax assets and liabilities is recognized in income in the period that includes the enactment date. The Company recognizes deferred tax assets to the extent that it believes these assets are more likely than not to be realized. In making such a determination, the Company considers all available positive and negative evidence, including future reversals of existing taxable temporary differences, projected future taxable income, tax-planning and results of recent operations. If the Company determines that it would be able to realize its deferred tax assets in the future in excess of their net recorded amount, it would make an adjustment to the deferred tax asset valuation allowance, which would reduce the provision for income taxes. The Company records uncertain tax positions in accordance with ASC 740, Income Taxes, on the basis of a two-step process whereby (1) it determines whether it is more likely than not that the tax positions will be sustained on the basis of the technical merits of the position and (2) for those tax positions that meet the more-likely-than-not recognition threshold, it recognizes the largest amount of tax benefit that is more than 50% likely to be realized upon ultimate settlement with the related tax authority. The Company has a policy to classify interest and penalties associated with uncertain tax positions together with the related liability, and the expenses incurred related to such accruals, if any, are included in the provision for income taxes.
Comprehensive Income (Loss)	Comprehensive Income (Loss) Comprehensive income (loss) consists of net income (loss) and other comprehensive income (loss), net of tax. Other comprehensive income (loss), net of tax included in accumulated other comprehensive income (loss) in the consolidated statements of stockholders’ equity, is comprised primarily of changes in foreign currency translation adjustments and the effective portion of changes in the fair value of derivatives designated as cash flow hedges.
Foreign Currency Translation	Foreign Currency Translation The assets and liabilities of foreign subsidiaries, where the local currency is the functional currency, are translated from their respective functional currencies into U.S. dollars at the rates in effect at the balance sheet date and revenue and expense amounts are translated at average rates during the period, with resulting foreign currency translation adjustments recorded in other comprehensive income (loss), net of tax, in the consolidated statements of stockholders’ equity and comprehensive income (loss). Where the U.S. dollar is the functional currency, re-measurement adjustments are recorded in other income (expense), net in the accompanying consolidated statements of operations.
Segment Data and Geographic Information	Segment data Operating segments are defined as components of a company about which separate financial information is available that is evaluated regularly by the chief operating decision maker in deciding how to allocate resources and in assessing performance. The Company’s chief operating decision maker is the chief executive officer. Based on the financial information presented to and reviewed by the chief operating decision maker in deciding how to allocate the resources and in assessing the Company’s performance, the Company has determined it has two reportable segments: (i) the operating business segment, which is comprised of the portfolio of renewable energy power projects and (ii) the development investment, which consists of the Company's investment in Pattern Development.
Recently Issued Accounting Standards	Recently Adopted Accounting Standards In August 2018, the Financial Accounting Standards Board (FASB) issued ASU 2018-15, Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract (ASU 2018-15), which amends alignment of the requirements for capitalizing implementation costs incurred in a hosting arrangement that is a service contract with the requirements for capitalizing implementation costs incurred to develop or obtain internal-use software (and hosting arrangements that include an internal use software license). The accounting for the service element of a hosting arrangement that is a service contract is not affected by these amendments. ASU 2018-15 is effective for fiscal years beginning after December 15, 2019, and interim periods within those fiscal years. Early adoption is permitted, including adoption in an interim period. The Company adopted ASU 2018-15 during the year ended December 31, 2018. The adoption did not have material impact on the Company's consolidated financial statements. In February 2018, the FASB issued ASU 2018-02 , Reclassification of Certain Tax Effects from Accumulated Other Comprehensive Income (ASU 2018-02), which allows a reclassification from Accumulated Other Comprehensive Income (AOCI) to retained earnings for the stranded tax effects resulting from the Tax Cuts and Jobs Act in December 2017 (Tax Act). The amount of the reclassification is calculated as the difference between the amount initially recorded to other comprehensive income (OCI) at the time of the previously enacted tax rate that remains in AOCI and the amount that would have been recorded using the newly enacted tax rate. The Company adopted ASU 2018-02 in its financial statements for the period ended December 31, 2018 and elected not to reclassify the stranded tax effects related to the Tax Act. Furthermore, the U.S. operations are in a net deferred tax asset position offset by a full valuation allowance. As a result, the adoption did not have an impact on the Company's consolidated financial statements. The Company’s accounting policy is to release stranded income tax effects from AOCI when the circumstances upon which the stranded tax effects are premised cease to exist. In February 2017, the FASB issued ASU 2017-05, Other Income-Gains and Losses from the Derecognition of Nonfinancial Assets (Subtopic 610-20): Clarifying the Scope of Asset Derecognition Guidance and Accounting for Partial Sales of Nonfinancial Assets (ASU 2017-05). This ASU is meant to clarify the scope of ASC Subtopic 610-20, Other Income-Gains and Losses from the Derecognition of Nonfinancial Assets and to add guidance for partial sales of nonfinancial assets. The Company adopted ASU 2017-05 as of January 1, 2018. The adoption did not have a material impact on the Company’s consolidated financial statements and related disclosures. In May 2014, the FASB issued ASU 2014-09, Revenue from Contracts with Customers (Topic 606), which supersedes the revenue recognition requirements in Topic 605 “Revenue Recognition” (Topic 605) and requires entities to recognize revenue when control of the promised goods or services is transferred to customers at an amount that reflects the consideration to which the entity expects to be entitled to in exchange for those goods or services. The Company adopted ASU 2014-09 as of January 1, 2018 using the modified retrospective transition method. The adoption did not have a material impact on the Company's consolidated financial statements, other than additional disclosures. See Note 3, Revenue for further details. Recently Issued Accounting Standards Not Yet Adopted In October 2018, the FASB issued ASU 2018-17, Consolidation (Topic 810): Targeted Improvements to Related Party Guidance for Variable Interest Entities (ASU 2018-17). ASU 2018-17 requires reporting entities to consider indirect interests held through related parties under common control on a proportional basis rather than as the equivalent of a direct interest in its entirety for determining whether a decision-making fee is a variable interest. The standard is effective for all entities for financial statements issued for fiscal years beginning after December 15, 2019, and interim periods within those fiscal years. Early adoption is permitted. Entities are required to apply the amendments in ASU 2018-17 retrospectively with a cumulative-effect adjustment to retained earnings at the beginning of the earliest period presented. The Company is currently evaluating this guidance to determine the impact it may have on its consolidated financial statements. In October 2018, the FASB issued ASU 2018-16, Derivatives and Hedging (Topic ASC 815): Inclusion of the Secured Overnight Financing Rate (SOFR) Overnight Index Swap (OIS) Rate as a Benchmark Interest Rate for Hedge Accounting Purposes (ASU 2018-16), which expands the list of U.S. benchmark interest rates permitted in the application of hedge accounting. Because of concerns about the sustainability of LIBOR, the Federal Reserve Board and the Federal Reserve Bank of New York (Fed) initiated an effort to introduce an alternative reference rate in the United States. The SOFR is calculated by the Fed based on the interest rates banks charge one another in the overnight market, typically called repurchase agreements, and because it is based on transactions in the open market, it is more reflective of market conditions than LIBOR, which relies on judgment. The provisions of ASU 2017-12 (discussed below) and ASU 2018-16 are effective for fiscal years beginning after December 15, 2018, including interim periods, with early adoption permitted. Initial adoption of ASU 2017-12 is required to be reported using a modified retrospective approach, with the exception of the presentation and disclosure requirements which are required to be applied prospectively. The Company is currently in the process of determining the impact of adoption of the provisions of ASU 2017-12 and ASU 2018-16. In August 2018, the FASB issued ASU 2018-13, Changes to the Disclosure Requirements for Fair Value Measurement (ASU 2018-13), which amends changes in unrealized gains and losses, the range and weighted average of significant unobservable inputs used to develop Level 3 fair value measurements, and the narrative description of measurement uncertainty which should be applied prospectively for only the most recent interim or annual period presented in the initial fiscal year of adoption. ASU 2018-13 is effective for annual periods beginning after December 15, 2019, including interim periods within those periods. Early application is permitted. The Company is currently assessing the impact of changes to the disclosure requirements for fair value measurement. In August 2017, the FASB issued ASU 2017-12, Targeted Improvements to Accounting for Hedging Activities (ASU 2017-12), which amends the presentation and disclosure requirements and changes how companies assess effectiveness. The amendments are intended to more closely align hedge accounting with companies’ risk management strategies, simplify the application of hedge accounting, and increase transparency as to the scope and results of hedging programs. ASU 2017-12 is effective for annual periods beginning after December 15, 2018, including interim periods within those periods. The Company adopted the standard on January 1, 2019. ASU 2017-12 requires a modified retrospective transition method in which the Company will recognize the cumulative effect of the change on the opening balance of each affected component of equity in the statement of financial position as of the date of adoption. While the Company continues to assess all potential impacts of the standard, the adoption is not expected to have a material impact on its future consolidated financial statements. In June 2016, the FASB issued ASU 2016-13, Financial Instruments —Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments (ASU 2016-13), which requires the measurement of all expected credit losses for financial assets including trade receivables held at the reporting date based on historical experience, current conditions, and reasonable and supportable forecasts. In November 2018, the FASB issued ASU 2018-19, Codification Improvements to Topic 326, Financial Instruments - Credit Losses , for the purposes of clarifying certain aspects of ASU 2016-13. ASU 2016-13 is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2019. The adoption of ASU 2016-13 is not expected to have a material impact on the Company's consolidated financial statements and related disclosures. In February 2016, the FASB issued ASU 2016-02, Leases (ASU 2016-02), as amended by subsequent ASUs, which requires lessees to recognize right-of-use assets and lease liabilities, for all leases, with the exception of short-term leases, at the commencement date of each lease. Under the new guidance, lessor accounting is largely unchanged. ASU 2016-02 simplifies the accounting for sale and leaseback transactions primarily because lessees must recognize lease assets and liabilities. The Company adopted the new standard effective January 1, 2019 using a modified retrospective method and will not restate comparative periods. As permitted under the transition guidance, the Company may carry forward the assessment of whether its contracts contain or are leases, its lease classification, initial direct costs and remaining lease terms. The Company may also elect the practical expedient related to land easements, allowing the Company to carry forward its accounting treatment for land easements on existing agreements as its intangible assets; however, the accounting for future land easements may not be accounted for as intangibles. The Company has lease agreements with lease and non-lease components and will elect not to separate them and treat them as a single lease component. The Company will make an accounting policy election whereby short-term leases with an initial term of 12 months or less will not be recorded on the consolidated balance sheets. The Company anticipates that certain PPAs will no longer be accounted for as leases. The adoption of ASU 2016-02 may have a material impact on the Company's consolidated balance sheets, primarily related to land and office leases. The Company does not expect this standard to have a material impact on its consolidated statements of operations.

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2018
Accounting Policies [Abstract]
Reconciliation Between BS and SCF for Cash Cash Equivalent and Restricted Cash	Reconciliation of Cash and Cash Equivalents and Restricted Cash as presented on the Statements of Cash Flows The following table provides a reconciliation of cash, cash equivalents, and restricted cash reported within the consolidated balance sheets that sum to the total of the same such amounts shown in the consolidated statements of cash flows (in millions): December 31, 2018 2017 2016 Cash and cash equivalents $ 101 $ 117 $ 84 Restricted cash - current 4 9 12 Restricted cash 18 12 13 Cash, cash equivalents and restricted cash shown in the consolidated statements of cash flows $ 123 $ 138 $ 109
Schedule of Percentages of Total Revenues and Related Maximum Amount of Credit Loss of Total Trade Receivables from Significant Customers	The table below presents significant customers who accounted for greater than 10% of total revenue, PREPA and PG&E for the years ended December 31, 2018 , 2017 and 2016 : Year ended December 31, 2018 2017 2016 Revenue Revenue Revenue Morgan Stanley Capital Group Inc. 7.2 % 9.1 % 10.9 % PG&E 5.3 % 6.8 % 8.5 % PREPA 4.1 % 4.2 % 6.0 % San Diego Gas & Electric 12.2 % 13.4 % 14.6 % Southern California Edison Company 11.9 % 5.8 % — %
Summary of Geographical Revenues and Assets	The table below provides information, by country, about the Company’s consolidated operations. Revenue is recorded in the country in which it is earned and assets are recorded in the country in which they are located (in millions): Revenue Property, Plant and Equipment, net Year ended December 31, December 31, 2018 2017 2016 2018 2017 United States $ 346 $ 315 $ 285 $ 3,124 $ 3,121 Canada 83 62 39 745 550 Japan 33 — — 250 — Chile (1) 21 34 30 — 294 Total $ 483 $ 411 $ 354 $ 4,119 $ 3,965 (1) The Company sold its interest in El Arrayán on August 20, 2018. See Note 4, Divested Operations .

Revenue (Tables)

Revenue (Tables)	12 Months Ended
	Dec. 31, 2018
Revenue from Contract with Customer [Abstract]
Disaggregation of Revenue	The following table presents the Company's total revenue recognized and, for revenue from contracts with customers, disaggregated by revenue sources (in millions): Year ended December 31, 2018 2017 (1) 2016 (1) Revenue from contracts with customers Electricity sales Electricity sales under PSA $ 74 $ 65 $ 69 Electricity sales to market 14 21 16 REC sales 7 7 5 Electricity sales from contracts with customers 95 93 90 Other revenue Related party management service fees 8 7 5 Other revenue from contracts with customers 8 7 5 Total revenue from contracts with customers 103 100 95 Other electricity sales (2) 369 309 257 Other revenue 11 2 2 Total revenue $ 483 $ 411 $ 354 (1) As noted above, prior period amounts have not been adjusted under the modified retrospective method. (2) Includes revenue from PSAs accounted for as leases and energy hedge contracts.
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction	The Company expects to recognize revenue under PSAs and related party management service fees in the following amounts related to fixed consideration associated with remaining performance obligations in each of the future periods noted as of December 31, 2018 (in millions): Amount 2019 $ 79 2020 66 2021 67 2022 67 2023 67 Thereafter 276 Total $ 622

Acquisitions (Tables)

Acquisitions (Tables)	12 Months Ended
	Dec. 31, 2018
Business Combinations [Abstract]
Schedule of Fair Value of Assets Acquired and Liabilities Assumed	The aggregate purchase prices of the acquisitions were allocated as follows (in millions): December 31, 2018 2017 Japan Acquisition (1) MSM (2) Stillwater (2) Broadview (1) Meikle (2) Purchase price Cash paid for acquisitions, net of cash and restricted cash acquired $ 158 $ 31 $ 111 $ 169 $ 58 Contingent consideration 106 — — 21 — $ 264 $ 31 $ 111 $ 190 $ 58 Allocation Property, plant and equipment, net $ 269 $ 270 $ 120 $ 628 $ 376 Construction in progress 179 — — — — Intangibles 103 — — 22 29 Goodwill 60 — — — — Other assets acquired 20 38 4 12 8 Debt (181 ) (196 ) — (51 ) (266 ) Deferred tax liabilities (65 ) — — — — Advanced lease revenue — (29 ) — — — Other liabilities assumed (110 ) (14 ) (13 ) (95 ) (24 ) Assets and liabilities assumed before noncontrolling interests 275 69 111 516 123 Less: noncontrolling interests (11 ) (38 ) — (326 ) (65 ) Total consideration allocated to acquired assets and liabilities $ 264 $ 31 $ 111 $ 190 $ 58 1) Business Combination 2) Asset Acquisition
Schedule of Supplemental Pro Forma Data	The unaudited pro forma data should not be considered representative of the Company’s future financial condition or results of operations. Year ended December 31, Unaudited pro forma data (in millions) 2018 2017 Pro forma total revenue $ 487 $ 435 Pro forma total expenses 556 520 Pro forma net loss (69 ) (85 ) Less: pro forma net loss attributable to noncontrolling interest (211 ) (65 ) Pro forma net income (loss) attributable to Pattern Energy $ 142 $ (20 ) The following table presents the amounts included in the consolidated statements of operations for the business combinations discussed above since their respective dates of acquisition: Year ended December 31, Unaudited data (in millions) 2018 2017 Total revenue $ 96 $ 33 Total expenses 105 50 Net loss (9 ) (17 ) Less: net loss attributable to noncontrolling interest (48 ) (17 ) Net income attributable to Pattern Energy $ 39 $ —

Intangible Assets and Liabili_2

Intangible Assets and Liabilities and Goodwill (Tables)	12 Months Ended
	Dec. 31, 2018
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of Major Components of Finite-Lived Intangible Assets and Liability	The following presents the major components of the long-lived intangible assets and liabilities (in millions): December 31, 2018 Weighted Average Remaining Life Gross Accumulated Amortization Net Intangible assets Power purchase agreement 15 $ 225 $ (31 ) $ 194 Industrial revenue bond tax savings 23 13 (1 ) 12 Other intangible assets 33 14 (1 ) 13 Total intangible assets $ 252 $ (33 ) $ 219 Intangible liabilities Power purchase agreement 14 60 (13 ) 47 Leasehold interest 22 9 — 9 Total intangible liabilities $ 69 $ (13 ) $ 56 December 31, 2017 Weighted Average Remaining Life Gross Accumulated Amortization Net Intangible assets Power purchase agreement 15 $ 127 $ (18 ) $ 109 Industrial revenue bond tax savings 24 13 — 13 Other intangible assets 34 15 (1 ) 14 Total intangible assets $ 155 $ (19 ) $ 136 Intangible liability Power purchase agreement 15 $ 60 $ (9 ) $ 51
Schedule of Estimated Future Amortization Expense	The following table presents estimated future amortization for the next five years related to intangible assets and liabilities. The sum of estimated future amortization in the following table may differ from intangible assets and liabilities balances due to rounding. Year ended December 31, Power Purchase Agreements, Net Industrial revenue bond tax savings Other Intangible Assets Leasehold Interest 2019 $ 10 $ 1 $ 1 $ — 2020 10 1 1 — 2021 10 1 1 — 2022 10 1 1 — 2023 10 1 1 — Thereafter 101 9 10 (7 )
Schedule of Goodwill	The following table presents a reconciliation of the beginning and ending carrying amounts of goodwill (in millions): Total Balances at December 31, 2017 $ — Net additions during the period 60 Foreign currency translation adjustment (2 ) Balances at December 31, 2018 $ 58

Property, Plant and Equipment (

Property, Plant and Equipment (Tables)	12 Months Ended
	Dec. 31, 2018
Property, Plant and Equipment [Abstract]
Schedule of Property, Plant and Equipment	The following presents the categories within property, plant and equipment (in millions): December 31, 2018 2017 Operating wind farms $ 4,972 $ 4,641 Transmission line 94 94 Furniture, fixtures and equipment 16 12 Subtotal 5,082 4,747 Less: accumulated depreciation (963 ) (782 ) Property, plant and equipment, net $ 4,119 $ 3,965

Variable Interest Entities (Tab

Variable Interest Entities (Tables)	12 Months Ended
	Dec. 31, 2018
Variable Interest Entities [Abstract]
Schedule of Variable Interest Entities	The following table summarizes the carrying amounts of major consolidated balance sheet items for consolidated VIEs as of December 31, 2018 and 2017 (in millions). All assets (excluding deferred financing costs, net and long-lived intangible assets, net) and liabilities included in the consolidated VIE presented below are (1) assets that can be used only to settle obligations of the VIE or (2) liabilities for which creditors do not have recourse to the general credit of the primary beneficiary. December 31, 2018 2017 Assets Current assets: Cash and cash equivalents $ 36 $ 33 Restricted cash 4 4 Trade receivables 13 13 Prepaid expenses 6 5 Other current assets 2 3 Total current assets 61 58 Restricted cash 3 3 Construction in progress 1 — Property, plant and equipment, net 2,156 1,985 Deferred financing costs, net 2 2 Intangible assets, net 12 12 Other assets 12 13 Total assets $ 2,247 $ 2,073 Liabilities Current liabilities: Accounts payable and other accrued liabilities $ 27 $ 27 Accrued construction costs 1 1 Current portion of long-term debt, net 4 — Other current liabilities 5 5 Total current liabilities 37 33 Long-term debt, net 149 — Intangible liability, net 48 51 Asset retirement obligations 57 22 Other long-term liabilities 36 25 Deferred revenue 26 — Total liabilities $ 353 $ 131

Unconsolidated Investments (Tab

Unconsolidated Investments (Tables)	12 Months Ended
	Dec. 31, 2018
Equity Method Investments and Joint Ventures [Abstract]
Schedule of Unconsolidated Investments	The Company's unconsolidated investments consist of the following for the periods presented below (in millions): December 31, Percentage of Ownership December 31, 2018 2017 2018 2017 South Kent $ 5 $ 6 50.0 % 50.0 % Grand 5 7 45.0 % 45.0 % K2 — 103 — % 33.3 % Armow 116 133 50.0 % 50.0 % Pattern Development 144 62 29.3 % 20.9 % Unconsolidated investments $ 270 $ 311

Debt (Tables)

Debt (Tables)	12 Months Ended
	Dec. 31, 2018
Debt Disclosure [Abstract]
Schedule of Long Term Debt	The Company’s debt consists of the following for periods presented below (in millions): December 31, 2018 December 31, Contractual Interest Rate Effective Interest Rate 2018 2017 Maturity Corporate-level Corporate Revolving Credit Facility $ 198 $ — varies (1 ) 4.01 % November 2022 2020 Notes 225 225 4.00 % 6.60 % July 2020 2024 Notes 350 350 5.88 % 5.88 % February 2024 Project-level Fixed interest rate El Arrayán EKF term loan (6) — 99 — % — % N/A Santa Isabel term loan 100 104 4.57 % 4.57 % September 2033 Mont Sainte Marguerite-Med Term Loan 62 — 3.97 % 3.97 % December 2029 Mont Sainte Marguerite-Long Term loan 93 — 5.04 % 5.04 % June 2042 Variable interest rate Japan Credit Facility 25 — varies (5 ) 1.82 % August 2022 Ocotillo commercial term loan 281 289 4.30 % 4.01 % (3 ) June 2033 El Arrayán commercial term loan (6) — 90 — % — % N/A Spring Valley term loan (6) — 126 — % — % N/A St. Joseph term loan (2) 152 172 4.06 % 4.11 % (3 ) November 2033 Western Interconnect term loan (7) 52 54 4.19 % 4.21 % (3 ) May 2034 Meikle term loan (2) 239 267 3.81 % 3.97 % (3 ) May 2024 Futtsu term loan 75 — 1.07 % 1.85 % (3 ) December 2033 Ohorayama term loan 93 — 0.87 % 0.88 % (3 ) February 2036 Tsugaru Construction Loan 131 — 0.72 % 0.72 % (3 ) March 2038 Tsugaru Holdings Loan Agreement 59 — 3.07 % 3.07 % July 2022 Imputed interest rate Hatchet Ridge financing lease obligation 180 192 1.43 % 1.43 % December 2032 2,315 1,968 Unamortized premium/discount, net (4) (11 ) (14 ) Unamortized financing costs (21 ) (23 ) Total debt, net $ 2,283 $ 1,931 As reflected on the consolidated balance sheets Revolving credit facility, current $ 198 $ — Revolving credit facility 25 — Current portion of long-term debt, net of financing costs 56 52 Long term debt, net of financing costs 2,004 1,879 Total debt, net $ 2,283 $ 1,931 (1) Refer to Corporate Revolving Credit Facility for interest rate details. (2) The amortization for the St. Joseph term loan and the Meikle term loan are through September 2036 and December 2038, respectively, which differs from the stated maturity date of such loans due to prepayment requirements. (3) Includes impact of interest rate swaps. See Note 12 , Derivative Instruments , for discussion of interest rate swaps. (4) The discount relates to the 2020 Notes and MSM term loans. (5) Refer to Japan Credit Facility for interest rate details. (6) The El Arrayán EKF term loan and El Arrayán commercial term loan were included as part of the Chilean Sale on August 20, 2018. The Spring Valley term loan was prepaid in full on December 31, 2018. (7) Refer to "Project Debt - Western Interconnect" below for additional borrowing details.
Summary of Principal Payments Due under Long Term Debt	The following are principal payments, excluding deferred financing costs, due under the Company's debt as of December 31, 2018 for the following years (in millions): Amount 2019 $ 254 2020 288 2021 74 2022 154 2023 73 Thereafter 1,472 Total $ 2,315
Schedule of Reconciliation of Interest Expense	Interest and commitment fees incurred and interest expense for debt consisted of the following (in millions): Year ended December 31, 2018 2017 2016 Corporate-level interest and commitment fees incurred $ 38 $ 34 $ 18 Project-level interest and commitment fees incurred 64 55 48 Capitalized interest, commitment fees, and letter of credit fees (4 ) — — Amortization of debt discount/premium, net 5 5 4 Amortization of financing costs 6 8 7 Other interest — — 1 Interest expense $ 109 $ 102 $ 78
Convertible Debt	The following table presents a summary of the equity and liability components of the 2020 Notes (in millions): December 31, 2018 2017 Principal $ 225 $ 225 Less: Unamortized debt discount (8 ) (13 ) Unamortized financing costs (2 ) (3 ) Carrying value of convertible senior notes $ 215 $ 209 Carrying value of the equity component (1) $ 24 $ 24 (1) Included in the consolidated balance sheets as additional paid-in capital, net of $1 million in equity issuance costs.

Asset Retirement Obligation (Ta

Asset Retirement Obligation (Tables)	12 Months Ended
	Dec. 31, 2018
Asset Retirement Obligation Disclosure [Abstract]
Reconciliation of Beginning and Ending Aggregate Carrying Amounts of Asset Retirement Obligations	The following table presents a reconciliation of the beginning and ending aggregate carrying amounts of asset retirement obligations (in millions): December 31, 2018 2017 Beginning asset retirement obligations $ 57 $ 45 Net additions during the year (1) 67 9 Foreign currency translation adjustment (2 ) — Divested operations (3 ) — Revision in estimated cash flows 85 — Accretion expense 5 3 Ending asset retirement obligations $ 209 $ 57 (1) Reflects non-cash additions due to acquisitions and construction during the year ended December 31, 2018. See Note 5 , Acquisitions , for discussion of acquisitions.

Derivative Instruments (Tables)

Derivative Instruments (Tables)	12 Months Ended
	Dec. 31, 2018
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Schedule of Derivative Instruments in Statement of Financial Position, Fair Value	The following tables present the fair values of the Company's derivative instruments on a gross basis as reflected on the Company’s consolidated balance sheets (in millions): December 31, 2018 Derivative Assets Derivative Liabilities Current Long-Term Current Long-Term Fair Value of Designated Derivatives: Interest rate swaps $ — $ 3 $ 2 $ 25 Fair Value of Undesignated Derivatives: Interest rate swaps — — — 4 Energy derivative 7 — — — Foreign currency forward contracts 6 6 — 2 Congestion revenue rights 1 — — — Total Fair Value $ 14 $ 9 $ 2 $ 31 December 31, 2017 Derivative Assets Derivative Liabilities Current Long-Term Current Long-Term Fair Value of Designated Derivatives: Interest rate swaps $ — $ 2 $ 4 $ 18 Fair Value of Undesignated Derivatives: Interest rate swaps — — 1 3 Energy derivative 19 8 — — Foreign currency forward contracts — — 3 — Total Fair Value $ 19 $ 10 $ 8 $ 21
Schedule of Notional Amounts of Outstanding Derivative Positions	The following table summarizes the notional amounts of the Company's outstanding derivative instruments (in millions except for MWh): December 31, Unit of Measure 2018 2017 Designated Derivative Instruments Interest rate swaps USD $ 319 $ 253 Interest rate swaps CAD $ 721 $ 736 Interest rate swaps JPY ¥ 55,675 ¥ — Undesignated Derivative Instruments Interest rate swaps USD $ 138 $ 85 Energy derivative MWh 193,252 697,471 Foreign currency forward contracts CAD $ 106 $ 128 Foreign currency forward contracts JPY ¥ 11,589 ¥ — Congestion revenue rights MWh 505 —
Derivative Instruments, Gain (Loss)	The following table presents the pre-tax effect of the hedging instruments designated as cash flow recognized in accumulated other comprehensive loss, amounts reclassified to earnings for the following periods, as well as, amounts recognized in interest expense (in millions): Year ended December 31, Description 2018 2017 2016 Losses recognized in accumulated OCI Effective portion of change in fair value $ (6 ) $ (2 ) $ (8 ) Losses reclassified from accumulated OCI into: Interest expense Derivative settlements $ (5 ) $ (10 ) $ (8 ) Loss on derivatives De-designation of derivatives $ — $ (2 ) $ —
Schedule of Other Derivatives Not Designated as Hedging Instruments, Statements of Financial Performance and Financial Position, Location	The following table presents gains and losses on derivatives not designated as hedges (in millions): Year ended December 31, Derivative Type Financial Statement Line Item 2018 2017 2016 Interest rate derivatives Gain (loss) on derivatives $ — $ (1 ) $ (2 ) Energy derivative Electricity sales $ (3 ) $ 5 $ (1 ) Foreign currency forward contracts Gain (loss) on derivatives $ 16 $ (7 ) $ (1 ) Foreign currency option contract Gain (loss) on derivatives $ 1 $ — $ —

Accumulated Other Comprehensi_2

Accumulated Other Comprehensive Loss (Tables)	12 Months Ended
	Dec. 31, 2018
Equity [Abstract]
Summary of Accumulated Other Comprehensive (Loss) Income	The following table summarizes changes in the accumulated other comprehensive loss balance, net of tax, by component (in millions): Foreign Currency Effective Portion of Change in Fair Value of Derivatives Proportionate Share of Equity Investee's OCI Total Balances at December 31, 2015 $ (48 ) $ (14 ) $ (12 ) $ (74 ) Other comprehensive income (loss) before reclassifications 5 (7 ) 1 (1 ) Amounts reclassified from accumulated other comprehensive loss — 8 4 12 Net current period other comprehensive loss 5 1 5 11 Balances at December 31, 2016 (43 ) (13 ) (7 ) (63 ) Other comprehensive income (loss) before reclassifications 15 (3 ) 6 18 Amounts reclassified from accumulated other comprehensive loss — 11 8 19 Net current period other comprehensive loss 15 8 14 37 Balances at December 31, 2017 (28 ) (5 ) 7 (26 ) Other comprehensive loss before reclassifications (37 ) (4 ) (3 ) (44 ) Amounts reclassified from accumulated other comprehensive loss — 5 5 10 Net current period other comprehensive income (loss) (37 ) 1 2 (34 ) Balances at December 31, 2018 $ (65 ) $ (4 ) $ 9 $ (60 )

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	12 Months Ended
	Dec. 31, 2018
Fair Value Disclosures [Abstract]
Financial Assets and (Liabilities) Required Fair Value Measurement on Recurring Basis	The Company’s financial assets and liabilities which require fair value measurement on a recurring basis are classified within the fair value hierarchy as follows (in millions): December 31, 2018 Level 1 Level 2 Level 3 Total Assets Interest rate swaps $ — $ 3 $ — $ 3 Energy derivative — — 7 7 Foreign currency forward contracts — 12 — 12 Congestion revenue rights — — 1 1 $ — $ 15 $ 8 $ 23 Liabilities Interest rate swaps $ — $ 31 $ — $ 31 Foreign currency forward contracts — 2 — 2 Contingent consideration — — 130 130 $ — $ 33 $ 130 $ 163 December 31, 2017 Level 1 Level 2 Level 3 Total Assets Interest rate swaps $ — $ 2 $ — $ 2 Energy derivative — — 27 27 Foreign currency forward contracts — — — — $ — $ 2 $ 27 $ 29 Liabilities Interest rate swaps $ — $ 26 $ — $ 26 Foreign currency forward contracts — 3 — 3 Contingent consideration — — 22 22 $ — $ 29 $ 22 $ 51
Reconciliation of Derivative Assets Measured at Fair Value	The following table presents a reconciliation of the energy derivative contract measured at fair value on a recurring basis using significant unobservable inputs (in millions): Energy Derivative 2018 2017 Balance, beginning of year $ 27 $ 41 Total gain (loss) included in electricity sales (3 ) 5 Settlements (17 ) (19 ) Balance, end of year $ 7 $ 27
Reconciliation of Contingent Consideration Measured at Fair Value	The following table presents a reconciliation of the contingent consideration liability measured at fair value on a recurring basis using significant unobservable inputs (in millions): Contingent Consideration Liability 2018 2017 Balance, beginning of year $ 22 $ — Purchases 106 21 Total loss included in other income (expense), net 5 1 Settlements (3 ) — Balance, end of year $ 130 $ 22
Schedule of Valuation Techniques and Significant Unobservable Inputs Used in Level 3 Fair Value Measurements	The valuation techniques and significant unobservable inputs used in recurring Level 3 fair value measurements were as follows (in millions, for fair value): December 31, 2018 Fair Value Valuation Technique Significant Unobservable Inputs Range Energy derivative $7 Discounted cash flow Forward electricity prices $20.02 - $32.58 (1) Discount rate 2.80% - 2.81% Broadview contingent consideration $25 Discounted cash flow Discount rate 4.0% - 8.0% Annual energy production loss 0.70% Tsugaru contingent consideration $105 Discounted cash flow Deferred purchase price $109 - $128 million Discount rate 6.90% Congestion revenue rights $1 Market approach Auction prices $2.48 - $8.23 (1) December 31, 2017 Fair Value Valuation Technique Significant Unobservable Inputs Range Energy derivative $27 Discounted cash flow Forward electricity prices $14.44 - $71.45 (1) Discount rate 1.69% - 1.96% Broadview contingent consideration $22 Discounted cash flow Discount rate 4.0% - 8.0% Annual energy production loss 1.0% (1) Represents price per MWh
Carrying Amounts and Fair Values of Company's Financial Liabilities	The following table presents the carrying amount and fair value and the fair value hierarchy of the Company’s financial liabilities that are not measured at fair value in the consolidated balance sheets, but for which fair value is disclosed (in millions): Fair Value As reflected on the balance sheet Level 1 Level 2 Level 3 Total December 31, 2018 Total debt, net $ 2,283 $ — $ 2,240 $ — $ 2,240 December 31, 2017 Total debt, net $ 1,931 $ — $ 1,938 $ — $ 1,938

Income Taxes Income Taxes (Tabl

Income Taxes Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Components of Provision for Income Taxes	The following table presents significant components of the provision for income taxes (in millions): Year ended December 31, 2018 2017 2016 Current: Federal $ — $ — $ — State — — — Foreign 16 — — Total current expense 16 — — Deferred: Federal — (3 ) — State — — — Foreign 16 15 9 Total deferred expense 16 12 9 Total provision for income taxes $ 32 $ 12 $ 9
Domestic and Foreign Components of Net Income (Loss) Before Income Tax (Benefit) Expense	The following table presents the domestic and foreign components of net loss before income tax provision (in millions): Year ended December 31, 2018 2017 2016 U.S. $ (158 ) $ (119 ) $ (71 ) Foreign 121 49 28 Total $ (37 ) $ (70 ) $ (43 )
Reconciliation of Statutory U.S Federal Income Tax Rate to Effective Tax Rate	The following table presents a reconciliation of the statutory U.S. federal income tax rate to the Company’s effective tax rate, as a percentage of income before taxes for the following periods: Year ended December 31, 2018 2017 2016 Computed tax at statutory rate 21.0 % 35.0 % 35.0 % Adjustment for income in non-taxable entities allocable to noncontrolling interests (125.2 )% (32.6 )% (25.6 )% Foreign rate differential Tax rate differential on pre-tax book income (16.1 )% 6.4 % 0.7 % Dual taxpaying entities outside basis difference (78.5 )% (23.0 )% (17.6 )% Local tax on branch profits/(losses)—Puerto Rico (0.1 )% 0.1 % — % Permanent book/tax differences (domestic only) 0.5 % (0.1 )% (0.2 )% Valuation allowance change 38.9 % 47.7 % (18.8 )% Subpart F income (7.9 )% (3.5 )% — % Capital gain exclusion - sale of partnership interest 24.7 % — % — % Contingent consideration accretion (4.9 )% — % — % Impairment 1.4 % — % — % Tax credits 61.7 % 31.6 % 7.6 % Effect of U.S. tax rate change under Tax Cuts and Jobs Act — % (78.1 )% — % Other (2.5 )% (0.1 )% (0.9 )% Effective income tax rate (87.0 )% (16.6 )% (19.8 )%
Components of Deferred Tax Assets and Deferred Tax Liabilities	ignificant components of the Company’s deferred tax assets and liabilities are as follows (in millions): Year ended December 31, 2018 2017 Deferred tax assets: Accruals and prepaids $ 3 $ 3 Basis difference in derivatives 3 — Hatchet Ridge financing 17 17 Asset retirement obligation 32 6 Unrealized loss on derivatives — 2 Net operating loss carryforwards 230 274 Foreign currency translation adjustments 2 3 Other deferred tax assets 12 2 Tax credits 118 42 Total gross deferred tax assets 417 349 Less: Valuation allowance (175 ) (141 ) Total gross deferred tax assets net of valuation allowance $ 242 $ 208 Deferred tax liabilities: Property, plant and equipment $ (215 ) $ (189 ) Intangibles (24 ) — Partnership interest (108 ) (65 ) Deferred interest, commitment fees and financing costs (2 ) (2 ) Unrealized gain on derivatives (2 ) — Basis difference in subsidiaries (2 ) (1 ) Other deferred tax liabilities (1 ) (1 ) Total gross deferred tax liabilities (354 ) (258 ) Total net deferred tax assets/(liabilities) $ (112 ) $ (50 )

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	12 Months Ended
	Dec. 31, 2018
Equity [Abstract]
Noncontrolling Interests By Project	The following table presents the balances for noncontrolling interests by project (in millions). December 31, 2018 2017 El Arrayán (1) $ — $ 32 Logan's Gap 132 171 Panhandle 1 131 175 Panhandle 2 176 208 Post Rock 116 160 Amazon Wind 101 134 Broadview Project 257 308 Futtsu 10 — Meikle 57 66 MSM 37 — Stillwater 95 — Noncontrolling interests $ 1,112 $ 1,254 (1) Noncontrolling interest of El Arrayán was derecognized as a result of the sale of the Company's operation in Chile.
Schedule of Noncontrolling Interest	The following table presents the components of total noncontrolling interests as reported in stockholders’ equity in the consolidated balance sheets (in millions). Capital Accumulated Income (Loss) Accumulated Other Comprehensive Income (Loss) Noncontrolling Interests Balances at December 31, 2015 $ 972 $ (27 ) $ (1 ) $ 944 Distributions to noncontrolling interests (18 ) — — (18 ) Net loss — (35 ) — (35 ) Other comprehensive income, net of tax — — — — Balances at December 31, 2016 954 (62 ) (1 ) 891 Acquisitions 390 — — 390 Distributions to noncontrolling interests (20 ) — — (20 ) Partial sale of subsidiary 56 — — 56 Net loss — (64 ) — (64 ) Other comprehensive income, net of tax — — 1 1 Balances at December 31, 2017 $ 1,380 $ (126 ) $ — $ 1,254 Acquisitions 49 — — 49 Contribution from noncontrolling interests 98 — — 98 Distributions to noncontrolling interests (38 ) — — (38 ) Sale of subsidiaries (37 ) 5 — (32 ) Net loss (1) — (211 ) — (211 ) Other comprehensive loss, net of tax — — (8 ) (8 ) Balances at December 31, 2018 $ 1,452 $ (332 ) $ (8 ) $ 1,112 (1) On December 22, 2017, the Tax Act was signed into law, which enacted major changes to the U.S. federal income tax laws, including a permanent reduction in the U.S. federal corporate income tax rate from 35% to 21%, effective January 1, 2018. Reduction in the corporate income tax rate resulted in a one-time reduction in the noncontrolling interests attributable to partners in its tax equity partnerships. As part of the liquidation waterfall, the Company allocated significantly lower portions of the hypothetical liquidation proceeds to compensate certain noncontrolling interest investors for tax gains on the hypothetical sale calculated at the lowered rate of 21% as compared to the rate of 35% that was previously utilized. For the year ended December 31, 2018, included in net loss attributable to noncontrolling interests is a one-time adjustment of $150 million as a result of the decrease in the federal corporate income tax rate.

Equity Incentive Award Plan (Ta

Equity Incentive Award Plan (Tables)	12 Months Ended
	Dec. 31, 2018
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Schedule of Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Grant Date Intrinsic Value	A summary of option activity under the employee share option plan as of December 31, 2018 , and changes during the year then ended is presented below. Shares Weighted-Average Exercise Price Weighted Average Remaining Contractual Life Aggregate Intrinsic Value (in millions) Outstanding at December 31, 2017 411,323 $ 22.00 Forfeited or expired (29,169 ) $ 22.00 Outstanding at December 31, 2018 382,154 4.7 — Exercisable at December 31, 2018 382,154 4.7 —
Schedule of Share-based Payment Award, TSR-RSAs, Valuation Assumptions	The Company measures the fair value of these restricted stock awards at the grant date using a Monte Carlo simulation model and amortizes the fair value over the longer of the requisite period or performance period. The Company estimates expected volatility based on the actual volatility of the Company's daily closing share price since listing on September 27, 2013 and the historical volatility of comparable publicly traded companies for a period that is equal to the performance period. The risk-free interest rate is based on the yield on U.S. government bonds for a period commensurate with the performance period. The assumptions used to estimate the fair value of TSR-RSAs are as follows: Years ended December 31, 2018 2017 2016 Expected stock price volatility (1) 32% 34% 35% Expected dividend yield N/A N/A N/A Risk-free interest rate 2.38% 1.60% 1.11% Expected performance period in years (2) 2.8 2.8 2.8 (1) The expected volatility was estimated using the historical volatility derived from the Company's Class A common stock. (2) The expected performance period was estimated based on the length of the remaining performance period from the grant date.
Summary of Restricted Stock Awards Activity	The following table summarizes RSA activity under the 2013 Plan for the year ended December 31, 2018 : Shares Weighted-Average Grant-Date Nonvested at December 31, 2017 110,579 $ 19.26 Granted 138,817 $ 18.67 Vested (127,268) $ 19.03 Nonvested at December 31, 2018 122,128 $ 18.84 The following table summarizes TSR-RSAs activity under the 2013 Plan for the year ended December 31, 2018 : Shares Weighted-Average Grant-Date Nonvested at December 31, 2017 218,877 $ 25.07 Granted 97,610 $ 18.20 Vested (56,844 ) 39.16 Nonvested at December 31, 2018 259,643 $ 19.40

Earnings (Loss) Per Share (Tabl

Earnings (Loss) Per Share (Tables)	12 Months Ended
	Dec. 31, 2018
Earnings Per Share [Abstract]
Computations of Basic and Diluted Earnings (Loss) per Share	The computations for Class A basic and diluted earnings (loss) per share are as follows (in millions except share data): Year ended December 31, 2018 2017 2016 Numerator for basic and diluted earnings (loss) per share: Net income (loss) attributable to Pattern Energy $ 142 $ (18 ) $ (17 ) Less: earnings allocated to participating securities — — — Net income (loss) attributable to common stockholders $ 142 $ (18 ) $ (17 ) Denominator for earnings (loss) per share: Weighted average number of shares: Class A common stock - basic 97,456,407 89,179,343 79,382,388 Add dilutive effect of: Restricted stock awards 193,910 — — Restricted stock units 1,184 — — Class A common stock - diluted 97,651,501 89,179,343 79,382,388 Earnings (loss) per share: Class A common stock: Basic $ 1.45 $ (0.20 ) $ (0.22 ) Diluted $ 1.45 $ (0.20 ) $ (0.22 ) Dividends declared per Class A common share $ 1.69 $ 1.67 $ 1.58

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2017
Commitments and Contingencies Disclosure [Abstract]
Contractual Obligation, Fiscal Year Maturity Schedule	The following table summarizes estimates of future commitments related to the various agreements that the Company has entered into as of December 31, 2018 (in millions): 2019 2020 2021 2022 2023 Thereafter Total Transmission service agreements (1) $ 24 $ 24 $ 24 $ 24 $ 24 $ 495 $ 615 Operating leases (2) 22 21 22 21 22 352 460 Service and maintenance agreements 32 30 30 27 26 68 213 Construction and other commitments 192 155 4 3 3 34 391 Total commitments $ 270 $ 230 $ 80 $ 75 $ 75 $ 949 $ 1,679 (1) Future commitments under the transmission service agreements are based on current rates, which are subject to future changes. (2) Certain operating leases have adjustments for market provisions. Amounts in the above table represent the best estimates of future payments to be made under these leases.

Related Party Transactions (Tab

Related Party Transactions (Tables)	12 Months Ended
	Dec. 31, 2018
Related Party Transactions [Abstract]
Related Party Transactions Receivable and Payable	The table below presents amounts due from and to related parties as included in the consolidated balance sheets for the following periods (in millions): December 31, 2018 2018 2017 Other current assets $ 7 $ 13 Total due from related parties $ 7 $ 13 Other current liabilities $ 9 $ 11 Contingent liabilities, current 25 — Contingent liabilities 105 21 Total due to related parties $ 139 $ 32
Related Party Revenue and Expense Included in Combined Statement of Operations	The table below presents the revenue, reimbursement and (expenses) recognized for management services and under the MSA, as included in the statements of operations for the following periods (in millions): Years Ended December 31, Related Party Agreement Financial Statement Line Item 2018 2017 2016 Management fees Other revenue $ 9 $ 8 $ 6 Management fees Project expense $ 1 $ — $ — MSA reimbursement General and administrative $ 12 $ 12 $ 5 MSA costs Related party general and administrative expense $ (15 ) $ (14 ) $ (10 )
Related Party Transactions Purchase Agreements	During the years ended December 31, 2018 , and 2017, the Company consummated the following investment and acquisitions with Pattern Energy Group LP and Pattern Development which are further detailed in Note 5 , Acquisitions (in millions): Acquisitions from Pattern Development Companies Date of Acquisition Cash consideration net of acquired cash Debt Assumed Contingent Consideration Japan projects March 7, 2018 $ 158 $ 181 $ 106 MSM August 10, 2018 $ 31 $ 196 $ — Stillwater Wind LLC November 20, 2018 $ 17 $ — $ — Broadview Project April 21, 2017 $ 169 $ 51 $ 21 Meikle August 10, 2017 $ 58 $ 266 $ —

Segment Reporting (Tables)

Segment Reporting (Tables)	12 Months Ended
	Dec. 31, 2018
Segment Reporting [Abstract]
Schedule of Segment Reporting Information, by Segment	Segment information for the year ended December 31, 2018 is presented in the table below. For the Year Ended December 31, 2018 (in millions) Operating Business Development Investment (1) Corporate, Other and Eliminations Reconciling Amounts (2) Consolidated Total revenue $ 475 $ 39 $ 8 $ (39 ) $ 483 Depreciation, amortization and accretion $ 247 $ — $ 3 $ — $ 250 Impairment expense $ — $ 11 $ 7 $ (11 ) $ 7 Operating income (loss) $ 45 $ (33 ) $ (43 ) $ 33 $ 2 Earnings (loss) in unconsolidated investments (3) $ 41 $ 1 $ (40 ) $ (1 ) $ 1 Interest expense $ 63 $ 1 $ 46 $ (1 ) $ 109 Income tax provision $ 11 $ 1 $ 21 $ (1 ) $ 32 Net income (loss) $ (38 ) $ (35 ) $ (31 ) $ 35 $ (69 ) Adjusted EBITDA $ 391 $ (22 ) $ (19 ) $ 22 Capital expenditures $ (175 ) $ (61 ) $ (6 ) $ 61 $ (181 ) As of December 31, 2018 Property, plant and equipment, net $ 4,054 $ 2 $ 65 $ (2 ) $ 4,119 Unconsolidated investments $ 228 $ 10 $ 42 $ (10 ) $ 270 Total assets $ 8,990 $ 187 $ (3,696 ) $ (187 ) $ 5,294 (1) Amounts represent the Company's proportionate share in Pattern Development. (2) The Company accounts for its investment in Pattern Development under the equity method. Therefore, the reconciling amounts are presented to eliminate Pattern Development and to reconcile to the consolidated totals. (3) Included in Corporate, Other and Eliminations is a $35 million loss related to the Company's portion of the loss of Pattern Development and the elimination of intra entity profits of approximately $5 million .
Reconciliation of Operating Profit (Loss) from Segments to Consolidated	Reconciliation of segment Adjusted EBITDA to the Company's consolidated net loss for the year ended December 31, 2018 is as follows: (in millions) Year ended December 31, 2018 Operating Business Adjusted EBITDA $ 391 Development Investment Adjusted EBITDA (22 ) Corporate, Other and Eliminations Adjusted EBITDA (19 ) Reconciling Amounts Adjusted EBITDA 22 Less, proportionate share from unconsolidated investments Interest expense, net of interest income (38 ) Income tax provision (1 ) Depreciation, amortization and accretion (35 ) Gain on derivatives 1 Unrealized loss derivatives (5 ) Early extinguishment of debt (6 ) Impairment expense (7 ) Other (2 ) Gain on asset sales 71 Interest expense, net of interest income (107 ) Depreciation, amortization and accretion (280 ) Net loss before income tax (37 ) Income tax provision (32 ) Net loss (69 )

Selected Quarterly Financial _2

Selected Quarterly Financial Data (Unaudited) (Tables)	12 Months Ended
	Dec. 31, 2018
Quarterly Financial Information Disclosure [Abstract]
Quarterly Financial Information	Quarterly financial data in millions, except per share data: Three months ended December 31, September 30, June 30, March 31, 2018 2018 2018 2018 Revenue $ 113 $ 118 $ 140 $ 112 Gross profit (loss) $ (14 ) $ 20 $ 44 $ 14 Net loss $ (22 ) $ (32 ) $ (2 ) $ (13 ) Net loss attributable to noncontrolling interests (1) $ (9 ) $ (19 ) $ (34 ) $ (149 ) Net income (loss) attributable to Pattern Energy $ (13 ) $ (13 ) $ 32 $ 136 Earnings (loss) per share Basic $ (0.15 ) $ (0.13 ) $ 0.34 $ 1.39 Diluted $ (0.15 ) $ (0.13 ) $ 0.34 $ 1.32 Cash dividends declared per Class A common share $ 0.4220 $ 0.4220 $ 0.4220 $ 0.4220 (1) As discussed in Note 16. Stockholders' Equity , for the three months ended March 31, 2018, included in net loss attributable to noncontrolling interests is a one-time adjustment of $150 million as a result of the decrease in the federal corporate income tax rate. Three months ended December 31, September 30, June 30, March 31, 2017 2017 2017 2017 Revenue $ 110 $ 92 $ 108 $ 101 Gross profit (loss) $ 16 $ (2 ) $ 21 $ 28 Net income (loss) $ (22 ) $ (48 ) $ (15 ) $ 3 Net loss attributable to noncontrolling interests $ (14 ) $ (18 ) $ (29 ) $ (3 ) Net income (loss) attributable to Pattern Energy $ (8 ) $ (30 ) $ 14 $ 6 Basic and diluted earnings (loss) per share—Class A common stock $ (0.08 ) $ (0.34 ) $ 0.16 $ 0.06 Cash dividends declared per Class A common share $ 0.4220 $ 0.4200 $ 0.4180 $ 0.4138

Organization (Details)

Organization (Details)	Nov. 06, 2018MW	Dec. 31, 2018projectGW	Oct. 31, 2013	Oct. 31, 2012shares
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Number of ownership interests held in renewable energy projects | project		24
Power generation capacity (in GW)	90	4
Shares issued (in shares) | shares				100
Subsidiaries | Pattern Energy Group LP
Consolidation, Less than Wholly Owned Subsidiary, Parent Ownership Interest, Effects of Changes, Net [Line Items]
Ownership percentage			100.00%

Summary of Significant Accoun_4

Summary of Significant Accounting Policies - Additional Information (Details) - USD ($)	3 Months Ended		12 Months Ended
	Dec. 31, 2018	Jun. 30, 2018	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Significant Accounting Policies [Line Items]
Tax expense			$ 32,000,000	$ 12,000,000	$ 9,000,000
Funds deposited by counterparty	$ 6,000,000		6,000,000	30,000,000
Counterparty deposit liability	6,000,000		6,000,000	30,000,000
Impairment expense			7,000,000	0	0
Commitment to provide additional funding to unconsolidated investments	$ 0		$ 0	0	0
Contract terms			As the power purchase agreement is an operating lease, the advanced lease payments will be recorded as lease revenue on a straight-line basis over the 25-year term of the agreement.
Contingent rental revenue			$ 381,000,000	$ 317,000,000	$ 262,000,000
Minimum | Easements land option and mining rights agreements
Significant Accounting Policies [Line Items]
Term of estimated useful lives (in years)			9 years
Maximum | Easements land option and mining rights agreements
Significant Accounting Policies [Line Items]
Term of estimated useful lives (in years)			50 years
Wind farms constructed before 2011
Significant Accounting Policies [Line Items]
Property, plant and equipment useful lives (in years)			20 years
Wind farms constructed after 2011 | Minimum
Significant Accounting Policies [Line Items]
Property, plant and equipment useful lives (in years)			25 years
Wind farms constructed after 2011 | Maximum
Significant Accounting Policies [Line Items]
Property, plant and equipment useful lives (in years)			30 years
Solar Facilities
Significant Accounting Policies [Line Items]
Property, plant and equipment useful lives (in years)			25 years
Transmission asset
Significant Accounting Policies [Line Items]
Property, plant and equipment useful lives (in years)			50 years
Non wind farms assets | Minimum
Significant Accounting Policies [Line Items]
Property, plant and equipment useful lives (in years)			2 years
Non wind farms assets | Maximum
Significant Accounting Policies [Line Items]
Property, plant and equipment useful lives (in years)			5 years
Restatement Adjustment
Significant Accounting Policies [Line Items]
Tax expense		$ 1,000,000
Gulf Wind | Wind Farm Facility, Portion To Be Abandoned
Significant Accounting Policies [Line Items]
Property, plant and equipment useful lives (in years)	15 months

Summary of Significant Accoun_5

Summary of Significant Accounting Policies - Reconciliation of Cash and Cash Equivalents and Restricted Cash As Presented in SCF (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Accounting Policies [Abstract]
Cash and cash equivalents	$ 101	$ 117	$ 84
Restricted cash - current	4	9	12
Restricted cash	18	12	13
Cash, cash equivalents and restricted cash shown in the consolidated statements of cash flows	$ 123	$ 138	$ 109	$ 146

Summary of Significant Accoun_6

Summary of Significant Accounting Policies - Schedule of Significant Customers (Details) - Customer Concentration Risk - Revenue	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Morgan Stanley Capital Group Inc.
Concentration Risk [Line Items]
Concentrations of credit risk (percent)	7.20%	9.10%	10.90%
PG&E
Concentration Risk [Line Items]
Concentrations of credit risk (percent)		5.30%	6.80%	8.50%
PREPA
Concentration Risk [Line Items]
Concentrations of credit risk (percent)	4.10%	4.20%	6.00%
San Diego Gas & Electric
Concentration Risk [Line Items]
Concentrations of credit risk (percent)	12.20%	13.40%	14.60%
Southern California Edison Company
Concentration Risk [Line Items]
Concentrations of credit risk (percent)	11.90%	5.80%	0.00%

Summary of Significant Accoun_7

Summary of Significant Accounting Policies - Geographical Information (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue	$ 113	$ 118	$ 140	$ 112	$ 110	$ 92	$ 108	$ 101	$ 483	$ 411	$ 354
Property, plant and equipment, net	4,119				3,965				4,119	3,965
United States
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue									346	315	285
Property, plant and equipment, net	3,124				3,121				3,124	3,121
Canada
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue									83	62	39
Property, plant and equipment, net	745				550				745	550
Japan
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue									33	0	0
Property, plant and equipment, net	250				0				250	0
Chile
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenue									21	34	$ 30
Property, plant and equipment, net	$ 0				$ 294				$ 0	$ 294

Revenue - Disaggregation of Rev

Revenue - Disaggregation of Revenue (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									$ 103	$ 100	$ 95
Revenue	$ 113	$ 118	$ 140	$ 112	$ 110	$ 92	$ 108	$ 101	483	411	354
Electricity sales under PSA
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									74	65	69
Electricity sales to market
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									14	21	16
REC sales
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									7	7	5
Electricity sales from contracts with customers
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									95	93	90
Related party management service fees
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									8	7	5
Other revenue from contracts with customers
Disaggregation of Revenue [Line Items]
Total revenue from contracts with customers									8	7	5
Other electricity sales
Disaggregation of Revenue [Line Items]
Revenue									369	309	257
Other revenue
Disaggregation of Revenue [Line Items]
Revenue									$ 11	$ 2	$ 2

Revenue - Performance Obligatio

Revenue - Performance Obligations (Details) $ in Millions	12 Months Ended
	Dec. 31, 2018USD ($)
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2019-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligation	$ 79
Remaining performance obligation, period	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligation	$ 66
Remaining performance obligation, period	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligation	$ 67
Remaining performance obligation, period	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2022-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligation	$ 67
Remaining performance obligation, period	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2023-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligation	$ 67
Remaining performance obligation, period	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2024-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligation	$ 622
Remaining performance obligation, period
REC sales | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2019-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligation	$ 20
Remaining performance obligation, percent	61.00%
Remaining performance obligation, period	24 months

Divested Operations - Narrative

Divested Operations - Narrative (Details) - El Arrayan SPA - Discontinued Operations, Disposed of by Sale $ in Millions	Aug. 20, 2018USD ($)	Dec. 31, 2018USD ($)	May 21, 2018kmMW
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Ownership interest			71.00%
Distance of facility from Santiago | km			400
Generating capacity | MW			81
Cash proceeds	$ 70
Impairment loss		$ 7

Acquisitions - Asset Acquisitio

Acquisitions - Asset Acquisitions (Details)	Nov. 20, 2018USD ($)MW	Nov. 06, 2018MW	Aug. 10, 2018USD ($)MW	Aug. 10, 2017USD ($)MW	Dec. 31, 2018USD ($)GW
Schedule of Asset Acquisition [Line Items]
Power generation capacity (in MW)		90			4
Stillwater Acquisition
Schedule of Asset Acquisition [Line Items]
Power generation capacity (in MW) | MW	80
Consideration transferred	$ 111,000,000
Transaction costs capitalized	1,000,000
Gain (loss) recognized upon acquisition	$ 0
MSM
Schedule of Asset Acquisition [Line Items]
Power generation capacity (in MW) | MW			143
Consideration transferred			$ 31,000,000
Gain (loss) recognized upon acquisition			$ 0
Transaction-related expenses incurred					$ 1,000,000
Meikle
Schedule of Asset Acquisition [Line Items]
Percentage of shares acquired				50.99%
Power generation capacity (in MW) | MW				179
Consideration transferred				$ 58,000,000
Transaction costs capitalized				$ 1,000,000
Stillwater Wind LLC | Stillwater New Energy Holdings LLC | Stillwater Acquisition
Schedule of Asset Acquisition [Line Items]
Percentage of shares acquired	100.00%
MSM LP Holdings LP | MSM
Schedule of Asset Acquisition [Line Items]
Percentage of shares acquired			51.00%
MSM | MSM LP Holdings LP | MSM
Schedule of Asset Acquisition [Line Items]
Percentage of shares acquired			99.98%
Pattern MSM GP Holdings, Inc. | MSM
Schedule of Asset Acquisition [Line Items]
Percentage of shares acquired			70.00%
Pattern Development MSM Management ULC | MSM
Schedule of Asset Acquisition [Line Items]
Percentage of shares acquired			70.00%
PSP Investments And Allianz Renewable Energy Partners Of America, LLC | Stillwater Acquisition
Schedule of Asset Acquisition [Line Items]
Consideration transferred	$ 95,000,000

Acquisitions - Business Combina

Acquisitions - Business Combinations (Details) $ in Millions	Nov. 06, 2018MW	Mar. 07, 2018USD ($)MW	Apr. 21, 2017USD ($)KilovoltmiMW	Sep. 30, 2018USD ($)	Dec. 31, 2018USD ($)GW	Dec. 31, 2017USD ($)
Business Acquisition [Line Items]
Power generation capacity (in MW)	90				4
Goodwill					$ 58	$ 0
Class B membership interest in Broadview Holdings
Business Acquisition [Line Items]
Ownership percentage			100.00%
Western Interconnect
Business Acquisition [Line Items]
Ownership percentage			99.00%
Tsugaru Holdings
Business Acquisition [Line Items]
Consideration transferred		$ 264
Contingent consideration		106
Debt assumed		181
Transaction related expenses				$ 1
Goodwill		$ 60
Increase in property, plant and equipment, net				7
Decrease in construction in progress				3
Increase in other assumed liabilities				6
Decrease in deferred tax liabilities				$ 2
Broadview Project
Business Acquisition [Line Items]
Consideration transferred			$ 190
Contingent consideration			21
Goodwill			$ 0
Ownership interest acquired (percent)			100.00%
Aomori Prefecture, Japan | Tsugaru Holdings | Tsugaru
Business Acquisition [Line Items]
Power generation capacity (in MW) | MW		122
Kochi Prefecture, Japan | Tsugaru Holdings | Ohorayama
Business Acquisition [Line Items]
Power generation capacity (in MW) | MW		33
Kochi Prefecture, Japan | Tsugaru Holdings | Otsuki
Business Acquisition [Line Items]
Power generation capacity (in MW) | MW		12
Shimane Prefecture, Japan | Tsugaru Holdings | Kanagi
Business Acquisition [Line Items]
Power generation capacity (in MW) | MW		10
Chiba Prefecture, Japan | Tsugaru Holdings | Futtsu
Business Acquisition [Line Items]
Power generation capacity (in MW) | MW		29
Term Conversion Of Tsugaru Construction Loan | Tsugaru Holdings
Business Acquisition [Line Items]
Contingent consideration		$ 103
Term Conversion Of Ohorayama Construction Loan | Tsugaru Holdings
Business Acquisition [Line Items]
Contingent consideration		$ 3
Broadview
Business Acquisition [Line Items]
Power generation capacity (in MW) | MW			324
Western Interconnect
Business Acquisition [Line Items]
Transmission line length | mi			35
Transmission-level voltage (in kV) | Kilovolt			345

Acquisitions - Schedule of Asse

Acquisitions - Schedule of Assets Acquired and Liabilities Assumed (Details) - USD ($) $ in Millions	Nov. 20, 2018	Aug. 10, 2018	Mar. 07, 2018	Aug. 10, 2017	Apr. 21, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Allocation
Goodwill						$ 60
Business Acquisition [Line Items]
Cash paid for acquisitions, net of cash and restricted cash acquired						415	$ 297	$ 136
Goodwill						$ 58	$ 0
Tsugaru Holdings
Business Acquisition [Line Items]
Cash paid for acquisitions, net of cash and restricted cash acquired			$ 158
Contingent consideration			106
Consideration transferred			264
Property, plant and equipment, net			269
Construction in progress			179
Intangible assets			103
Goodwill			60
Other assets acquired			20
Debt			(181)
Deferred tax liabilities			(65)
Advanced lease revenue			0
Other liabilities assumed			(110)
Total consideration before non-controlling interest			275
Less: noncontrolling interests			(11)
Total consideration			$ 264
Broadview Project
Business Acquisition [Line Items]
Cash paid for acquisitions, net of cash and restricted cash acquired					$ 169
Contingent consideration					21
Consideration transferred					190
Property, plant and equipment, net					628
Construction in progress					0
Intangible assets					22
Goodwill					0
Other assets acquired					12
Debt					(51)
Deferred tax liabilities					0
Advanced lease revenue					0
Other liabilities assumed					(95)
Total consideration before non-controlling interest					516
Less: noncontrolling interests					(326)
Total consideration					$ 190
MSM
Asset Acquisition, Purchase Price [Abstract]
Cash paid for acquisitions, net of cash and restricted cash acquired		$ 31
Contingent consideration		0
Consideration transferred		31
Allocation
Property, plant and equipment, net		270
Construction in progress		0
Intangibles		0
Goodwill		0
Other assets acquired		38
Debt		(196)
Deferred tax liabilities		0
Advanced lease revenue		(29)
Other liabilities assumed		(14)
Assets and liabilities assumed before noncontrolling interests		69
Less: noncontrolling interests		(38)
Total consideration allocated to acquired assets and liabilities		$ 31
Stillwater Acquisition
Asset Acquisition, Purchase Price [Abstract]
Cash paid for acquisitions, net of cash and restricted cash acquired	$ 111
Contingent consideration	0
Consideration transferred	111
Allocation
Property, plant and equipment, net	120
Construction in progress	0
Intangibles	0
Goodwill	0
Other assets acquired	4
Debt	0
Deferred tax liabilities	0
Advanced lease revenue	0
Other liabilities assumed	(13)
Assets and liabilities assumed before noncontrolling interests	111
Less: noncontrolling interests	0
Total consideration allocated to acquired assets and liabilities	$ 111
Meikle
Asset Acquisition, Purchase Price [Abstract]
Cash paid for acquisitions, net of cash and restricted cash acquired				$ 58
Contingent consideration				0
Consideration transferred				58
Allocation
Property, plant and equipment, net				376
Construction in progress				0
Intangibles				29
Goodwill				0
Other assets acquired				8
Debt				(266)
Deferred tax liabilities				0
Advanced lease revenue				0
Other liabilities assumed				(24)
Assets and liabilities assumed before noncontrolling interests				123
Less: noncontrolling interests				(65)
Total consideration allocated to acquired assets and liabilities				$ 58

Acquisitions - Schedule of Supp

Acquisitions - Schedule of Supplemental Pro Forma Data (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Business Combinations [Abstract]
Pro forma total revenue	$ 487	$ 435
Pro forma total expenses	556	520
Pro forma net loss	(69)	(85)
Less: pro forma net loss attributable to noncontrolling interest	(211)	(65)
Pro forma net income (loss) attributable to Pattern Energy	$ 142	$ (20)

Acquisitions - Schedule of Amou

Acquisitions - Schedule of Amounts Included in Consolidated Statements of Operations (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Business Combinations [Abstract]
Total revenue	$ 96	$ 33
Total expenses	105	50
Net loss	(9)	(17)
Less: net loss attributable to noncontrolling interest	(48)	(17)
Net income attributable to Pattern Energy	$ 39	$ 0

Intangible Assets and Liabili_3

Intangible Assets and Liabilities and Goodwill - Schedule of Major Components of the Finite-Lived Intangible Assets and Liability (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Finite-Lived Intangible Assets [Line Items]
Finite lived intangible assets, Gross	$ 252	$ 155
Finite lived intangible assets, Accumulated Amortization	(33)	(19)
Finite lived intangible assets, Net	219	136
Finite lived intangible liability, Gross	69
Finite lived intangible liability, Accumulated Amortization	(13)
Finite lived intangible liability, Net	$ 56	$ 51
Power purchase agreement
Finite-Lived Intangible Assets [Line Items]
Weighted average remaining life - intangible assets	15 years	15 years
Weighted average remaining life - intangible liability	14 years	15 years
Finite lived intangible assets, Gross	$ 225	$ 127
Finite lived intangible assets, Accumulated Amortization	(31)	(18)
Finite lived intangible assets, Net	194	109
Finite lived intangible liability, Gross	60	60
Finite lived intangible liability, Accumulated Amortization	(13)	(9)
Finite lived intangible liability, Net	$ 47	$ 51
Industrial revenue bond tax savings
Finite-Lived Intangible Assets [Line Items]
Weighted average remaining life - intangible assets	23 years	24 years
Finite lived intangible assets, Gross	$ 13	$ 13
Finite lived intangible assets, Accumulated Amortization	(1)	0
Finite lived intangible assets, Net	$ 12	$ 13
Other intangible assets
Finite-Lived Intangible Assets [Line Items]
Weighted average remaining life - intangible assets	33 years	34 years
Finite lived intangible assets, Gross	$ 14	$ 15
Finite lived intangible assets, Accumulated Amortization	(1)	(1)
Finite lived intangible assets, Net	$ 13	$ 14
Leasehold interest
Finite-Lived Intangible Assets [Line Items]
Weighted average remaining life - intangible liability	22 years
Finite lived intangible liability, Gross	$ 9
Finite lived intangible liability, Accumulated Amortization	0
Finite lived intangible liability, Net	$ 9

Property, Plant and Equipment -

Property, Plant and Equipment - Schedule of Property, Plant and Equipment (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 5,082	$ 4,747
Less: accumulated depreciation	(963)	(782)
Property, plant and equipment, net	4,119	3,965
Operating wind farms
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	4,972	4,641
Transmission line
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	94	94
Furniture, fixtures and equipment
Property, Plant and Equipment [Line Items]
Property, plant and equipment, gross	$ 16	$ 12

Intangible Assets and Liabili_4

Intangible Assets and Liabilities and Goodwill - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Mar. 07, 2018
Finite-Lived Intangible Assets [Line Items]
Goodwill	$ 58	$ 0
Power purchase agreement
Finite-Lived Intangible Assets [Line Items]
Intangible assets, amortization expense (less than $1 million)	9	4	$ 3
Other intangible assets
Finite-Lived Intangible Assets [Line Items]
Intangible assets, amortization expense (less than $1 million)	$ 1	$ 1	$ 1
Tsugaru Holdings
Finite-Lived Intangible Assets [Line Items]
Goodwill				$ 60
Intangible assets				103
Intangible liabilities				$ 9

Property, Plant and Equipment_2

Property, Plant and Equipment - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Property, Plant and Equipment [Abstract]
Depreciation expense related to property, plant and equipment	$ 245	$ 195	$ 172

Intangible Assets and Liabili_5

Intangible Assets and Liabilities and Goodwill - Schedule of Estimated Future Amortization Expense (Details) $ in Millions	Dec. 31, 2018USD ($)
Finite-Lived Intangible Liabilities, Amortization Expense, Maturity Schedule [Abstract]
2,019	$ 0
2,020	0
2,021	0
2,022	0
2,023	0
Thereafter	(7)
Power purchase agreement
Finite-Lived Intangible Assets, Amortization Expense, Maturity Schedule [Abstract]
2,019	10
2,020	10
2,021	10
2,022	10
2,023	10
Thereafter	101
Industrial revenue bond tax savings
Finite-Lived Intangible Assets, Amortization Expense, Maturity Schedule [Abstract]
2,019	1
2,020	1
2,021	1
2,022	1
2,023	1
Thereafter	9
Other intangible assets
Finite-Lived Intangible Assets, Amortization Expense, Maturity Schedule [Abstract]
2,019	1
2,020	1
2,021	1
2,022	1
2,023	1
Thereafter	$ 10

Intangible Assets and Liabili_6

Intangible Assets and Liabilities and Goodwill - Goodwill (Details) $ in Millions	12 Months Ended
	Dec. 31, 2018USD ($)
Goodwill [Roll Forward]
Goodwill, beginning balance	$ 0
Goodwill	60
Foreign currency translation adjustment	(2)
Goodwill, ending balance	$ 58

Variable Interest Entities (Det

Variable Interest Entities (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Variable Interest Entity [Line Items]
Unconsolidated investments	$ 270	$ 311
Cash and cash equivalents	101	117	$ 84
Trade receivables	50	55
Prepaid expenses	18	18
Other current assets	16	21
Total current assets	211	270
Construction in progress	259	0
Property, plant and equipment, net	4,119	3,965
Deferred financing costs	8	8
Intangible assets, net	219	136
Other assets	34	24
Total assets	5,294	4,742
Accounts payable and other accrued liabilities	67	54
Accrued construction costs	27	1
Current portion of long-term debt, net	56	52
Other current liabilities	11	12
Total current liabilities	478	218
Long-term debt, net	2,004	1,879
Intangible liabilities, net	56	51
Asset retirement obligations	185	57
Other long-term liabilities	71	50
Deferred revenue	26	0
Total liabilities	3,135	2,394
Variable Interest Entity, Primary Beneficiary
Variable Interest Entity [Line Items]
Cash and cash equivalents	36	33
Restricted cash - current	4	4
Trade receivables	13	13
Prepaid expenses	6	5
Other current assets	2	3
Total current assets	61	58
Restricted cash	3	3
Construction in progress	1	0
Property, plant and equipment, net	2,156	1,985
Deferred financing costs	2	2
Intangible assets, net	12	12
Other assets	12	13
Total assets	2,247	2,073
Accounts payable and other accrued liabilities	27	27
Accrued construction costs	1	1
Current portion of long-term debt, net	4	0
Other current liabilities	5	5
Total current liabilities	37	33
Long-term debt, net	149	0
Intangible liabilities, net	48	51
Asset retirement obligations	57	22
Other long-term liabilities	36	25
Deferred revenue	26	0
Total liabilities	353	131
Pattern Development
Variable Interest Entity [Line Items]
Unconsolidated investments	$ 144	$ 62

Unconsolidated Investments - Sc

Unconsolidated Investments - Schedule of Projects Accounted under Equity Method of Accounting (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Schedule of Equity Method Investments [Line Items]
Unconsolidated investments	$ 270	$ 311
South Kent
Schedule of Equity Method Investments [Line Items]
Unconsolidated investments	$ 5	$ 6
Ownership interest (percent)	50.00%	50.00%
Grand
Schedule of Equity Method Investments [Line Items]
Unconsolidated investments	$ 5	$ 7
Ownership interest (percent)	45.00%	45.00%
K2
Schedule of Equity Method Investments [Line Items]
Unconsolidated investments	$ 0	$ 103
Ownership interest (percent)	0.00%	33.30%
Armow
Schedule of Equity Method Investments [Line Items]
Unconsolidated investments	$ 116	$ 133
Ownership interest (percent)	50.00%	50.00%
Pattern Development
Schedule of Equity Method Investments [Line Items]
Unconsolidated investments	$ 144	$ 62
Ownership interest (percent)	29.30%	20.90%

Unconsolidated Investments - Ad

Unconsolidated Investments - Additional Information (Details)	Nov. 06, 2018USD ($)MW	Jul. 27, 2017USD ($)	Dec. 31, 2018USD ($)GW	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)
Schedule of Equity Method Investments [Line Items]
Power generation capacity (in MW)	90		4
Capitalized transaction costs				$ 2,000,000
Amortization of basis difference for equity method investment			$ 11,000,000	$ 11,000,000	$ 6,000,000
K2
Schedule of Equity Method Investments [Line Items]
Proceeds from sale	$ 158,000,000
Gain on sale	$ 71,000,000
Ownership interest (percent)			0.00%	33.30%
South Kent
Schedule of Equity Method Investments [Line Items]
PPA of project (in years)			20 years
Ownership interest (percent)			50.00%	50.00%
Grand
Schedule of Equity Method Investments [Line Items]
PPA of project (in years)			20 years
Ownership interest (percent)			45.00%	45.00%
Armow
Schedule of Equity Method Investments [Line Items]
Ownership interest (percent)			50.00%	50.00%
Pattern Development 2.0
Schedule of Equity Method Investments [Line Items]
Right to contribute, maximum amount			$ 300,000,000
Ownership interest (percent)			29.00%
Initial capital call		$ 60,000,000
Aggregate cost			$ 183,000,000
Excess of investment balance over equity in net assets		$ 41,000,000

Debt - Schedule of Long Term De

Debt - Schedule of Long Term Debt (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Long-term debt, gross	$ 2,315	$ 1,968
Unamortized premium/discount, net	(11)	(14)
Unamortized financing costs	(21)	(23)
Long term debt, net	2,283	1,931
Revolving credit facility, current	198	0
Revolving credit facility	25	0
Current portion of long-term debt, net of financing costs	56	52
Long term debt, net of financing costs	2,004	1,879
Corporate Revolving Credit Facility
Debt Instrument [Line Items]
Long-term debt, gross	$ 198	0
Effective Interest Rate (percent)	4.01%
Long term debt, Maturity	November 2,022
2020 Notes
Debt Instrument [Line Items]
Long-term debt, gross	$ 225	225
Contractual interest rate (percent)	4.00%
Effective Interest Rate (percent)	6.60%
Long term debt, Maturity	July 2,020
2024 Notes
Debt Instrument [Line Items]
Long-term debt, gross	$ 350	350
Contractual interest rate (percent)	5.88%
Effective Interest Rate (percent)	5.88%
Long term debt, Maturity	February 2,024
El Arrayan EKF team loan
Debt Instrument [Line Items]
Long-term debt, gross	$ 0	99
Contractual interest rate (percent)	0.00%
Effective Interest Rate (percent)	0.00%
Long term debt, Maturity	N/A
Santa Isabel term loan
Debt Instrument [Line Items]
Long-term debt, gross	$ 100	104
Contractual interest rate (percent)	4.57%
Effective Interest Rate (percent)	4.57%
Long term debt, Maturity	September 2,033
Mont Sainte Marguerite-Med Term Loan
Debt Instrument [Line Items]
Long-term debt, gross	$ 62	0
Contractual interest rate (percent)	3.97%
Effective Interest Rate (percent)	3.97%
Long term debt, Maturity	December 2,029
Mont Sainte Marguerite-Long Term loan
Debt Instrument [Line Items]
Long-term debt, gross	$ 93	0
Contractual interest rate (percent)	5.04%
Effective Interest Rate (percent)	5.04%
Long term debt, Maturity	June 2,042
Japan Credit Facility
Debt Instrument [Line Items]
Long-term debt, gross	$ 25	0
Effective Interest Rate (percent)	1.82%
Long term debt, Maturity	August 2,022
Ocotillo commercial term loan
Debt Instrument [Line Items]
Long-term debt, gross	$ 281	289
Contractual interest rate (percent)	4.30%
Effective Interest Rate (percent)	4.01%
Long term debt, Maturity	June 2,033
El Arrayan commercial term loan
Debt Instrument [Line Items]
Long-term debt, gross	$ 0	90
Contractual interest rate (percent)	0.00%
Effective Interest Rate (percent)	0.00%
Long term debt, Maturity	N/A
Spring Valley term loan
Debt Instrument [Line Items]
Long-term debt, gross	$ 0	126
Contractual interest rate (percent)	0.00%
Effective Interest Rate (percent)	0.00%
Long term debt, Maturity	N/A
St Joseph term loan
Debt Instrument [Line Items]
Long-term debt, gross	$ 152	172
Contractual interest rate (percent)	4.06%
Effective Interest Rate (percent)	4.11%
Long term debt, Maturity	November 2,033
Western Interconnect term loan
Debt Instrument [Line Items]
Long-term debt, gross	$ 52	54
Contractual interest rate (percent)	4.19%
Effective Interest Rate (percent)	4.21%
Long term debt, Maturity	May 2,034
Meikle term loan
Debt Instrument [Line Items]
Long-term debt, gross	$ 239	267
Contractual interest rate (percent)	3.81%
Effective Interest Rate (percent)	3.97%
Long term debt, Maturity	May 2,024
Futtsu term loan
Debt Instrument [Line Items]
Long-term debt, gross	$ 75	0
Contractual interest rate (percent)	1.07%
Effective Interest Rate (percent)	1.85%
Long term debt, Maturity	December 2,033
Ohorayama term loan
Debt Instrument [Line Items]
Long-term debt, gross	$ 93	0
Contractual interest rate (percent)	0.87%
Effective Interest Rate (percent)	0.88%
Long term debt, Maturity	February 2,036
Tsugaru Construction Loan
Debt Instrument [Line Items]
Long-term debt, gross	$ 131	0
Contractual interest rate (percent)	0.72%
Effective Interest Rate (percent)	0.72%
Long term debt, Maturity	March 2,038
Tsugaru Holdings Loan Agreement
Debt Instrument [Line Items]
Long-term debt, gross	$ 59	0
Contractual interest rate (percent)	3.07%
Effective Interest Rate (percent)	3.07%
Long term debt, Maturity	July 2,022
Hatchet Ridge financing lease obligation
Debt Instrument [Line Items]
Long-term debt, gross	$ 180	$ 192
Contractual interest rate (percent)	1.43%
Effective Interest Rate (percent)	1.43%
Long term debt, Maturity	December 2,032

Debt - Summary of Principal Pay

Debt - Summary of Principal Payments Due under Long Term Debt (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Debt Disclosure [Abstract]
2,019	$ 254
2,020	288
2,021	74
2,022	154
2,023	73
Thereafter	1,472
Total	$ 2,315	$ 1,968

Debt - Schedule of Reconciliati

Debt - Schedule of Reconciliation of Interest Expense (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Debt Disclosure [Abstract]
Corporate-level interest and commitment fees incurred	$ 38	$ 34	$ 18
Project-level interest and commitment fees incurred	64	55	48
Capitalized interest, commitment fees, and letter of credit fees	(4)	0	0
Amortization of debt discount/premium, net	5	5	4
Amortization of financing costs	6	8	7
Other interest	0	0	1
Interest expense	$ 109	$ 102	$ 78

Debt - Corporate Level Debt (De

Debt - Corporate Level Debt (Details)	Nov. 21, 2017USD ($)	Jul. 31, 2015$ / shares	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)	Nov. 20, 2017USD ($)
Convertible Debt
Debt Instrument [Line Items]
Conversion ratio (shares per $1000 of debt)			35.8997
Revolving Credit Facility
Debt Instrument [Line Items]
Credit agreement	$ 440,000,000				$ 500,000,000
Term (in years)	5 years
Remaining borrowing capacity			$ 197,000,000
Letters-of-credit outstanding			$ 45,000,000	$ 48,000,000
Revolving Credit Facility | Minimum
Debt Instrument [Line Items]
Commitment fee (percent)			0.30%
Revolving Credit Facility | Maximum
Debt Instrument [Line Items]
Commitment fee (percent)			0.50%
Revolving Credit Facility | Federal Funds Rate
Debt Instrument [Line Items]
Basis spread on interest rate (percent)			0.50%
Revolving Credit Facility | Eurodollar
Debt Instrument [Line Items]
Basis spread on variable rate interest period			1.00%
Revolving Credit Facility | Eurodollar | Minimum
Debt Instrument [Line Items]
Basis spread on interest rate (percent)			1.625%
Revolving Credit Facility | Eurodollar | Maximum
Debt Instrument [Line Items]
Basis spread on interest rate (percent)			1.875%
Revolving Credit Facility | Base Rate | Minimum
Debt Instrument [Line Items]
Basis spread on interest rate (percent)			0.625%
Revolving Credit Facility | Base Rate | Maximum
Debt Instrument [Line Items]
Basis spread on interest rate (percent)			0.875%
Revolving Credit Facility | CDOR
Debt Instrument [Line Items]
Basis spread on interest rate (percent)			0.50%
Revolving Credit Facility | CDOR | Minimum
Debt Instrument [Line Items]
Basis spread on interest rate (percent)			0.625%
Interest accrual rate (percent)			1.625%
Revolving Credit Facility | CDOR | Maximum
Debt Instrument [Line Items]
Basis spread on interest rate (percent)			0.875%
Interest accrual rate (percent)			1.875%
Parent Company | Convertible Debt
Debt Instrument [Line Items]
Face amount			$ 225,000,000	$ 225,000,000
Contractual interest rate (percent)		4.00%
Conversion ratio (shares per $1000 of debt)		35.4925		35.8997
Conversion price (in dollars per share) | $ / shares		$ 28.175
Dividend threshold trigger (in dollars per share) | $ / shares		$ 0.363

Debt - Convertible Senior Note

Debt - Convertible Senior Note (Details)	Jul. 31, 2015$ / shares	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)
Debt Instrument [Line Items]
Amortization of debt discount		$ 5,000,000	$ 5,000,000	$ 4,000,000
Convertible Debt
Debt Instrument [Line Items]
Conversion ratio (shares per $1000 of debt)		35.8997
Parent Company | Convertible Debt
Debt Instrument [Line Items]
Principal		$ 225,000,000	225,000,000
Unamortized debt discount		(8,000,000)	(13,000,000)
Unamortized financing costs		(2,000,000)	(3,000,000)
Carrying value of convertible senior notes		215,000,000	209,000,000
Carrying value of the equity component		24,000,000	$ 24,000,000
Equity issuance costs		$ 1,000,000
Interest rate (percent)	4.00%
Conversion ratio (shares per $1000 of debt)	35.4925		35.8997
Conversion price (in dollars per share) | $ / shares	$ 28.175
Dividend threshold trigger (in dollars per share) | $ / shares	$ 0.363

Debt - Project Debt (Details)

Debt - Project Debt (Details) - USD ($)	1 Months Ended				3 Months Ended	12 Months Ended
	Dec. 31, 2018	Aug. 31, 2018	Mar. 31, 2018	Dec. 31, 2010	Jun. 30, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Debt Instrument [Line Items]
Long-term debt, gross	$ 2,315,000,000					$ 2,315,000,000	$ 1,968,000,000
Loss on extinguishment of debt						(6,000,000)	(9,000,000)	$ 0
Western Interconnect
Debt Instrument [Line Items]
Long-term debt, gross	52,000,000					52,000,000	54,000,000
Letters-of-credit outstanding	$ 4,000,000					$ 4,000,000
Contractual interest rate (percent)	4.19%					4.19%
Western Interconnect, Refinanced
Debt Instrument [Line Items]
Long-term debt, gross	$ 90,000,000					$ 90,000,000
Letters-of-credit outstanding	5,000,000					5,000,000
Loss on extinguishment of debt						(2,000,000)
Amount paid to existing lenders						1,000,000
Spring Valley term loan
Debt Instrument [Line Items]
Long-term debt, gross	0					$ 0	126,000,000
Loss on extinguishment of debt	$ (4,000,000)
Extinguishment of debt, percent	100.00%
Extinguishment of debt, amount	$ 119,000,000
Contractual interest rate (percent)	0.00%					0.00%
Tsugaru Construction Loan
Debt Instrument [Line Items]
Long-term debt, gross	$ 131,000,000					$ 131,000,000	0
Contractual interest rate (percent)	0.72%					0.72%
Tsugaru Construction Loan | Tokyo Interbank Offered Rate (TIBOR)
Debt Instrument [Line Items]
Basis spread on interest rate (percent)			0.65%
Japanese Consumption Tax Facility
Debt Instrument [Line Items]
Commitment fee (percent)			0.30%
Tsugaru Holdings Loan Agreement
Debt Instrument [Line Items]
Long-term debt, gross	$ 59,000,000					$ 59,000,000	0
Credit agreement	$ 70,100,000					$ 70,100,000
Commitment fee (percent)			0.50%
Contractual interest rate (percent)	3.07%					3.07%
Tsugaru Holdings Loan Agreement | Tokyo Interbank Offered Rate (TIBOR)
Debt Instrument [Line Items]
Basis spread on interest rate (percent)			3.00%
Hatchet Ridge Term Loan
Debt Instrument [Line Items]
Long-term debt, gross	$ 180,000,000					$ 180,000,000	192,000,000
Contractual interest rate (percent)	1.43%					1.43%
Term (in years)				22 years
Payments of financing lease obligations						$ 15,000,000	$ 13,000,000	$ 15,000,000
Scenario, Forecast | Western Interconnect, Refinanced
Debt Instrument [Line Items]
Amount of incremental borrowing from refinancing					$ 38,000,000
Japan Credit Facility
Debt Instrument [Line Items]
Credit agreement		$ 31,900,000
Commitment fee (percent)		0.30%
Remaining borrowing capacity	$ 7,000,000					$ 7,000,000
Japan Credit Facility | Tokyo Interbank Offered Rate (TIBOR) | Minimum
Debt Instrument [Line Items]
Basis spread on interest rate (percent)		1.75%
Japan Credit Facility | Tokyo Interbank Offered Rate (TIBOR) | Maximum
Debt Instrument [Line Items]
Basis spread on interest rate (percent)		2.25%
Tsugaru Credit Facility | Tsugaru Construction Loan
Debt Instrument [Line Items]
Credit agreement			$ 371,000,000
Term, following conversion			18 years
Tsugaru Credit Facility | Debt Service Reserve Account LC
Debt Instrument [Line Items]
Face amount			$ 20,000,000
Tsugaru Credit Facility | O&M Reserve Account LC
Debt Instrument [Line Items]
Face amount			$ 8,000,000
Tsugaru Credit Facility | Tsugaru Letter Of Credit Facilities
Debt Instrument [Line Items]
Contractual interest rate (percent)			1.10%
Unused capacity, commitment fee percentage			0.30%
Tsugaru Credit Facility | Japanese Consumption Tax Facility
Debt Instrument [Line Items]
Credit agreement			$ 33,800,000
Tsugaru Credit Facility | Japanese Consumption Tax Facility | Tokyo Interbank Offered Rate (TIBOR)
Debt Instrument [Line Items]
Basis spread on interest rate (percent)			0.30%

Asset Retirement Obligation - R

Asset Retirement Obligation - Reconciliation of Aggregate Carrying Amounts (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Asset Retirement Obligation, Roll Forward Analysis [Roll Forward]
Beginning asset retirement obligations	$ 57	$ 45
Net additions during the year	67	9
Foreign currency translation adjustment	(2)	0
Divested operations	3	0
Revision in estimated cash flows	85	0
Accretion expense	5	3
Ending asset retirement obligations	$ 209	$ 57

Derivative Instruments - Schedu

Derivative Instruments - Schedule of Derivative Instruments Classified as Assets (Liabilities) (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Derivative [Line Items]
Derivative assets, current	$ 14	$ 19
Derivative assets, long-term	9	10
Derivative liabilities, current	2	8
Derivative liabilities, long-term	31	21
Designated as Hedging Instrument | Interest rate swaps
Derivative [Line Items]
Derivative assets, current	0	0
Derivative assets, long-term	3	2
Derivative liabilities, current	2	4
Derivative liabilities, long-term	25	18
Undesignated Derivative Instruments | Interest rate swaps
Derivative [Line Items]
Derivative assets, current	0	0
Derivative assets, long-term	0	0
Derivative liabilities, current	0	1
Derivative liabilities, long-term	4	3
Undesignated Derivative Instruments | Energy derivative
Derivative [Line Items]
Derivative assets, current	7	19
Derivative assets, long-term	0	8
Derivative liabilities, current	0	0
Derivative liabilities, long-term	0	0
Undesignated Derivative Instruments | Foreign currency forward contracts
Derivative [Line Items]
Derivative assets, current	6	0
Derivative assets, long-term	6	0
Derivative liabilities, current	0	3
Derivative liabilities, long-term	2	$ 0
Undesignated Derivative Instruments | Congestion revenue rights
Derivative [Line Items]
Derivative assets, current	1
Derivative assets, long-term	0
Derivative liabilities, current	0
Derivative liabilities, long-term	$ 0

Derivative Instruments - Notion

Derivative Instruments - Notional Amount of Outstanding Derivatives (Details) ¥ in Millions, $ in Millions, $ in Millions	Dec. 31, 2018USD ($)MW	Dec. 31, 2018CAD ($)MW	Dec. 31, 2018JPY (¥)MW	Dec. 31, 2017USD ($)MW	Dec. 31, 2017CAD ($)MW	Dec. 31, 2017JPY (¥)MW
Designated as Hedging Instrument | Interest rate swaps
Derivative [Line Items]
Derivative, notional amount	$ 319	$ 721	¥ 55,675	$ 253	$ 736	¥ 0
Undesignated Derivative Instruments | Interest rate swaps
Derivative [Line Items]
Derivative, notional amount | $	$ 138			$ 85
Undesignated Derivative Instruments | Energy derivative
Derivative [Line Items]
Energy derivative, notional amount	193,252	193,252	193,252	697,471	697,471	697,471
Undesignated Derivative Instruments | Foreign currency forward contracts
Derivative [Line Items]
Derivative, notional amount		$ 106	¥ 11,589		$ 128	¥ 0
Undesignated Derivative Instruments | Congestion revenue rights
Derivative [Line Items]
Energy derivative, notional amount	505	505	505	0	0	0

Derivative Instruments - Summar

Derivative Instruments - Summary of Effects of Cash Flow Hedges on Consolidated Statements of Operations (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) recognized in OCI, effective portion	$ (6)	$ (2)	$ (8)
Interest expense
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) reclassified from accumulated OCI into Income, effective portion	(5)	(10)	(8)
Loss on derivatives
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) reclassified from accumulated OCI into Income, effective portion	$ 0	$ (2)	$ 0

Derivative Instruments - Summ_2

Derivative Instruments - Summary of Effects of Undesignated Derivatives on Consolidated Statement of Operations (Details) - Not Designated as Hedging Instrument - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Interest rate derivatives
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on interest rate derivatives	$ 0	$ (1)	$ (2)
Energy derivative
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on energy derivatives	(3)	5	(1)
Foreign currency forward contracts
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on foreign currency forward contracts	16	(7)	(1)
Foreign currency option contract
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on foreign currency forward contracts	$ 1	$ 0	$ 0

Derivative Instruments - Additi

Derivative Instruments - Additional Information (Details) $ in Millions	12 Months Ended
	Dec. 31, 2018USD ($)	Dec. 31, 2010MWh	Dec. 31, 2017USD ($)
Derivative [Line Items]
Energy derivative, notional amount (in MWh)	$ (1)
Counterparty collateral	6		$ 30
Counterparty collateral liability	$ 6		$ 30
Interest rate swaps | Minimum | Designated as Hedging Instrument
Derivative [Line Items]
Derivative, remaining maturity	60 months
Interest rate swaps | Maximum | Designated as Hedging Instrument
Derivative [Line Items]
Derivative, remaining maturity	292 months
Interest rate swaps | Maximum | Undesignated Derivative Instruments
Derivative [Line Items]
Derivative, remaining maturity	138 months
Foreign currency forward contracts | Minimum
Derivative [Line Items]
Derivative, remaining maturity	3 months
Foreign currency forward contracts | Maximum
Derivative [Line Items]
Derivative, remaining maturity	11 years
Energy derivative | Undesignated Derivative Instruments
Derivative [Line Items]
Energy derivative, notional amount | MWh		504,220

Accumulated Other Comprehensi_3

Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	$ 2,348	$ 1,879	$ 1,776
Amounts reclassified from accumulated other comprehensive loss due to termination/de-designation of interest rate derivatives	5	11	7
Net current period other comprehensive income (loss)	(34)	37	11
Ending balance	2,159	2,348	1,879
Foreign Currency
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	(28)	(43)	(48)
Other comprehensive income (loss) before reclassifications	(37)	15	5
Amounts reclassified from accumulated other comprehensive loss	0	0	0
Net current period other comprehensive income (loss)	(37)	15	5
Ending balance	(65)	(28)	(43)
Effective Portion of Change in Fair Value of Derivatives
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	(5)	(13)	(14)
Other comprehensive income (loss) before reclassifications	(4)	(3)	(7)
Amounts reclassified from accumulated other comprehensive loss	(5)	(11)	(8)
Net current period other comprehensive income (loss)	1	8	1
Ending balance	(4)	(5)	(13)
Proportionate Share of Equity Investee's OCI
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	7	(7)	(12)
Other comprehensive income (loss) before reclassifications	(3)	6	1
Amounts reclassified from accumulated other comprehensive loss	(5)	(8)	(4)
Net current period other comprehensive income (loss)	2	14	5
Ending balance	9	7	(7)
Total
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	(26)	(63)	(74)
Other comprehensive income (loss) before reclassifications	(44)	18	(1)
Amounts reclassified from accumulated other comprehensive loss	(10)	(19)	(12)
Net current period other comprehensive income (loss)	(34)	37	11
Ending balance	$ (60)	$ (26)	$ (63)

Fair Value Measurements - Finan

Fair Value Measurements - Financial Assets and Liabilities Required Fair Value Measurement on Recurring Basis (Details) - Recurring Measurement Basis - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Assets
Assets	$ 23	$ 29
Liabilities
Contingent consideration	130	22
Liabilities	163	51
Interest rate swaps
Assets
Derivative assets	3	2
Liabilities
Derivative liabilities	31	26
Energy derivative
Assets
Derivative assets	7	27
Foreign currency forward contracts
Assets
Derivative assets	12	0
Liabilities
Derivative liabilities	2	3
Congestion revenue rights
Assets
Derivative assets	1
Level 1
Assets
Assets	0	0
Liabilities
Contingent consideration	0	0
Liabilities	0	0
Level 1 | Interest rate swaps
Assets
Derivative assets	0	0
Liabilities
Derivative liabilities	0	0
Level 1 | Energy derivative
Assets
Derivative assets	0	0
Level 1 | Foreign currency forward contracts
Assets
Derivative assets	0	0
Liabilities
Derivative liabilities	0	0
Level 1 | Congestion revenue rights
Assets
Derivative assets	0
Level 2
Assets
Assets	15	2
Liabilities
Contingent consideration	0	0
Liabilities	33	29
Level 2 | Interest rate swaps
Assets
Derivative assets	3	2
Liabilities
Derivative liabilities	31	26
Level 2 | Energy derivative
Assets
Derivative assets	0	0
Level 2 | Foreign currency forward contracts
Assets
Derivative assets	12	0
Liabilities
Derivative liabilities	2	3
Level 2 | Congestion revenue rights
Assets
Derivative assets	0
Level 3
Assets
Assets	8	27
Liabilities
Contingent consideration	130	22
Liabilities	130	22
Level 3 | Interest rate swaps
Assets
Derivative assets	0	0
Liabilities
Derivative liabilities	0	0
Level 3 | Energy derivative
Assets
Derivative assets	7	27
Level 3 | Foreign currency forward contracts
Assets
Derivative assets	0	0
Liabilities
Derivative liabilities	0	$ 0
Level 3 | Congestion revenue rights
Assets
Derivative assets	$ 1

Fair Value Measurements - Recon

Fair Value Measurements - Reconciliation of Derivative Assets Measured at Fair Value (Details) - Energy derivative - Recurring Measurement Basis - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of year	$ 27	$ 41
Total gain (loss) included in electricity sales	(3)	5
Settlements	(17)	(19)
Balance, end of year	$ 7	$ 27

Fair Value Measurements - Addit

Fair Value Measurements - Additional Information (Details) - USD ($) $ in Millions	1 Months Ended	12 Months Ended
	Jul. 31, 2018	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Mar. 07, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent consideration, additional payment					$ 118
Recurring Measurement Basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent consideration		$ 130	$ 22
Recurring Measurement Basis | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent consideration		130	22
Energy derivative | Recurring Measurement Basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Unrealized gain losses		(20)	(14)	$ (23)
Congestion revenue rights | Recurring Measurement Basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Unrealized gain losses		1
Purchases		1
Tsugaru Holdings
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent consideration					106
Term Conversion Of Tsugaru Construction Loan | Tsugaru Holdings
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent consideration arrangements, additional payment, increase per criteria					10
Contingent consideration arrangements, additional payment, decrease per criteria					10
Contingent consideration					103
Term Conversion Of Ohorayama Construction Loan
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Payment for contingent consideration liability	$ 3
Term Conversion Of Ohorayama Construction Loan | Tsugaru Holdings
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent consideration					$ 3
Contingent consideration | Recurring Measurement Basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Purchases		106	21
Total loss included in other income (expense), net		5	1
Other Income (Expense) | Contingent consideration | Recurring Measurement Basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total loss included in other income (expense), net		$ 2	$ 1

Fair Value Measurements - Rec_2

Fair Value Measurements - Reconciliation of Contingent Consideration Measured at Fair Value (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of year	$ 22
Balance, end of year	130	$ 22
Recurring Measurement Basis | Contingent consideration
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of year	22	0
Purchases	106	21
Total loss included in other income (expense), net	5	1
Settlements	$ (3)	0
Balance, end of year		$ 22

Fair Value Measurements - Fair

Fair Value Measurements - Fair Value Level 3 Inputs, Quantitative Information (Details)	12 Months Ended
	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Contingent consideration	$ 130,000,000	$ 22,000,000
Energy derivative | Minimum | Discounted Cash Flow
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Forward electricity price (in dollars per MWh)	20.02	14.44
Discount rate (percent)	2.80%	1.69%
Energy derivative | Maximum | Discounted Cash Flow
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Forward electricity price (in dollars per MWh)	32.58	71.45
Discount rate (percent)	2.81%	1.96%
Energy derivative | Recurring Measurement Basis
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Energy derivative	$ 7,000,000	$ 27,000,000	$ 41,000,000
Energy derivative | Recurring Measurement Basis | Level 3
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Energy derivative	$ 7,000,000	$ 27,000,000
Congestion revenue rights | Minimum | Market Approach Valuation Technique
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Auction price (in dollars per MWh)	2.48
Congestion revenue rights | Maximum | Market Approach Valuation Technique
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Auction price (in dollars per MWh)	8.23
Congestion revenue rights | Recurring Measurement Basis | Level 3
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Energy derivative	$ 1,000,000
Contingent consideration | Discounted Cash Flow
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Annual energy production loss		1.00%
Contingent consideration | Minimum | Discounted Cash Flow
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Discount rate (percent)		4.00%
Contingent consideration | Maximum | Discounted Cash Flow
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Discount rate (percent)		8.00%
Contingent consideration | Recurring Measurement Basis
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Purchases	106,000,000	$ 21,000,000
Contingent consideration		22,000,000	$ 0
Contingent consideration | Recurring Measurement Basis | Level 3
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Contingent consideration	$ 25,000,000	$ 22,000,000
Broadview Project
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Discount rate (percent)	5.00%
Broadview Project | Contingent consideration | Discounted Cash Flow
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Annual energy production loss	0.70%
Broadview Project | Contingent consideration | Minimum | Discounted Cash Flow
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Discount rate (percent)	4.00%
Broadview Project | Contingent consideration | Maximum | Discounted Cash Flow
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Discount rate (percent)	8.00%
Tsugaru Holdings | Contingent consideration | Discounted Cash Flow
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Discount rate (percent)	6.90%
Tsugaru Holdings | Contingent consideration | Minimum | Discounted Cash Flow
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Deferred purchase price	$ 109,000,000
Tsugaru Holdings | Contingent consideration | Maximum | Discounted Cash Flow
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Deferred purchase price	128,000,000
Tsugaru Holdings | Contingent consideration | Recurring Measurement Basis | Level 3
Fair Value Measurements, Recurring and Nonrecurring, Valuation Techniques [Line Items]
Contingent consideration	$ 105,000,000

Fair Value Measurements - Carry

Fair Value Measurements - Carrying Amounts and Fair Values of Financial Liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, as reflected on balance sheets	$ 2,283	$ 1,931
Long-term debt excluding revolving credit facility
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, as reflected on balance sheets	2,283
Long-term debt, fair value	2,240	1,938
Long-term debt excluding revolving credit facility | Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	0	0
Long-term debt excluding revolving credit facility | Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	2,240	1,938
Long-term debt excluding revolving credit facility | Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt, fair value	$ 0	$ 0

Income Taxes - Components of Ta

Income Taxes - Components of Tax Provision (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Current:
Federal	$ 0	$ 0	$ 0
State	0	0	0
Foreign	16	0	0
Total current expense	16	0	0
Deferred:
Federal	0	(3)	0
State	0	0	0
Foreign	16	15	9
Total deferred expense	16	12	9
Total provision for income taxes	$ 32	$ 12	$ 9

Income Taxes - Components of In

Income Taxes - Components of Income Before Income Tax (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
U.S.	$ (158)	$ (119)	$ (71)
Foreign	121	49	28
Total	$ (37)	$ (70)	$ (43)

Income Taxes - Reconciliation o

Income Taxes - Reconciliation of Statutory Rate to Effective Rate (Details)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
Computed tax at statutory rate	21.00%	35.00%	35.00%
Adjustment for income in non-taxable entities allocable to noncontrolling interests	(125.20%)	(32.60%)	(25.60%)
Tax rate differential on pre-tax book income	(16.10%)	6.40%	0.70%
Dual taxpaying entities outside basis difference	(78.50%)	(23.00%)	(17.60%)
Local tax on branch profits/(losses)—Puerto Rico	(0.10%)	0.10%	0.00%
Permanent book/tax differences (domestic only)	0.50%	(0.10%)	(0.20%)
Valuation allowance change	38.90%	47.70%	(18.80%)
Subpart F income	(7.90%)	(3.50%)	0.00%
Capital gain exclusion - sale of partnership interest	24.70%	0.00%	0.00%
Contingent consideration accretion	(4.90%)	0.00%	0.00%
Impairment	1.40%	0.00%	0.00%
Tax credits	61.70%	31.60%	7.60%
Effect of U.S. tax rate change under Tax Cuts and Jobs Act	0.00%	(78.10%)	0.00%
Other	(2.50%)	(0.10%)	(0.90%)
Effective income tax rate	(87.00%)	(16.60%)	(19.80%)

Income Taxes - Components of De

Income Taxes - Components of Deferred Tax Assets and Deferred Tax Liabilities (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Deferred tax assets:
Accruals and prepaids	$ 3	$ 3
Basis difference in derivatives	3	0
Hatchet Ridge financing	17	17
Asset retirement obligation	32	6
Unrealized loss on derivatives	0	2
Net operating loss carryforwards	230	274
Foreign currency translation adjustments	2	3
Other deferred tax assets	12	2
Tax credits	118	42
Total gross deferred tax assets	417	349
Less: Valuation allowance	(175)	(141)
Total gross deferred tax assets net of valuation allowance	242	208
Deferred tax liabilities:
Property, plant and equipment	(215)	(189)
Intangibles	24	0
Partnership interest	(108)	(65)
Deferred interest, commitment fees and financing costs	(2)	(2)
Unrealized gain on derivatives	(2)	0
Basis difference in subsidiaries	(2)	(1)
Other deferred tax liabilities	(1)	(1)
Total gross deferred tax liabilities	(354)	(258)
Total net deferred tax assets/(liabilities)
Total net deferred tax assets/(liabilities)	$ (112)	$ (50)

Income Taxes - Additional Infor

Income Taxes - Additional Information (Details) - USD ($)	Dec. 31, 2018	Dec. 31, 2018	Dec. 31, 2017
Income Taxes [Line Items]
U.S. foreign tax credits	$ 52,000,000	$ 52,000,000
Net change in valuation allowance		34,000,000
Production tax credits	17,000,000	17,000,000
Interest expenses or penalties incurred, associated with unrecognized tax benefits		0
Outstanding liabilities associated with unrecognized tax benefits	0	$ 0
Special tax rate related to tax holiday (percent)			4.00%
Duration of tax holiday (in years)		25 years
Tax holiday impact on foreign deferred tax expense		$ 400,000
Class A Common Stock
Income Taxes [Line Items]
Tax holiday impact on net income per share of basic and diluted (in dollars per share)		$ 0.004
Domestic
Income Taxes [Line Items]
Net operating loss carryforwards	959,000,000	$ 959,000,000
State
Income Taxes [Line Items]
Net operating loss carryforwards	190,000,000	190,000,000
Canada
Income Taxes [Line Items]
Net operating loss carryforwards	31,000,000	31,000,000
Puerto Rico
Income Taxes [Line Items]
Net operating loss carryforwards	4,000,000	4,000,000
Chile
Income Taxes [Line Items]
Net operating loss carryforwards	13,000,000	$ 13,000,000
K2 Project
Income Taxes [Line Items]
Gain on sale of minority interest, net of tax	$ 12,000,000

Stockholders' Equity - Addition

Stockholders' Equity - Additional Information (Details) $ / shares in Units, $ in Millions	Oct. 23, 2017USD ($)$ / sharesshares	Aug. 22, 2016shares	Aug. 22, 2016USD ($)	Aug. 12, 2016shares	May 09, 2016USD ($)$ / shares	Dec. 31, 2018USD ($)vote$ / sharesshares	Dec. 31, 2017USD ($)$ / sharesshares	Dec. 31, 2016USD ($)
Changes In Equity And Comprehensive Income Line Items [Line Items]
Preferred stock, authorized (in shares)						100,000,000
Preferred stock, issued (in shares)						0	0
Preferred stock, outstanding (in shares)						0	0
Issuance of common stock, shares (in shares)	9,200,000	1,300,000		10,000,000
Maximum shares for over-allotment option (in shares)				1,500,000
Sale of stock, price per share (in dollars per share) | $ / shares	$ 23.40
Proceeds from public offering, net of issuance costs | $	$ 212		$ 259			$ 0	$ 237	$ 286
Common stock, par value (in dollars per share) | $ / shares					$ 0.01	$ 0.01	$ 0.01
Stock to be issued, value | $					$ 200
Shares sold under the equity distribution agreement						1,068,261	1,240,504
Net proceeds from issuances under equity distribution agreement | $						$ 25	$ 28
Aggregate compensation paid (less than $1 million) | $							$ 1	$ 1
Remaining stock available to be issued, value | $						$ 144
Number of votes per share | vote						1
Class A Common Stock | Parent Company
Changes In Equity And Comprehensive Income Line Items [Line Items]
Common stock, par value (in dollars per share) | $ / shares						$ 0.01	$ 0.01
Over-Allotment Option
Changes In Equity And Comprehensive Income Line Items [Line Items]
Issuance of common stock, shares (in shares)	1,200,000
Broadview
Changes In Equity And Comprehensive Income Line Items [Line Items]
Pay-go contribution | $						$ 4

Stockholders' Equity - Noncontr

Stockholders' Equity - Noncontrolling Interest Balances by Projects (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Noncontrolling Interest [Line Items]
Noncontrolling interests	$ 1,112	$ 1,254
El Arrayán
Noncontrolling Interest [Line Items]
Noncontrolling interests	0	32
Logan's Gap
Noncontrolling Interest [Line Items]
Noncontrolling interests	132	171
Panhandle 1
Noncontrolling Interest [Line Items]
Noncontrolling interests	131	175
Panhandle 2
Noncontrolling Interest [Line Items]
Noncontrolling interests	176	208
Post Rock
Noncontrolling Interest [Line Items]
Noncontrolling interests	116	160
Amazon Wind
Noncontrolling Interest [Line Items]
Noncontrolling interests	101	134
Broadview Project
Noncontrolling Interest [Line Items]
Noncontrolling interests	257	308
Futtsu
Noncontrolling Interest [Line Items]
Noncontrolling interests	10	0
Meikle
Noncontrolling Interest [Line Items]
Noncontrolling interests	57	66
MSM
Noncontrolling Interest [Line Items]
Noncontrolling interests	37	0
Stillwater
Noncontrolling Interest [Line Items]
Noncontrolling interests	$ 95	$ 0

Stockholders' Equity - Componen

Stockholders' Equity - Components of Noncontrolling Interest (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Stockholders' Equity Attributable to Noncontrolling Interest [Roll Forward]
Beginning balance				$ 1,254					$ 1,254
Acquisitions									49	$ 390
Contribution from noncontrolling interests									98
Distributions to noncontrolling interests									(38)	(20)	$ (18)
Partial sale of subsidiary										54
Net loss	$ 9	$ 19	$ 34	149	$ 14	$ 18	$ 29	$ 3	211	64	35
Ending balance	1,112				1,254				1,112	1,254
Tax reform, change in tax rate				150					150
Capital
Stockholders' Equity Attributable to Noncontrolling Interest [Roll Forward]
Beginning balance				1,380				954	1,380	954	972
Acquisitions									49	390
Contribution from noncontrolling interests									98
Distributions to noncontrolling interests									(38)	(20)	(18)
Partial sale of subsidiary									(37)	56
Net loss									0	0	0
Other comprehensive loss, net of tax									0	0	0
Ending balance	1,452				1,380				1,452	1,380	954
Accumulated Income (Loss)
Stockholders' Equity Attributable to Noncontrolling Interest [Roll Forward]
Beginning balance				(126)				(62)	(126)	(62)	(27)
Acquisitions									0	0
Contribution from noncontrolling interests									0
Distributions to noncontrolling interests									0	0	0
Partial sale of subsidiary									5	0
Net loss									(211)	(64)	(35)
Other comprehensive loss, net of tax									0	0	0
Ending balance	(332)				(126)				(332)	(126)	(62)
Accumulated Other Comprehensive Income (Loss)
Stockholders' Equity Attributable to Noncontrolling Interest [Roll Forward]
Beginning balance				0				(1)	0	(1)	(1)
Acquisitions									0	0
Contribution from noncontrolling interests									0
Distributions to noncontrolling interests									0	0	0
Partial sale of subsidiary									0	0
Net loss									0	0	0
Other comprehensive loss, net of tax									(8)	1	0
Ending balance	(8)				0				(8)	0	(1)
Noncontrolling Interests
Stockholders' Equity Attributable to Noncontrolling Interest [Roll Forward]
Beginning balance				$ 1,254				$ 891	1,254	891	944
Acquisitions									49	390
Contribution from noncontrolling interests									98
Distributions to noncontrolling interests									(38)	(20)	(18)
Partial sale of subsidiary									(32)	56
Net loss									(211)	(64)	(35)
Other comprehensive loss, net of tax									(8)	1	0
Ending balance	$ 1,112				$ 1,254				$ 1,112	$ 1,254	$ 891

Equity Incentive Award Plan - W

Equity Incentive Award Plan - Weighted Average Assumptions (Details) - TSR-RSAs	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected volatility (percent)	32.00%	34.00%	35.00%
Risk-free interest rate (percent)	2.38%	1.60%	1.11%
Expected life (in years)	2 years 9 months 20 days	2 years 9 months 20 days	2 years 9 months 20 days

Equity Incentive Award Plan - S

Equity Incentive Award Plan - Summary of Restricted Stock Awards Activity (Details) - $ / shares	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
RSUs
Shares
Granted (shares)	25,885
Ending balance (in shares)	0
Weighted-Average Grant-Date Fair Value
Granted (in dollars per share)	$ 21.49	$ 18.99	$ 20.29
RSAs
Shares
Beginning balance (in shares)	110,579
Granted (shares)	138,817
Vested (shares)	(127,268)
Ending balance (in shares)	122,128	110,579
Weighted-Average Grant-Date Fair Value
Beginning balance (in dollars per share)	$ 19.26
Granted (in dollars per share)	18.67	$ 20.35	18.76
Vested (in dollars per share)	19.03
Ending balance (in dollars per share)	$ 18.84	$ 19.26
TSR-RSAs
Shares
Beginning balance (in shares)	218,877
Granted (shares)	97,610
Vested (shares)		(56,844)
Ending balance (in shares)	259,643	218,877
Weighted-Average Grant-Date Fair Value
Beginning balance (in dollars per share)	$ 25.07
Granted (in dollars per share)	18.20	$ 19.48	$ 20.63
Vested (in dollars per share)	39.16
Ending balance (in dollars per share)	$ 19.40	$ 25.07

Equity Incentive Award Plan - A

Equity Incentive Award Plan - Additional Information (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares authorized to be issued under plan (in shares)	3,000,000
Stock-based compensation expense	$ 5	$ 5	$ 5
Exercises in the period (in shares)	0	0	0
Grants in the period (in shares)	0	0	0
Class A Common Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares available for grant (in shares)	1,780,006
TSR-RSAs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted average grant date fair value of grants in period (in dollars per share)	$ 18.20	$ 19.48	$ 20.63
Unrecorded stock-based compensation expense	$ 2
Unrecorded stock-based compensation expense period of amortization (in years)	21 months
Performance period	3 years
Granted (shares)	97,610
Restricted stock awards unvested (in shares)	259,643	218,877
RSAs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair value of restricted stock awards vested	$ 3	$ 3	$ 2
Weighted average grant date fair value of grants in period (in dollars per share)	$ 18.67	$ 20.35	$ 18.76
Unrecorded stock-based compensation expense	$ 2
Unrecorded stock-based compensation expense period of amortization (in years)	20 months
Granted (shares)	138,817
Restricted stock awards unvested (in shares)	122,128	110,579
RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair value of restricted stock awards vested		$ 1	$ 1
Weighted average grant date fair value of grants in period (in dollars per share)	$ 21.49	$ 18.99	$ 20.29
Granted (shares)	25,885
Restricted stock awards unvested (in shares)	0

Equity Incentive Award Plan -_2

Equity Incentive Award Plan - Stock Option Activity (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Shares
Beginning balance (in shares)	411,323
Option forfeited and expired (shares)	29,169
Ending balance (in shares)	382,154	411,323
Exercisable (in shares)	382,154
Weighted-Average Exercise Price
Weighted-average exercise price, outstanding (in dollars per share)		$ 22
Weighted-average exercise price, forfeited or expired (in dollars per share)		$ 22
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Weighted average remaining contractual life, outstanding	4 years 8 months 20 days
Weighted average remaining contractual life, exercisable	4 years 8 months 20 days
Aggregate intrinsic value, outstanding	$ 0
Aggregate intrinsic value, exercisable	$ 0

Earnings (Loss) Per Share (Deta

Earnings (Loss) Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Earnings Per Share [Line Items]
Potentially dilutive securities excluded from earnings per share calculation (shares)									9,000,000	9,000,000	8,000,000
Numerator for basic and diluted earnings (loss) per share:
Net income (loss) attributable to Pattern Energy	$ (13,000)	$ (13,000)	$ 32,000	$ 136,000	$ (8,000)	$ (30,000)	$ 14,000	$ 6,000	$ 142,000	$ (18,000)	$ (17,000)
Less: earnings allocated to participating securities									(169)	(104)	(53)
Net income (loss) attributable to common stockholders									$ 142,000	$ (18,000)	$ (17,000)
Denominator for earnings (loss) per share:
Diluted (in shares)									97,651,501	89,179,343	79,382,388
Earnings (loss) per share:
Basic loss per share (in dollars per share)	$ (0.15)	$ (0.13)	$ 0.34	$ 1.39					$ 1.45	$ (0.20)	$ (0.22)
Dividends declared (in dollars per share)	$ 0.4220	$ 0.4220	$ 0.4220	$ 0.4220	$ 0.4220	$ 0.42	$ 0.4180	$ 0.4138
Class A Common Stock
Denominator for earnings (loss) per share:
Weighted average number of shares - Basic and diluted (in shares)									97,456,407	89,179,343	79,382,388
Earnings (loss) per share:
Basic loss per share (in dollars per share)											$ (0.22)
Dividends declared (in dollars per share)									$ 1.69	$ 1.6747	$ 1.58
Restricted Stock
Denominator for earnings (loss) per share:
Dilutive effect (in shares)									193,910	0	0
RSUs
Denominator for earnings (loss) per share:
Dilutive effect (in shares)									1,184	0	0

Commitments and Contingencies -

Commitments and Contingencies - Schedule of Future Commitments (Details) $ in Millions	Dec. 31, 2018USD ($)
Transmission service agreements
2,019	$ 24
2,020	24
2,021	24
2,022	24
2,023	24
Thereafter	495
Total	615
Operating leases
2,019	22
2,020	21
2,021	22
2,022	21
2,023	22
Thereafter	352
Total	460
Total commitments
2,019	270
2,020	230
2,021	80
2,022	75
2,023	75
Thereafter	949
Total	1,679
Service and maintenance agreements
Service and maintenance agreements
2,019	32
2,020	30
2,021	30
2,022	27
2,023	26
Thereafter	68
Total	213
Construction and other commitments
Service and maintenance agreements
2,019	192
2,020	155
2,021	4
2,022	3
2,023	3
Thereafter	34
Total	$ 391

Commitments and Contingencies_2

Commitments and Contingencies - Additional Information (Details) - USD ($) $ in Millions	1 Months Ended	12 Months Ended
	Sep. 30, 2018	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Mar. 31, 2018
Other Commitments [Line Items]
Total operating lease payments		$ 460
Annual inflation price adjustment percentage		2.00%
Maintenance costs		$ 38	$ 47	$ 53
Power Sale Agreements
Other Commitments [Line Items]
Letters-of-credit outstanding		156
Project Finance Agreements
Other Commitments [Line Items]
Letters-of-credit outstanding		170
Turbine manufacturers
Other Commitments [Line Items]
Turbine availability bonus payable		1
Transmission Service Agreement
Other Commitments [Line Items]
Operating lease cost		$ 25
Service and maintenance agreements
Other Commitments [Line Items]
Agreement term (in years)		22 years
Minimum
Other Commitments [Line Items]
Term of contract		1 year
Minimum | Power Sale Agreements
Other Commitments [Line Items]
Termination date		2,019
Minimum | Transmission Service Agreement
Other Commitments [Line Items]
Term of contract		3 years
Maximum
Other Commitments [Line Items]
Term of contract		40 years
Maximum | Power Sale Agreements
Other Commitments [Line Items]
Termination date		2,043
Maximum | Transmission Service Agreement
Other Commitments [Line Items]
Term of contract		29 years
Land (lease)
Other Commitments [Line Items]
Rent expense		$ 18	$ 15	$ 13
Operating Lease, Corporate Headquarters, San Francisco, CA
Other Commitments [Line Items]
Total operating lease payments					$ 35
Broadview Project
Other Commitments [Line Items]
Discount rate (percent)		5.00%
Undiscounted contingent obligation		$ 50
Continued Operation Of Broadview | Broadview Project
Other Commitments [Line Items]
Contingent liability		7
Continued Operation Of Grady | Broadview Project
Other Commitments [Line Items]
Contingent liability		29
Panhandle 2
Other Commitments [Line Items]
Turbine availability bonus payable		4
Panhandle 2 | Maximum
Other Commitments [Line Items]
Turbine availability bonus payable		$ 5
Gulf Wind Re-Powering Commitment
Other Commitments [Line Items]
Maximum purchase price	$ 151
Interest in Western Interconnect by third party
Other Commitments [Line Items]
Ownership percentage		1.00%

Related Party Transactions - Ad

Related Party Transactions - Additional Information (Details) - USD ($) shares in Millions, $ in Millions	Jun. 16, 2017	Sep. 30, 2018	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Jun. 30, 2017
Related Party Transaction [Line Items]
Defined contribution plan, contributions			$ 1	$ 1	$ 1
Purchase amount			23
Pattern Development 2.0
Related Party Transaction [Line Items]
Investment in related party			115
Aggregate cost			$ 183
Ownership interest (percent)			29.00%
Tsugaru
Related Party Transaction [Line Items]
Development fee		$ 15
PSP
Related Party Transaction [Line Items]
Maximum aggregate amount of co-investment						$ 500
Shares purchased (in shares)			0.6
MSM | PSP
Related Party Transaction [Line Items]
Ownership percentage			49.00%
Stillwater | PSP
Related Party Transaction [Line Items]
Ownership percentage			49.00%
Meikle | Panhandle 2 Holdings
Related Party Transaction [Line Items]
Ownership percentage			49.00%
Meikle | PSP
Related Party Transaction [Line Items]
Ownership percentage			49.00%
Pattern Development 1.0 | PSP
Related Party Transaction [Line Items]
Shares purchased (in shares)	9

Related Party Transactions - Re

Related Party Transactions - Related Party Receivable and Payable (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017
Related Party Transaction [Line Items]
Due from related parties	$ 7	$ 13
Due to related parties	139	32
Other current assets
Related Party Transaction [Line Items]
Due from related parties	7	13
Other current liabilities
Related Party Transaction [Line Items]
Due to related parties	9	11
Contingent liabilities, current
Related Party Transaction [Line Items]
Due to related parties	25	0
Contingent liabilities
Related Party Transaction [Line Items]
Due to related parties	$ 105	$ 21

Related Party Transactions - _2

Related Party Transactions - Related Party Revenue and Expense Included in Combined Statement of Operations (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Related Party Transaction [Line Items]
Other revenue	$ 9	$ 8	$ 6
General and administrative	12	12	5
Related party general and administrative expense	(15)	(14)	(10)
Project Expense
Related Party Transaction [Line Items]
Other revenue	$ 1	$ 0	$ 0

Related Party Transactions - _3

Related Party Transactions - Related Party Purchase Agreements (Details) - USD ($) $ in Millions	Nov. 20, 2018	Mar. 07, 2018	Aug. 10, 2017	Apr. 21, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Aug. 10, 2018
Related Party Transaction [Line Items]
Cash consideration net of acquired cash					$ 415	$ 297	$ 136
Japan projects
Related Party Transaction [Line Items]
Cash consideration net of acquired cash		$ 158
Debt Assumed		181
Contingent consideration		$ 106
MSM
Related Party Transaction [Line Items]
Cash consideration net of acquired cash			$ 31
Debt Assumed								$ 196
Contingent consideration								$ 0
Stillwater
Related Party Transaction [Line Items]
Cash consideration net of acquired cash	$ 17
Debt Assumed	0
Contingent consideration	$ 0
Broadview Project
Related Party Transaction [Line Items]
Cash consideration net of acquired cash				$ 169
Debt Assumed				51
Contingent consideration				$ 21
Meikle
Related Party Transaction [Line Items]
Cash consideration net of acquired cash			58
Debt Assumed			266
Contingent consideration			$ 0

Segment Reporting - Additional

Segment Reporting - Additional Information (Details) - segment	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Segment Reporting [Abstract]
Number of reportable segments	2	1

Segment Reporting - Schedule of

Segment Reporting - Schedule of Segment Information (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Segment Reporting Information [Line Items]
Revenue	$ 113	$ 118	$ 140	$ 112	$ 110	$ 92	$ 108	$ 101	$ 483	$ 411	$ 354
Depreciation, amortization and accretion									250	199	175
Impairment expense									7	0	0
Operating income (loss)									2	10	5
Earnings in unconsolidated investments, net									1	42	30
Interest expense									109	102	78
Income tax provision									32	12	9
Net loss	(22)	$ (32)	$ (2)	$ (13)	(22)	$ (48)	$ (15)	$ 3	(69)	(82)	(52)
Capital expenditures									(181)	(44)	$ (33)
Property, plant and equipment, net	4,119				3,965				4,119	3,965
Unconsolidated investments	270				311				270	311
Total assets	5,294				$ 4,742				5,294	$ 4,742
Operating Segments | Operating Business
Segment Reporting Information [Line Items]
Revenue									475
Depreciation, amortization and accretion									247
Impairment expense									0
Operating income (loss)									45
Earnings in unconsolidated investments, net									41
Interest expense									63
Income tax provision									11
Net loss									(38)
Adjusted EBITDA									391
Capital expenditures									(175)
Property, plant and equipment, net	4,054								4,054
Unconsolidated investments	228								228
Total assets	8,990								8,990
Operating Segments | Development Investment
Segment Reporting Information [Line Items]
Revenue									39
Depreciation, amortization and accretion									0
Impairment expense									11
Operating income (loss)									(33)
Earnings in unconsolidated investments, net									1
Interest expense									1
Income tax provision									1
Net loss									(35)
Adjusted EBITDA									(22)
Capital expenditures									(61)
Property, plant and equipment, net	2								2
Unconsolidated investments	10								10
Total assets	187								187
Corporate, Other and Eliminations
Segment Reporting Information [Line Items]
Revenue									8
Depreciation, amortization and accretion									3
Impairment expense									7
Operating income (loss)									(43)
Earnings in unconsolidated investments, net									(40)
Interest expense									46
Income tax provision									21
Net loss									(31)
Adjusted EBITDA									(19)
Capital expenditures									(6)
Property, plant and equipment, net	65								65
Unconsolidated investments	42								42
Total assets	(3,696)								(3,696)
Loss related to portion of loss of Pattern Development									35
Intra-entity profits									5
Reconciling Amounts
Segment Reporting Information [Line Items]
Revenue									(39)
Depreciation, amortization and accretion									0
Impairment expense									(11)
Operating income (loss)									33
Earnings in unconsolidated investments, net									(1)
Interest expense									(1)
Income tax provision									(1)
Net loss									35
Adjusted EBITDA									22
Capital expenditures									61
Property, plant and equipment, net	(2)								(2)
Unconsolidated investments	(10)								(10)
Total assets	$ (187)								$ (187)

Segment Reporting - Reconciliat

Segment Reporting - Reconciliation of Segment Adjusted EBITDA (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Segment Reporting Information [Line Items]
Earnings in unconsolidated investments, net									$ 1	$ 42	$ 30
Unrealized loss derivatives									(5)
Early extinguishment of debt									(6)	(9)	0
Impairment expense									(7)	0	0
Other									(2)
Gain on asset sales									71
Interest expense, net of interest income									(107)
Depreciation, amortization and accretion									(280)	(215)	(189)
Net income (loss) before income tax									(37)	(70)	(43)
Income tax provision									(32)	(12)	(9)
Net loss	$ (22)	$ (32)	$ (2)	$ (13)	$ (22)	$ (48)	$ (15)	$ 3	(69)	$ (82)	$ (52)
Operating Segments | Operating Business
Segment Reporting Information [Line Items]
Adjusted EBITDA									391
Earnings in unconsolidated investments, net									41
Impairment expense									0
Income tax provision									(11)
Net loss									(38)
Operating Segments | Development Investment
Segment Reporting Information [Line Items]
Adjusted EBITDA									(22)
Earnings in unconsolidated investments, net									1
Impairment expense									(11)
Income tax provision									(1)
Net loss									(35)
Corporate, Other and Eliminations
Segment Reporting Information [Line Items]
Adjusted EBITDA									(19)
Earnings in unconsolidated investments, net									(40)
Impairment expense									(7)
Income tax provision									(21)
Net loss									(31)
Reconciling Amounts
Segment Reporting Information [Line Items]
Adjusted EBITDA									22
Earnings in unconsolidated investments, net									(1)
Impairment expense									11
Income tax provision									1
Net loss									35
Interest expense, net of interest income
Segment Reporting Information [Line Items]
Earnings in unconsolidated investments, net									(38)
Income tax provision
Segment Reporting Information [Line Items]
Earnings in unconsolidated investments, net									(1)
Depreciation, amortization and accretion
Segment Reporting Information [Line Items]
Earnings in unconsolidated investments, net									(35)
Gain on derivatives
Segment Reporting Information [Line Items]
Earnings in unconsolidated investments, net									$ 1

Selected Quarterly Financial _3

Selected Quarterly Financial Data (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Quarterly Financial Information Disclosure [Abstract]
Revenue	$ 113	$ 118	$ 140	$ 112	$ 110	$ 92	$ 108	$ 101	$ 483	$ 411	$ 354
Gross profit (loss)	(14)	20	44	14	16	(2)	21	28	64	63	50
Net loss	(22)	(32)	(2)	(13)	(22)	(48)	(15)	3	(69)	(82)	(52)
Net loss attributable to noncontrolling interests	(9)	(19)	(34)	(149)	(14)	(18)	(29)	(3)	(211)	(64)	(35)
Net income (loss) attributable to Pattern Energy	$ (13)	$ (13)	$ 32	$ 136	$ (8)	$ (30)	$ 14	$ 6	$ 142	$ (18)	$ (17)
Earnings (loss) per share:
Basic (in dollars per share)	$ (0.15)	$ (0.13)	$ 0.34	$ 1.39					$ 1.45	$ (0.20)	$ (0.22)
Diluted (in dollars per share)	(0.15)	(0.13)	0.34	1.32					$ 1.45	$ (0.20)	$ (0.22)
Basic and diluted earnings (loss) per share—Class A common stock (in dollars per share)					$ (0.08)	$ (0.34)	$ 0.16	$ 0.06
Dividends declared (in dollars per share)	$ 0.4220	$ 0.4220	$ 0.4220	$ 0.4220	$ 0.4220	$ 0.42	$ 0.4180	$ 0.4138
Tax reform, change in tax rate				$ 150					$ 150

Subsequent Events (Details)

Subsequent Events (Details) $ / shares in Units, $ in Millions	Feb. 22, 2019$ / shares	Jan. 29, 2019USD ($)MW	Nov. 06, 2018MW	Dec. 31, 2018GW
Subsequent Event [Line Items]
Power generation capacity (in MW)			90	4
Subsequent Event
Subsequent Event [Line Items]
Dividends payable (in dollars per share)	$ 0.4220
Dividends payable annualized (in dollars per share)	$ 1.688
Hatchet Ridge Wind LLC | Subsequent Event
Subsequent Event [Line Items]
Power generation capacity (in MW) | MW		101
Net long-lived assets | $		$ 138

Schedule I-Condensed Parent-C_2

Schedule I-Condensed Parent-Company Financial Statements - Balance Sheets (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Current assets:
Cash and cash equivalents	$ 101	$ 117	$ 84
Derivative assets, current	14	19
Other current assets	16	21
Total current assets	211	270
Property, plant and equipment, net	4,119	3,965
Unconsolidated investments	270	311
Derivative assets	9	10
Intangible assets, net	219	136
Other assets	34	24
Total assets	5,294	4,742
Current liabilities:
Accounts payable and other accrued liabilities	67	54
Accrued interest	14	17
Dividend payable	42	41
Derivative liabilities, current	2	8
Contingent liabilities, current	31	3
Other current liabilities	11	12
Total current liabilities	478	218
Long-term debt, net of financing costs of $7 and $9 as of December 31, 2018 and 2017, respectively	2,004	1,879
Other long-term liabilities	71	50
Total liabilities	3,135	2,394
Equity:
Class A common stock, $0.01 par value per share: 500,000,000 shares authorized; 98,051,629 and 97,860,048 shares outstanding as of December 31, 2018 and December 31, 2017, respectively	1	1
Additional paid-in capital	1,130	1,235
Accumulated income (loss)	(27)	(112)
Accumulated other comprehensive loss	(52)	(26)
Treasury stock, at cost; 223,040 and 157,812 shares of Class A common stock as of December 31, 2018 and 2017, respectively	(5)	(4)
Total equity	2,159	2,348	1,879	$ 1,776
Total liabilities and equity	5,294	4,742
Parent Company
Current assets:
Cash and cash equivalents	3	9	$ 12
Derivative assets, current	4	0
Other current assets	17	26
Total current assets	24	35
Property, plant and equipment, net	2	4
Investments in subsidiaries	1,415	1,404
Unconsolidated investments	270	311
Derivative assets	1	0
Intangible assets, net	1	1
Other assets	1	1
Total assets	1,714	1,756
Current liabilities:
Accounts payable and other accrued liabilities	13	12
Accrued interest	13	13
Dividend payable	42	41
Derivative liabilities, current	0	3
Contingent liabilities, current	29	0
Other current liabilities	3	9
Total current liabilities	100	78
Long-term debt, net of financing costs of $7 and $9 as of December 31, 2018 and 2017, respectively	560	553
Other long-term liabilities	7	32
Total liabilities	667	663
Equity:
Additional paid-in capital	1,103	1,207
Accumulated income (loss)	0	(85)
Accumulated other comprehensive loss	(52)	(26)
Total equity	1,047	1,093
Total liabilities and equity	1,714	1,756
Parent Company | Class A Common Stock
Equity:
Class A common stock, $0.01 par value per share: 500,000,000 shares authorized; 98,051,629 and 97,860,048 shares outstanding as of December 31, 2018 and December 31, 2017, respectively	1	1
Treasury stock, at cost; 223,040 and 157,812 shares of Class A common stock as of December 31, 2018 and 2017, respectively	$ (5)	$ (4)

Schedule I-Condensed Parent-C_3

Schedule I-Condensed Parent-Company Financial Statements - Balance Sheets (Parenthetical) (Details) - USD ($) $ / shares in Units, $ in Millions	Dec. 31, 2018	Dec. 31, 2017	May 09, 2016
Condensed Balance Sheet Statements, Captions [Line Items]
Unamortized financing costs	$ 21	$ 23
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	500,000,000	500,000,000
Common stock, shares outstanding (in shares)	98,051,629	97,860,048
Treasury stock, shares (in shares)	223,040	157,812
Parent Company
Condensed Balance Sheet Statements, Captions [Line Items]
Unamortized financing costs	$ (7)	$ (9)
Treasury stock, shares (in shares)	223,040	157,812
Parent Company | Class A Common Stock
Condensed Balance Sheet Statements, Captions [Line Items]
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized (in shares)	500,000,000	500,000,000
Common stock, shares outstanding (in shares)	98,051,629	97,860,048

Schedule I-Condensed Parent-C_4

Schedule I-Condensed Parent-Company Financial Statements - Statements of Operations and Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Condensed Income Statements, Captions [Line Items]
Revenue	$ 113	$ 118	$ 140	$ 112	$ 110	$ 92	$ 108	$ 101	$ 483	$ 411	$ 354
Expenses									62	53	45
Operating income									2	10	5
Other income (expense):
Interest expense									(109)	(102)	(78)
Earnings in unconsolidated investments, net									1	42	30
Gain (loss) on derivatives									17	(10)	(3)
Total other expense									(39)	(80)	(48)
Net income (loss) before income tax									(37)	(70)	(43)
Tax provision (benefit)									(32)	(12)	(9)
Net loss	$ (22)	$ (32)	$ (2)	$ (13)	$ (22)	$ (48)	$ (15)	$ 3	(69)	(82)	(52)
Other comprehensive income (loss), net of tax
Proportionate share of affiliates' other comprehensive income (loss) activity, net of tax provision of less than $(1), $(5) and $(2), respectively									2	14	6
Total other comprehensive income (loss), net of tax									(34)	37	11
Comprehensive income (loss) attributable to Pattern Energy									116	18	(6)
Parent Company
Condensed Income Statements, Captions [Line Items]
Revenue									0	0	0
Expenses									35	34	34
Operating income									(35)	(34)	(34)
Other income (expense):
Interest expense									(37)	(35)	(15)
Equity in earnings from subsidiaries									203	14	3
Earnings in unconsolidated investments, net									1	41	30
Gain (loss) on derivatives									10	(7)	(1)
Other income (expense), net									(1)	(1)	0
Total other expense									176	12	17
Net income (loss) before income tax									141	(22)	(17)
Tax provision (benefit)									0	4	0
Net loss									141	(18)	(17)
Other comprehensive income (loss), net of tax
Proportionate share of subsidiaries' other comprehensive income (loss), net of tax benefit (provision) of $2, $(5) and less than $(1), respectively									(27)	23	5
Proportionate share of affiliates' other comprehensive income (loss) activity, net of tax provision of less than $(1), $(5) and $(2), respectively									1	13	6
Total other comprehensive income (loss), net of tax									(26)	36	11
Comprehensive income (loss) attributable to Pattern Energy									$ 115	$ 18	$ (6)

Schedule I-Condensed Parent-C_5

Schedule I-Condensed Parent-Company Financial Statements - Statements of Operations and Comprehensive Income (Loss) (Parenthetical) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Condensed Income Statements, Captions [Line Items]
Proportionate share of equity investee's other comprehensive (loss) income activity, net of tax benefit (provision) (less than $1 million)	$ (1)	$ 5	$ 2
Parent Company
Condensed Income Statements, Captions [Line Items]
Proportionate share of subsidiaries’ other comprehensive (loss) income activity, tax (less than $1 million)	2	(5)	(1)
Proportionate share of equity investee's other comprehensive (loss) income activity, net of tax benefit (provision) (less than $1 million)	$ (1)	$ (5)	$ (2)

Schedule I-Condensed Parent-C_6

Schedule I-Condensed Parent-Company Financial Statements - Statements of Cash Flows (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Operating activities
Net loss	$ (22)	$ (32)	$ (2)	$ (13)	$ (22)	$ (48)	$ (15)	$ 3	$ (69)	$ (82)	$ (52)
Adjustments to reconcile net (loss) income to net cash used in operating activities:
Depreciation, amortization and accretion									280	215	189
Amortization of debt discount									5	5	4
Deferred taxes									16	15	8
Loss on derivatives									4	16	22
Stock-based compensation									5	5	5
Equity in earnings from unconsolidated investments, net									(1)	(42)	(30)
Other reconciling items									1	(5)	(4)
Changes in operating assets and liabilities:
Other current assets									15	(14)	(4)
Accounts payable and other accrued liabilities									3	18	(3)
Other current liabilities									26	15	2
Other long-term liabilities									(20)	21	7
Net cash provided by operating activities									279	218	164
Investing activities
Capital expenditures									(181)	(44)	(33)
Other assets										8	3
Other assets									(1)
Net cash used in investing activities									(373)	(320)	(124)
Financing activities
Dividends paid									(165)	(145)	(120)
Other financing activities									(4)	(6)	(2)
Net cash provided by (used in) financing activities									83	125	(77)
Net change in cash, cash equivalents and restricted cash									(15)	29	(37)
Cash, cash equivalents and restricted cash at beginning of period				138				109	138	109	146
Cash, cash equivalents and restricted cash at end of period	123				138				123	138	109
Schedule of non-cash activities
Cash payments for interest expense									97	86	70
Change in property, plant and equipment									224	2	1
Parent Company
Operating activities
Net loss									141	(18)	(17)
Adjustments to reconcile net (loss) income to net cash used in operating activities:
Depreciation, amortization and accretion									11	7	6
Deferred taxes									0	3	0
Intraperiod tax allocation									0	(3)	0
Loss on derivatives									(10)	5	3
Stock-based compensation									5	5	5
Equity in earnings from subsidiaries									(203)	(14)	(3)
Equity in earnings from unconsolidated investments, net									(1)	(41)	(30)
Other reconciling items									3	0	(1)
Changes in operating assets and liabilities:
Other current assets									0	(20)	(2)
Accounts payable and other accrued liabilities									0	3	2
Other current liabilities									29	8	0
Other long-term liabilities									(28)	1	4
Related party receivable/payable									(2)	0	0
Accrued interest payable									0	8	0
Net cash provided by operating activities									(51)	(56)	(33)
Investing activities
Capital expenditures									(3)	0	(4)
Distributions received from subsidiaries									818	372	308
Contribution to subsidiaries									(490)	(682)	(450)
Investment in Pattern Development									(115)	(69)	0
Other assets									2
Other assets										(1)	(1)
Net cash used in investing activities									212	(380)	(147)
Financing activities
Proceeds from public offering, net of issuance costs									0	237	286
Proceeds from issuance of senior notes, net of issuance costs									0	343	0
Repurchase of shares for employee tax withholding									(1)	0	0
Dividends paid									(166)	(145)	(120)
Other financing activities									0	(2)	(1)
Net cash provided by (used in) financing activities									(167)	433	165
Net change in cash, cash equivalents and restricted cash									(6)	(3)	(15)
Cash, cash equivalents and restricted cash at beginning of period				$ 9				$ 12	9	12	27
Cash, cash equivalents and restricted cash at end of period	$ 3				$ 9				3	9	12
Schedule of non-cash activities
Cash payments for interest expense									30	20	9
Change in property, plant and equipment									(5)	0	0
Non-cash increase in additional paid-in capital									$ 0	$ (2)	$ 0

Schedule I-Condensed Parent-C_7

Schedule I-Condensed Parent-Company Financial Statements - Cash Reconciliation (Details) - USD ($) $ in Millions	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Condensed Financial Statements, Captions [Line Items]
Cash and cash equivalents	$ 101	$ 117	$ 84
Parent Company
Condensed Financial Statements, Captions [Line Items]
Cash and cash equivalents	$ 3	$ 9	$ 12

Schedule I-Condensed Parent-C_8

Schedule I-Condensed Parent-Company Financial Statements - Narrative (Details)	Jul. 31, 2015$ / shares	Jan. 31, 2017USD ($)	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)	Mar. 31, 2018USD ($)
Condensed Financial Statements, Captions [Line Items]
Total operating lease payments			$ 460,000,000
Parent Company
Condensed Financial Statements, Captions [Line Items]
Total operating lease payments			67,000,000
Operating Lease, Corporate Headquarters, San Francisco, CA
Condensed Financial Statements, Captions [Line Items]
Total operating lease payments					$ 35,000,000
Operating Lease, Corporate Headquarters, San Francisco, CA | Parent Company
Condensed Financial Statements, Captions [Line Items]
Total operating lease payments			$ 35,000,000
Unsecured Debt | Parent Company
Condensed Financial Statements, Captions [Line Items]
Face amount		$ 350,000,000
Net proceeds from issuance of unsecured senior notes		$ 345,000,000
Interest rate (percent)		5.875%
Convertible Debt
Condensed Financial Statements, Captions [Line Items]
Conversion ratio (shares per $1000 of debt)			35.8997
Convertible Debt | Parent Company
Condensed Financial Statements, Captions [Line Items]
Face amount			$ 225,000,000	$ 225,000,000
Interest rate (percent)	4.00%
Conversion ratio (shares per $1000 of debt)	35.4925			35.8997
Conversion price (in dollars per share) | $ / shares	$ 28.175
Dividend threshold trigger (in dollars per share) | $ / shares	$ 0.363
Equity issuance costs			$ 1,000,000

Schedule I-Condensed Parent-C_9

Schedule I-Condensed Parent-Company Financial Statements - Convertible Debt (Details) - Convertible Debt - Parent Company - USD ($)	Dec. 31, 2018	Dec. 31, 2017
Condensed Financial Statements, Captions [Line Items]
Principal	$ 225,000,000	$ 225,000,000
Unamortized debt discount	(8,000,000)	(13,000,000)
Unamortized financing costs	(2,000,000)	(3,000,000)
Carrying value of convertible senior notes	215,000,000	209,000,000
Carrying value of the equity component	$ 24,000,000	$ 24,000,000

Schedule I-Condensed Parent-_10

Schedule I-Condensed Parent-Company Financial Statements - Commitments and Contingencies (Details) $ in Millions	Dec. 31, 2018USD ($)
Condensed Financial Statements, Captions [Line Items]
2,019	$ 22
2,020	21
2,021	22
2,022	21
2,023	22
Thereafter	352
Total	460
Parent Company
Condensed Financial Statements, Captions [Line Items]
2,019	7
2,020	7
2,021	8
2,022	7
2,023	8
Thereafter	30
Total	$ 67