Financial instruments - Fair Value of Financial Instruments (Detail) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020
Fair Value of Financial Instruments [Line Items]
Note payable to related party	$ 0	$ 30,493
Level 1
Fair Value of Financial Instruments [Line Items]
Long-term investments carried at fair value	1,824,899	1,708,683
Total financial assets	1,824,899	1,708,683
Long-term debt	2,488,347	2,316,586
Convertible debentures	433	623
Total financial liabilities	2,488,780	2,317,209
Level 2
Fair Value of Financial Instruments [Line Items]
Long-term investments carried at fair value	0	20,015
Development loans and other receivables	9,299	31,088
Derivative Asset	8,488	194
Total financial assets	17,787	51,297
Long-term debt	4,586,832	2,823,473
Note payable to related party		30,493
Convertible debentures	0
Derivative financial instruments, liabilities	64,844	104,481
Total financial liabilities	4,666,887	2,974,012
Level 2 \| Interest rate swaps \| Designated as a hedge
Fair Value of Financial Instruments [Line Items]
Derivative Asset	2,365
Derivative financial instruments, liabilities	9,124	19,649
Level 2 \| Commodity contracts for regulatory operations
Fair Value of Financial Instruments [Line Items]
Derivative Asset	2,406	194
Derivative financial instruments, liabilities		614
Level 2 \| Cross currency swap
Fair Value of Financial Instruments [Line Items]
Derivative Asset	3,717
Level 2 \| Cross currency swap \| Designated as a hedge \| Net Investment Hedging
Fair Value of Financial Instruments [Line Items]
Derivative financial instruments, liabilities	55,720	84,218
Level 2 \| Series C Preferred Stock
Fair Value of Financial Instruments [Line Items]
Preferred shares, Series C	15,211	15,565
Level 3
Fair Value of Financial Instruments [Line Items]
Long-term investments carried at fair value	104,229	110,514
Development loans and other receivables	0	0
Derivative Asset	23,773	51,913
Total financial assets	128,002	162,427
Derivative financial instruments, liabilities	17,911	5,929
Total financial liabilities	17,911	5,929
Level 3 \| Energy contracts \| Designated as a hedge \| Cash flow hedge
Fair Value of Financial Instruments [Line Items]
Derivative Asset	23,494	51,525
Derivative financial instruments, liabilities	15,384	5,597
Level 3 \| Energy contracts \| Not designated as a hedge
Fair Value of Financial Instruments [Line Items]
Derivative Asset	279
Derivative financial instruments, liabilities	2,527
Level 3 \| Energy contracts \| Not designated as a hedge \| Cash flow hedge
Fair Value of Financial Instruments [Line Items]
Derivative Asset		388
Derivative financial instruments, liabilities		332
Level 3 \| Commodity contracts for regulatory operations
Fair Value of Financial Instruments [Line Items]
Derivative Asset	0
Carrying amount
Fair Value of Financial Instruments [Line Items]
Long-term investments carried at fair value	1,929,128	1,839,212
Development loans and other receivables	7,962	23,804
Derivative Asset	32,261	52,107
Total financial assets	1,969,351	1,915,123
Long-term debt	6,622,363	4,538,470
Note payable to related party		30,493
Convertible debentures	285	295
Derivative financial instruments, liabilities	82,755	110,410
Total financial liabilities	6,719,271	4,693,366
Carrying amount \| Energy contracts \| Designated as a hedge \| Cash flow hedge
Fair Value of Financial Instruments [Line Items]
Derivative Asset	23,494	51,525
Derivative financial instruments, liabilities	15,384	5,597
Carrying amount \| Energy contracts \| Not designated as a hedge
Fair Value of Financial Instruments [Line Items]
Derivative Asset	279
Derivative financial instruments, liabilities	2,527
Carrying amount \| Energy contracts \| Not designated as a hedge \| Cash flow hedge
Fair Value of Financial Instruments [Line Items]
Derivative Asset		388
Derivative financial instruments, liabilities		332
Carrying amount \| Interest rate swaps \| Designated as a hedge
Fair Value of Financial Instruments [Line Items]
Derivative Asset	2,365
Derivative financial instruments, liabilities	9,124	19,649
Carrying amount \| Commodity contracts for regulatory operations
Fair Value of Financial Instruments [Line Items]
Derivative Asset	2,406	194
Derivative financial instruments, liabilities		614
Carrying amount \| Cross currency swap
Fair Value of Financial Instruments [Line Items]
Derivative Asset	3,717
Carrying amount \| Cross currency swap \| Designated as a hedge \| Net Investment Hedging
Fair Value of Financial Instruments [Line Items]
Derivative financial instruments, liabilities	55,720	84,218
Carrying amount \| Series C Preferred Stock
Fair Value of Financial Instruments [Line Items]
Preferred shares, Series C	13,868	13,698
Fair value
Fair Value of Financial Instruments [Line Items]
Long-term investments carried at fair value	1,929,128	1,839,212
Development loans and other receivables	9,299	31,088
Derivative Asset	32,261	52,107
Total financial assets	1,970,688	1,922,407
Long-term debt	7,075,179	5,140,059
Note payable to related party		30,493
Convertible debentures	433	623
Derivative financial instruments, liabilities	82,755	110,410
Total financial liabilities	7,173,578	5,297,150
Fair value \| Energy contracts \| Designated as a hedge \| Cash flow hedge
Fair Value of Financial Instruments [Line Items]
Derivative Asset	23,494	51,525
Derivative financial instruments, liabilities	15,384	5,597
Fair value \| Energy contracts \| Not designated as a hedge
Fair Value of Financial Instruments [Line Items]
Derivative Asset	279
Derivative financial instruments, liabilities	2,527
Fair value \| Energy contracts \| Not designated as a hedge \| Cash flow hedge
Fair Value of Financial Instruments [Line Items]
Derivative Asset		388
Derivative financial instruments, liabilities		332
Fair value \| Interest rate swaps \| Designated as a hedge
Fair Value of Financial Instruments [Line Items]
Derivative Asset	2,365
Derivative financial instruments, liabilities	9,124	19,649
Fair value \| Commodity contracts for regulatory operations
Fair Value of Financial Instruments [Line Items]
Derivative Asset	2,406	194
Derivative financial instruments, liabilities		614
Fair value \| Cross currency swap
Fair Value of Financial Instruments [Line Items]
Derivative Asset	3,717
Fair value \| Cross currency swap \| Designated as a hedge \| Net Investment Hedging
Fair Value of Financial Instruments [Line Items]
Derivative financial instruments, liabilities	55,720	84,218
Fair value \| Series C Preferred Stock
Fair Value of Financial Instruments [Line Items]
Preferred shares, Series C	$ 15,211	$ 15,565

Fair Value of Financial Instruments [Line Items]

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Long-term Investments, Fair Value

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Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

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Fair value portion of borrowing which can be exchanged for a specified number of another security at the option of the issuer or the holder, for example, but not limited to, the entity's common stock.

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Fair value, after the effects of master netting arrangements, of a financial asset or other contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes assets not subject to a master netting arrangement and not elected to be offset.

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Fair value, after the effects of master netting arrangements, of a financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset. Includes liabilities not subject to a master netting arrangement and not elected to be offset.

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Fair value of financial and nonfinancial obligations.

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The fair value amount of long-term debt whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission.

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Fair value portion of shares that an entity is required to redeem for cash or other assets at a fixed or determinable date or upon the occurrence of an event.

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The amount for notes payable (written promise to pay), due to related parties.

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Fair value portion of an agreement for an unconditional promise by the maker to pay the holder a definite sum of money at a future date.

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