Debt - Additional Information (Detail) - USD ($) $ in Thousands			1 Months Ended		3 Months Ended		9 Months Ended		12 Months Ended
	May 12, 2022	Apr. 20, 2018	Apr. 30, 2021	Oct. 31, 2017	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2022	Jun. 30, 2023	Feb. 01, 2023	Sep. 30, 2021	Apr. 14, 2021	Apr. 30, 2013
Debt Instrument [Line Items]
Borrowings outstanding under credit facility					$ 0		$ 0
Total debt					1,081,131		1,081,131		$ 1,264,522
Debt Instrument outstanding balance					1,081,131		1,081,131		1,264,522
Expenses associated with debt repayments and refinancing transactions					100	$ 783	326	$ 7,588
Non-Recourse Senior Secured Notes | Private Placement
Debt Instrument [Line Items]
Debt Instrument outstanding balance					146,800		146,800
Debt maturity date		Jan. 31, 2040
Stated interest rate		4.43%
Aggregate principal amount		$ 159,500
Scheduled maturity term		20 years
Expected project completion period		January 2020
Bank Credit Agreement | Term Loan A Due in May 2026
Debt Instrument [Line Items]
Current initial balance	$ 100,000
Term Loan A
Debt Instrument [Line Items]
Total debt					91,300		91,300
Senior Notes 4.625% Due 2023
Debt Instrument [Line Items]
Debt Instrument outstanding balance					0		0		$ 153,754		$ 153,800			$ 350,000
Stated interest rate									4.625%		4.625%			4.625%
Debt instrument redemption percentage of par									100.00%
Debt instrument repurchase amount									$ 196,200
Senior Notes 4.75% Due 2027
Debt Instrument [Line Items]
Debt Instrument outstanding balance				$ 250,000	$ 250,000		$ 250,000		250,000
Debt maturity date				Oct. 15, 2027			Oct. 31, 2027
Stated interest rate				4.75%	4.75%		4.75%
Debt instrument redemption percentage of par				100.00%
Senior Notes 8.25% Due 2026
Debt Instrument [Line Items]
Debt Instrument outstanding balance					$ 593,113		$ 593,113		$ 614,113
Debt maturity date			Apr. 15, 2026				Apr. 30, 2026
Stated interest rate			8.25%		8.25%		8.25%		8.25%				8.25%
Aggregate principal amount					$ 593,100		$ 593,100					$ 675,000
Expenses associated with debt repayments and refinancing transactions									$ 1,200
Debt instrument repurchase amount									$ 60,900
Senior Notes 8.25% Due 2026 | Redemption Beginning on April 15, 2024
Debt Instrument [Line Items]
Debt instrument redemption percentage of par							104.125%
Debt instrument redemption beginning period							Apr. 15, 2024
Senior Notes 8.25% Due 2026 | Redemption Beginning on April 15, 2025
Debt Instrument [Line Items]
Debt instrument redemption percentage of par							100.00%
Debt instrument redemption beginning period							Apr. 15, 2025
8.25% Senior Notes
Debt Instrument [Line Items]
Debt Instrument outstanding balance					$ 593,100		$ 593,100
Stated interest rate					8.25%		8.25%			8.25%
Expenses associated with debt repayments and refinancing transactions					$ 200
Debt instrument repurchase amount										$ 21,000
Bank Credit Facility [Member]
Debt Instrument [Line Items]
Bank credit facility aggregate principal amount	$ 350,000
Debt maturity period	May 31, 2026
Bank credit facility, aggregate principal amount of additional borrowing	$ 200,000
Bank credit facility, Consolidated EBITDA	50.00%
Percentage of capital stock of foreign subsidiary secured by pledge under Bank Credit Facility	65.00%
Percentage of loan to value	50.00%
Bank Credit Facility [Member] | Maximum
Debt Instrument [Line Items]
Total leverage ratio	4.5
Net unrestricted cash and cash equivalents related to total leverage ratio	$ 100,000
Secured leverage ratio	2.5
Net unrestricted cash and cash equivalents related to secured leverage ratio	$ 100,000
Fixed charge coverage ratio	1.75
Consolidated total leverage ratio	4
Bank Credit Facility [Member] | Base Rate
Debt Instrument [Line Items]
Debt instrument, percentage points added to reference rate							2.25%
Bank Credit Facility [Member] | Base Rate | Minimum
Debt Instrument [Line Items]
Debt instrument, percentage points added to reference rate	1.75%
Bank Credit Facility [Member] | Base Rate | Maximum
Debt Instrument [Line Items]
Debt instrument, percentage points added to reference rate	3.50%
Bank Credit Facility [Member] | Bloomberg Short-Term Bank Yield Index (BSBY)
Debt Instrument [Line Items]
Debt instrument, percentage points added to reference rate							3.25%
Bank Credit Facility [Member] | Bloomberg Short-Term Bank Yield Index (BSBY) | Minimum
Debt Instrument [Line Items]
Debt instrument, percentage points added to reference rate	2.75%
Bank Credit Facility [Member] | Bloomberg Short-Term Bank Yield Index (BSBY) | Maximum
Debt Instrument [Line Items]
Debt instrument, percentage points added to reference rate	4.50%
Revolving Credit Facility
Debt Instrument [Line Items]
Sublimit swing line loans	$ 25,000
Percentage of commitment fee to unfunded balance							0.45%
Line of credit facility, remaining borrowing capacity					232,600		$ 232,600
Sublimit for issuance of standby letters of credit	100,000
Revolving credit facility, Letters of credit outstanding					$ 17,400		$ 17,400
Revolving Credit Facility | Credit Agreement
Debt Instrument [Line Items]
Revolving credit facility, maximum borrowing capacity	$ 250,000