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Short-Term and Long-Term Borrowings - Narrative (Details) - USD ($)	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Oct. 31, 2022	Jun. 10, 2021
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity	$ 340,000,000
Debt, weighted average interest rate (as a percent)	5.61%	1.42%
Senior Notes
Debt Instrument [Line Items]
Aggregate principal amount				$ 230,000,000
Proceeds from issuance of debt	$ 90,000,000	$ 140,000,000
Minimum
Debt Instrument [Line Items]
Interest and dividend coverage ratio	1.50
Minimum | Benchmark rate
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate	0.00%
Maximum
Debt Instrument [Line Items]
Debt to total capitalization ratio	60.00%
Maximum | Benchmark rate
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate	2.00%
OTC Credit Agreement
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity	$ 170,000,000
Line of credit facility, increased current borrowing capacity, accordion provision			$ 290,000,000
OTP Credit Agreement
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity	$ 170,000,000
Line of credit facility, increased current borrowing capacity, accordion provision			250,000,000
Series 2021A Senior Unsecured Notes
Debt Instrument [Line Items]
Rate (as a percent)	2.74%
Series 2021A Senior Unsecured Notes | Senior Notes
Debt Instrument [Line Items]
Aggregate principal amount				$ 40,000,000
Rate (as a percent)				2.74%
Series 2021B Senior Unsecured Notes
Debt Instrument [Line Items]
Rate (as a percent)	3.69%
Series 2021B Senior Unsecured Notes | Senior Notes
Debt Instrument [Line Items]
Aggregate principal amount				$ 100,000,000
Rate (as a percent)				3.69%
Series 2022A Senior Unsecured Notes
Debt Instrument [Line Items]
Rate (as a percent)	3.77%
Series 2022A Senior Unsecured Notes | Senior Notes
Debt Instrument [Line Items]
Aggregate principal amount				$ 90,000,000
Rate (as a percent)				3.77%
Revolving Credit Facility | OTC Credit Agreement
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity			170,000,000
Revolving Credit Facility | OTP Credit Agreement
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity			170,000,000
Letter of Credit | OTC Credit Agreement
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity			40,000,000
Letter of Credit | OTP Credit Agreement
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity			$ 50,000,000

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Line of Credit Facility, Increased Current Borrowing Capacity, Accordion Provision

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Face (par) amount of debt instrument at time of issuance.

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Contractual interest rate for funds borrowed, under the debt agreement.

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Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

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The cash inflow from a borrowing with the highest claim on the assets of the entity in case of bankruptcy or liquidation (with maturities initially due after one year or beyond the operating cycle, if longer).

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