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v3.20.4

Long-term Debt (Details) $ in Thousands | 12 Months Ended |  |
--- | --- | --- | ---
Dec. 31, 2020 USD ($) | Sep. 30, 2020 USD ($) | Dec. 31, 2019 USD ($)
Line of Credit Facility [Line Items] |  |  |
Line of credit facility |  | $ 500,000 |
Maximum borrowing capacity | $ 550,000 |  |
Percentage of subsidiary stock securing debt (in hundredths) | 0.65 |  |
Unused commitment fee on the average daily unused portion (in hundredths) | 0.25% |  |
Average interest rate for the year | 2.40% |  |
Letters of Credit Outstanding, Amount | $ 1,000 |  |
Long-term debt | $ 369,400 |  | $ 269,400
Long-term Debt, Maturity Date | Sep. 13, 2024 |  |
Alternate base rates, applicable margins [Abstract] |  |  |
Applicable margin, federal funds rate (in hundredths) | 0.50% |  |
Applicable margin, 30-day LIBOR (in hundredths) | 2.00% |  |
LIBOR Borrowings [Member] |  |  |
Line of Credit Facility [Line Items] |  |  |
Description of basis for variable rate | LIBOR |  |
Minimum [Member] | LIBOR Borrowings [Member] | London Interbank Offered Rate (LIBOR) [Member] |  |  |
Line of Credit Facility [Line Items] |  |  |
Debt Instrument, Basis Spread on Variable Rate | 1.50% |  |
Minimum [Member] | Alternate Base Rate Borrowings [Member] | Base Rate [Member] |  |  |
Line of Credit Facility [Line Items] |  |  |
Debt Instrument, Basis Spread on Variable Rate | 0.00% |  |
Maximum [Member] | LIBOR Borrowings [Member] | London Interbank Offered Rate (LIBOR) [Member] |  |  |
Line of Credit Facility [Line Items] |  |  |
Debt Instrument, Basis Spread on Variable Rate | 2.25% |  |
Maximum [Member] | Alternate Base Rate Borrowings [Member] | Base Rate [Member] |  |  |
Line of Credit Facility [Line Items] |  |  |
Debt Instrument, Basis Spread on Variable Rate | 0.50% |  |

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