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Long-Term Debt (Narrative) (Details) |  | 6 Months Ended |
--- | --- | --- | ---
Jan. 24, 2019 USD ($) | Jun. 30, 2022 USD ($) debtCovenant | Dec. 31, 2021 USD ($)
Debt Instrument [Line Items] |  |  |
Revolving credit facility, leverage ratio, multiplier, minimum | 3.0 |  |
Revolving Credit Facility | Senior Credit Agreement |  |  |
Debt Instrument [Line Items] |  |  |
Revolving credit facility, availability amount |  | $ 301,500,000 | $ 369,300,000
Line of Credit | Revolving credit facility |  |  |
Debt Instrument [Line Items] |  |  |
Current borrowing capacity | $ 400,000,000 |  |
Letters of credit issued | 700,000,000 |  |
Number of debt covenants | debtCovenant |  | 3 |
Revolving credit facility, annual borrowing capacity, maximum | $ 75,000,000 |  |
Line of Credit | Revolving credit facility | Minimum |  |  |
Debt Instrument [Line Items] |  |  |
Revolving credit facility, undrawn commitment fee | 0.15% |  |
Line of Credit | Revolving credit facility | Minimum | London Interbank Offered Rate (LIBOR) |  |  |
Debt Instrument [Line Items] |  |  |
Revolving credit facility, interest rates margin | 1.125% |  |
Line of Credit | Revolving credit facility | Maximum |  |  |
Debt Instrument [Line Items] |  |  |
Revolving credit facility, undrawn commitment fee | 0.25% |  |
Line of Credit | Revolving credit facility | Maximum | London Interbank Offered Rate (LIBOR) |  |  |
Debt Instrument [Line Items] |  |  |
Revolving credit facility, interest rates margin | 2.00% |  |
Line of Credit | Standby Letters of Credit | Senior Credit Agreement |  |  |
Debt Instrument [Line Items] |  |  |
Debt instrument, issued value |  | $ 4,500,000 |
Medium-term Notes | Revolving credit facility |  |  |
Debt Instrument [Line Items] |  |  |
Debt instrument, issued value | $ 300,000,000 |  |

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