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Other - Narrative (Details) - USD ($)	3 Months Ended	9 Months Ended
Other - Narrative (Details) - USD ($)	Sep. 30, 2021	Sep. 30, 2021	Sep. 30, 2020	Sep. 15, 2021	Jun. 14, 2021	Dec. 31, 2020
Debt Instrument [Line Items]
Long-term Debt, Current Maturities	$ 450,000,000	$ 450,000,000				$ 526,412,000
Repayments of Long-term Debt		502,414,000	$ 450,000,000
Line of Credit Facility, Maximum Borrowing Capacity	800,000,000	800,000,000
Line of Credit Facility, Maximum Amount Outstanding During Period		33,000,000
Subsidiaries [Member]
Debt Instrument [Line Items]
Long-term Debt, Current Maturities	0	0				$ 2,412,000
Repayments of Long-term Debt		2,414,000	$ 0
Commercial Paper	0	0
2.379% Senior Secured Note Due 2028 [Member] \| Senior Secured Note
Debt Instrument [Line Items]
Long-term Debt, Gross					$ 500,000,000
Debt Instrument, Interest Rate, Stated Percentage					2.379%
Long-term Debt, Term					7 years
6.000% Senior Secured Note Due 2021 \| Senior Secured Note
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage					6.00%
Long-term Debt, Current Maturities					$ 500,000,000
$210M Term Loan Due 2022
Debt Instrument [Line Items]
Repayments of Long-term Debt	$ 210,000,000
Working Capital Needs [Member] \| Subsidiaries [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Amount Outstanding During Period		$ 0
2.893% Senior Secured Note Due 2051 \| Senior Secured Note \| Subsidiaries [Member]
Debt Instrument [Line Items]
Long-term Debt, Gross				$ 450,000,000
Debt Instrument, Interest Rate, Stated Percentage				2.893%
Long-term Debt, Term				30 years