Fair Value Measurements - Narrative (Details) - USD ($)	Dec. 31, 2021	Sep. 30, 2021
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Estimated fair value	$ 1,547,500,000	$ 1,620,300,000
Face value	889,400,000	918,000,000
Revolving Credit Facility
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Balance outstanding	$ 0	$ 0