Summary of Significant Accounting Policies - Shares Used in Computing Basic and Diluted Earnings Per Share (Details) - shares	3 Months Ended		9 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Denominator:
Weighted-average common shares outstanding - basic (in shares)	209,099,000	208,598,000	208,934,000	208,989,000
Incremental shares issuable for stock options and awards (in shares)	1,752,000	377,000	1,260,000	1,020,000
Weighted-average common shares outstanding - diluted (in shares)	210,851,000	208,975,000	210,194,000	210,009,000
Antidilutive securities excluded from computation of earnings per share (in shares)	2,502	2,502	7,083	7,083