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Summary of Significant Accounting Policies - Shares Used in Computing Basic and Diluted Earnings Per Share (Details) - shares		1 Months Ended	3 Months Ended		6 Months Ended
	Aug. 21, 2019	Aug. 31, 2019	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2020	Mar. 31, 2019
Denominator:
Weighted-average common shares outstanding - basic (in shares)			208,941,000	174,501,000	209,151,000	174,461,000
Incremental shares issuable for stock options and awards (in shares)			867,000	2,817,000	1,343,000	2,985,000
Weighted-average common shares outstanding - diluted (in shares)			209,808,000	177,318,000	210,494,000	177,446,000
Business Acquisition [Line Items]
Antidilutive shares excluded from calculation of earnings per share (in shares)			8,020,000	208,000	8,020,000	208,000
Merger Sub \| Common Stock
Business Acquisition [Line Items]
Shares issued in business acquisition (in shares)	34,612,847	34,613,000