Goodwill - Carrying Amount of Goodwill (Details) - USD ($)	3 Months Ended		6 Months Ended		12 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2020	Mar. 31, 2019	Sep. 30, 2019
Goodwill [Roll Forward]
Balance, beginning of period			$ 739,023,000	$ 739,023,000	$ 739,023,000
Goodwill acquired during the period			1,539,000		0
Goodwill impairment during the period	$ (740,600,000)	$ 0	(740,562,000)	$ 0	0
Balance, end of period	$ 0		$ 0		$ 739,023,000