Nature of Operations and Summary of Significant Policies - Narrative (Details) - USD ($) $ / shares in Units, $ in Thousands		1 Months Ended	3 Months Ended		6 Months Ended
	Apr. 30, 2020	Apr. 30, 2020	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2020	Mar. 31, 2019
Dividends Payable [Line Items]
Loans to customers under the program					$ 11,939	$ 383,665
Common stock dividends declared (in dollars per share)			$ 0.30	$ 0.25	$ 0.60	$ 0.50
Subsequent event
Dividends Payable [Line Items]
Loans to customers under the program		$ 600,000
Common stock dividends declared (in dollars per share)	$ 0.15