Preferred and Common Stockholder's Equity - Schedule of Stock Repurchases (Detail) - USD ($) shares in Millions, $ in Millions	9 Months Ended	12 Months Ended
	Mar. 31, 2019	Jun. 30, 2019
Stockholders Equity [Line Items]
Shares purchased and retired		1.6
Common stock and additional paid-in-capital reductions	$ 16.9
Charges to retained earnings	$ 33.1
Common Stock [Member]
Stockholders Equity [Line Items]
Shares purchased and retired	1.6