Stockholders' Equity (Detail)		3 Months Ended
	May 15, 2019 USD ($) sales_agent	Sep. 30, 2019 USD ($) $ / shares shares
Class of Stock [Line Items]
Number of sales agents | sales_agent	9
At the Market Equity Distribution Agreement
Class of Stock [Line Items]
Aggregate offering price of common shares	$ 500,000,000
Shares issued (in shares) | shares		849,200
Average sales price (in dollars per share) | $ / shares		$ 119.30
Net proceeds		$ 100,056,000
Value of stock available for issuance under ATM		$ 298,621,000