Subsequent Events - Additional Information (Detail) - Subsequent Event [Member]	Oct. 23, 2017 $ / shares
Dividend Declared [Member]
Subsequent Event [Line Items]
Cash dividend per share	$ 0.20
Date of payment to shareholders entitled to dividends	Dec. 28, 2017
Date of record of shareholders entitled to dividends	Dec. 14, 2017
Extraordinary Dividend Declared [Member]
Subsequent Event [Line Items]
Cash dividend per share	$ 3.50
Date of payment to shareholders entitled to dividends	Dec. 28, 2017
Date of record of shareholders entitled to dividends	Dec. 14, 2017