Shareholders' Equity - Additional Information (Detail) - December 2019 Share Repurchase Program [Member] $ / shares in Units, shares in Millions	9 Months Ended
	Sep. 30, 2017 USD ($) $ / shares shares
Equity, Class of Treasury Stock [Line Items]
Share repurchase program, authorized amount	$ 100,000,000
Stock repurchase program, term (in years)	3 years
Stock repurchase program, expiring date	2019-12
Stock repurchased and retired, shares | shares	0.2
Stock repurchased and retired, value	$ 5,000,000
Stock repurchase program, average price in USD per share | $ / shares	$ 32.27
Stock repurchase program, remaining authorized repurchase amount	$ 94,000,000