Shareholders' Equity - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2017
Stockholders Equity Note [Abstract]
Share repurchase program, authorized amount			$ 75,000,000
Common stock repurchased, shares	1,544,681
Common stock repurchased, amount	$ 63,425,000	$ 11,575,000
Common stock repurchased, price per share	$ 41.06