Shareholders' Equity - Additional Information (Detail)		1 Months Ended	3 Months Ended					12 Months Ended
	Oct. 30, 2017	Feb. 28, 2018 USD ($) shares	Dec. 31, 2018 USD ($) Vote $ / shares shares	Sep. 30, 2018 USD ($) $ / shares	Apr. 01, 2018 USD ($) shares	Dec. 31, 2017 $ / shares shares	Apr. 02, 2017 $ / shares	Dec. 31, 2018 USD ($) Vote $ / shares shares	Dec. 31, 2017 USD ($) $ / shares shares	Dec. 31, 2016 USD ($)	Apr. 25, 2018 shares	Feb. 01, 2018 USD ($)	Oct. 31, 2017 $ / shares	Apr. 12, 2017 USD ($)	Apr. 28, 2016 shares	Apr. 27, 2016 shares
Class of Stock [Line Items]
Authorized shares | shares			400,000					400,000
Preferred stock par value (in dollars per share) | $ / shares			$ 0.01					$ 0.01
Common stock, shares authorized | shares			300,000,000			200,000,000		300,000,000	200,000,000		300,000,000				10,000,000	200,000,000
Stock split	2					2			2
Common stock par value, in dollars per share | $ / shares			$ 0.002			$ 0.002		$ 0.002	$ 0.002				$ 0.002
Vote entitled for each common share outstanding | Vote			1					1
Repurchase of common stock								$ 203,822,000	$ 123,715,000	$ 47,149,000
Cash dividend declared per common share | $ / shares			$ 0.0500	$ 0.0425		$ 0.0450	$ 0.0375
Payments of dividends								31,865,000	$ 29,037,000
Repurchase Program 2014 [Member]
Class of Stock [Line Items]
total shares repurchased | shares					1,744,000
Repurchase of common stock, shares | shares					803,000
Repurchase of common stock					$ 45,200,000
Repurchase Program 2015 [Member]
Class of Stock [Line Items]
Repurchase of authorized common stock			$ 191,378,000					$ 191,378,000						$ 100,000,000
Repurchase of common stock, shares | shares		3,174,000						203,000
Repurchase of common stock		$ 150,000,000						$ 8,622,000
Repurchase Program November 2015 [Member]
Class of Stock [Line Items]
Repurchase of authorized common stock				$ 200,000,000								$ 150,000,000
Common Stock [Member] | Repurchase Program 2014 [Member]
Class of Stock [Line Items]
Repurchased shares, total cost					$ 100,000,000