Stockholders' Equity - Additional Information (Detail) - USD ($)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018	Aug. 02, 2018	Nov. 17, 2016
Class Of Stock [Line Items]
Capitalized stock-based compensation costs	$ 0	$ 0	$ 0	$ 0
Stock options granted	0	0	0	0
Share issued, exercise of options and release of stock awards			1,500,000		1,600,000
Shares settled for tax withholding			658,000	629,000
Common stock repurchased, amount			$ 102,160,000	$ 101,905,000
Repurchase of unsettled common stock			$ 9,301,000	$ 0
November 2016 Stock Repurchase Program [Member]
Class Of Stock [Line Items]
Stock repurchase program, authorized amount							$ 200,000,000
Common stock repurchased, shares		0		7,700,000
Common stock repurchased, amount				$ 101,900,000
August 2018 Stock Repurchase Program [Member]
Class Of Stock [Line Items]
Stock repurchase program, authorized amount						$ 250,000,000
Common stock repurchased, shares	3,500,000		9,600,000
Common stock repurchased, amount	$ 37,100,000		$ 102,200,000
Stock repurchase program, shares yet to be purchased	$ 111,100,000		$ 111,100,000
Repurchase of unsettled common stock, shares	900,000
Repurchase of unsettled common stock	$ 9,300,000
Transaction settlement date			2019-10