Stockholders' Equity - Additional Information (Detail) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Jul. 09, 2018
Equity Class Of Treasury Stock [Line Items]
Stock-based compensation expense	$ 2,100,000	$ 1,900,000	$ 11,100,000	$ 10,900,000
Additional common shares issued under deferred and stock compensation arrangements			435,772
Purchases, shares			2,373,554
Long Term Incentive Plan
Equity Class Of Treasury Stock [Line Items]
Purchases, shares			12,708
Common Stock Repurchase Plan
Equity Class Of Treasury Stock [Line Items]
Purchases, shares			2,360,846
Stock repurchase program, remaining authorized amount					$ 241,000,000
Stock repurchase program, authorized amount					$ 300,000,000