Stockholders' Equity - Additional Information (Detail) - USD ($)		3 Months Ended		9 Months Ended
	Aug. 16, 2018	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Aug. 13, 2018	Dec. 01, 2017	May 18, 2017	Jun. 02, 2016
Stockholders Equity [Line Items]
Value of shares retired				$ 29,220,000
2016 Stock Repurchase Program
Stockholders Equity [Line Items]
Stock repurchase program authorized amount							$ 300,000,000		$ 100,000,000
Stock repurchase program additional amount authorized							$ 100,000,000.0	$ 100,000,000
Available amount under repurchase program		$ 99,100,000		$ 99,100,000
Shares of common stock repurchased and retired (in shares)		0	1,599,000	0	4,366,000
Average price paid per share (in dollars per share)		$ 0.00	$ 32.98	$ 42.17	$ 35.55
Value of shares retired		$ 0	$ 52,741,000	$ 14,213,000	$ 155,198,000
August 2023 Convertible Note Conversion Program
Stockholders Equity [Line Items]
Stock repurchase program authorized amount						$ 25,000,000.0
Shares of common stock repurchased and retired (in shares)	196,050
Average price paid per share (in dollars per share)	$ 76.51
Value of shares retired	$ 15,000,000