Earnings per Share (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2020	Sep. 30, 2019
Numerator:
Net income	$ 5,947	$ 8,714	$ 486	$ 100,423	$ 11,526	$ (612)	$ 15,147	$ 111,337
Denominator:
Weighted average shares outstanding, basic (in shares)	54,666,128			53,297,298			54,325,832	53,052,521
Effect of dilutive securities (in shares)	542,904			1,244,327			728,940	1,751,330
Weighted average shares outstanding, diluted (in shares)	55,209,032			54,541,625			55,054,772	54,803,851
Net income per share, basic and diluted:
Basic (in dollars per share)	$ 0.11			$ 1.88			$ 0.28	$ 2.10
Diluted (in dollars per share)	$ 0.11			$ 1.84			$ 0.28	$ 2.03
Antidilutive securities excluded from calculations of diluted net income per share (in shares)	3,898,896			2,646,933			3,602,648	1,826,279