Earnings Per Share - Computation of Basic and Diluted Net Earnings Per Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ 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	$ 27,482	$ 28,589	$ 63,015	$ 39,152	$ 48,762	$ 47,282	$ 119,086	$ 135,196
Less: income allocable to participating securities				(18)				(62)
Income allocable to common shares	27,482			39,134			119,086	135,134
Add back: undistributed earnings allocable to participating securities				18				62
Less: undistributed earnings reallocated to participating securities				(18)				(61)
Numerator for diluted earnings per share	$ 27,482			$ 39,134			$ 119,086	$ 135,135
Denominator:
Basic weighted average shares outstanding	57,603			57,654			57,609	57,528
Dilutive effect of unvested restricted stock	568			729			703	875
Diluted weighted average shares outstanding	58,171			58,383			58,312	58,403
Earnings per share:
Earnings per share, basic	$ 0.48			$ 0.68			$ 2.07	$ 2.35
Earnings per share, diluted	$ 0.47			$ 0.67			$ 2.04	$ 2.31