Share-Based Employee Compensation - Stock Option Activities (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Number of Shares
Number of Shares, Options outstanding, beginning balance	635,000
Number of Shares, Granted	0	0	0
Number of shares, Exercised	(37,000)
Number of Shares, Forfeited	0
Number of Shares, Expired	0
Number of Shares, Options outstanding, ending balance	598,000	635,000
Number of Shares, Vested and expected to vest at end of period	598,000
Number of Shares, Options exercisable at end of period	598,000
Weighted-Average Exercise Price Per Share
Weighted Average Exercise Price, Options outstanding, beginning balance (in dollars per share)	$ 6.53
Weighted Average Exercise Price, Granted (in dollars per share)	0
Weighted Average Exercise Price, Exercised (in dollars per share)	6.71
Weighted Average Exercise Price, Forfeited (in dollars per share)	0
Weighted Average Exercise Price, Expired (in dollars per share)	0
Weighted Average Exercise Price, Options outstanding, ending balance (in dollars per share)	6.52	$ 6.53
Weighted Average Exercise Price, Vested and expected to vest at end of period (in dollars per share)	6.52
Weighted Average Exercise Price, Options exercisable at end of period (in dollars per share)	$ 6.52
Weighted-Average Remaining Contractual Term
Weighted Average Remaining Life, Options outstanding at end of period	2 years 1 month 2 days
Weighted Average Remaining Life, Vested and expected to vest at end of period	2 years 1 month 2 days
Weighted Average Remaining Life, Options exercisable at end of period	2 years 1 month 2 days
Aggregate Intrinsic Value
Outstanding aggregate intrinsic value	$ 10,457
Vested and expected to vest in the future, aggregate intrinsic value	10,457
Exercisable, aggregate intrinsic value	$ 10,457