Consolidated Balance Sheets (Parenthetical) - USD ($)	Mar. 31, 2019	Mar. 31, 2018
Statement Of Financial Position [Abstract]
Allowance for doubtful debts, accounts receivable	$ 5,508,000	$ 4,551,000
Common stock, par value	$ 0.0001	$ 0.0001
Common stock, shares authorized	120,000,000	120,000,000
Common stock, shares issued	54,021,032	53,793,986
Common stock, shares outstanding	18,557,794	18,912,907
Treasury stock, shares	35,463,238	34,881,079