Consolidated Balance Sheets (Parenthetical) - USD ($)	Mar. 31, 2018	Mar. 31, 2017
Statement Of Financial Position [Abstract]
Allowance for doubtful debts, accounts receivable	$ 4,551,000	$ 3,001,000
Common stock, par value	$ 0.0001	$ 0.0001
Common stock, shares authorized	120,000,000	120,000,000
Common stock, shares issued	53,793,986	53,569,067
Common stock, shares outstanding	18,912,907	18,937,233
Treasury stock, shares	34,881,079	34,631,834