Shareholders' Equity - Additional Information (Detail) - USD ($)	12 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Sep. 30, 2017	Dec. 31, 2016
Equity Class Of Treasury Stock [Line Items]
Common shares, shares authorized	75,000,000	75,000,000
Common shares, par value	$ 0.01	$ 0.01
Common shares, shares outstanding	22,799,088	27,065,852
Treasury stock, shares	30,166,709	25,899,945
Cost of shares repurchased under common stock repurchase program	$ 6,293,000	$ 66,000
Cost of shares repurchased under common stock repurchase program	$ 30,583,000	$ 24,290,000
Preferred shares, shares issued	3,677	3,677
Preferred shares, shares outstanding	3,677	3,677
Preferred shares, par value	$ 0.01
Preferred shares, liquidation preference	$ 3,677,000	$ 3,677,000
Common Stock
Equity Class Of Treasury Stock [Line Items]
Stock repurchase program, authorized amount			$ 10,000,000
Stock repurchase program, additional authorized repurchase amount			$ 5,000,000
Stock repurchase program, expiration date	Dec. 31, 2018
Number of common shares repurchased	4,266,764
Cost of shares repurchased under common stock repurchase program	$ 6,292,620
Stock repurchase program, remaining balance	$ 3,640,762
Common Stock | Common Stock Repurchase Program
Equity Class Of Treasury Stock [Line Items]
Treasury stock, shares	4,330,744
Cost of shares repurchased under common stock repurchase program	$ 6,359,238
Common Stock | Maximum
Equity Class Of Treasury Stock [Line Items]
Stock repurchase program, authorized amount				$ 5,000,000