Shareholders' Equity - Additional Information (Detail) - USD ($)		3 Months Ended	6 Months Ended
	Sep. 30, 2017	Sep. 30, 2017	Sep. 30, 2017	Dec. 31, 2016
Equity Class Of Treasury Stock [Line Items]
Options outstanding	0	0	0
Warrants outstanding	0	0	0
Other potentially dilutive securities outstanding	0	0	0
Common Stock
Equity Class Of Treasury Stock [Line Items]
Stock repurchase program, authorized amount	$ 10,000,000	$ 10,000,000	$ 10,000,000
Stock repurchase program, additional authorized repurchase amount	$ 5,000,000	$ 5,000,000	$ 5,000,000
Stock repurchase program, expiration date			Jun. 30, 2018
Number of common shares repurchased	2,557,031	2,473,918
Common Stock | Maximum
Equity Class Of Treasury Stock [Line Items]
Stock repurchase program, authorized amount				$ 5,000,000