Stockholders' Equity Repurchases of Common Shares (Narrative) (Detail) - USD ($)	12 Months Ended
	Mar. 31, 2018	Mar. 31, 2016
Stock repurchased and retired during period, value	$ (17,934,000)	$ (11,190,000)
Total Plan 2017
Stock repurchase program, authorized amount	25,000,000
Stock repurchase program, remaining authorized repurchase amount	$ 7,100,000