Change in Number of Shares of Common Stock Outstanding (Detail) - shares		12 Months Ended
	Jul. 17, 2015	Mar. 31, 2018	Mar. 31, 2017	Mar. 31, 2016
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shares outstanding, beginning balance		43,447,536	43,189,502	44,068,588
Purchase of treasury stock		(1,756,831)	(1,756,831)	(3,216,654)
Shares issued from treasury stock to settle conversion premium on Convertible Notes	1,889,431		1,889,431	1,889,431
Shares issued as part of equity-based compensation plans, net of equity awards surrendered for option price and taxes		224,295	258,034	448,137
Shares outstanding, ending balance		41,915,000	43,447,536	43,189,502