Weighted Average Common Shares Basic and Common Shares Diluted (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Mar. 31, 2013	Dec. 30, 2012	Sep. 30, 2012	Jul. 01, 2012	Mar. 31, 2012	Jan. 01, 2012	Oct. 02, 2011	Jul. 03, 2011	Mar. 31, 2013	Mar. 31, 2012	Mar. 31, 2011
Earnings Per Share Disclosure [Line Items]
Net earnings attributable to EnerSys stockholders	$ 37,730	$ 39,184	$ 43,790	$ 45,804	$ 45,359	$ 36,859	$ 28,289	$ 33,496	$ 166,508	$ 144,003	$ 113,426
Basic									48,022,005	48,748,205	49,376,132
Common shares from exercise and lapse of equity awards, net of shares assumed reacquired									593,422	467,830	668,114
Convertible Notes	20,022								20,022
Diluted weighted-average number of common shares outstanding									48,635,449	49,216,035	50,044,246
Basic earnings per common share attributable to EnerSys stockholders	$ 0.79	$ 0.81	$ 0.91	$ 0.96	$ 0.95	$ 0.77	$ 0.57	$ 0.67	$ 3.47	$ 2.95	$ 2.30
Diluted earnings per common share attributable to EnerSys stockholders	$ 0.77	$ 0.80	$ 0.90	$ 0.95	$ 0.94	$ 0.77	$ 0.57	$ 0.66	$ 3.42	$ 2.93	$ 2.27
Anti-dilutive equity awards not included in diluted weighted-average common shares										221,097