CONSOLIDATED STATEMENT OF COMPREHENSIVE INCOME (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Mar. 31, 2011
Income Statement [Abstract]
Sales	$ 4,362,145	$ 4,613,399	$ 4,842,264
Cost of sales	3,421,276	3,618,503	3,840,698
Gross profit	940,869	994,896	1,001,566
Operating expenses:
Research and development	64,678	66,403	64,960
Selling	162,359	169,984	164,063
General and administrative	244,189	262,923	246,817
Income before interest, loss on extinguishment of debt, income taxes, and noncontrolling interest	469,643	495,586	525,726
Interest expense	(65,924)	(89,296)	(87,612)
Interest income	538	676	560
Loss on extinguishment of debt	(11,773)	0	0
Income before income taxes and noncontrolling interest	392,484	406,966	438,674
Income tax provision	120,243	143,762	124,963
Net income	272,241	263,204	313,711
Less net income attributable to noncontrolling interest	436	592	536
Net income attributable to Alliant Techsystems Inc.	271,805	262,612	313,175
Alliant Techsystems Inc. earnings per common share:
Basic (in dollars per share)	$ 8.38	$ 7.99	$ 9.41
Diluted (in dollars per share)	$ 8.34	$ 7.93	$ 9.32
Cash dividends paid per share (in dollars per share)	$ 0.92	$ 0.8	$ 0.2
Alliant Techsystems Inc. weighted-average number of common shares outstanding:
Basic (in shares)	32,447	32,874	33,275
Diluted (in shares)	32,608	33,112	33,615
Other comprehensive income (loss), net of tax:
Net Income (from above)	272,241	263,204	313,711
Pension and other postretirement benefit liabilities:
Reclassification of prior service credits for pension and postretirement benefit plans recorded to net income, net of tax benefit of $3,366, $3,370, and $3,600	(5,406)	(5,392)	(5,785)
Reclassification of net actuarial loss for pension and postretirement benefit plans recorded to net income, net of tax expense of $(49,192), $(38,042), and $(33,962)	78,062	60,864	54,569
Valuation adjustment for pension and postretirement benefit plans, net of tax (expense) benefit of $(9,575), $94,968, and $4,009	15,456	(152,066)	(4,844)
Change in fair value of derivatives, net of tax expense of $3,586, $17,060, and $6,078, respectively	(5,608)	(26,683)	(9,607)
Change in fair value of available-for-sale securities, net of tax benefit of $135, $156, and $205, respectively	(210)	(244)	(324)
Total other comprehensive income (loss)	82,294	(123,521)	34,009
Comprehensive income	354,535	139,683	347,720
Less comprehensive income attributable to noncontrolling interest	436	592	536
Comprehensive income attributable to Alliant Techsystems Inc.	$ 354,099	$ 139,091	$ 347,184