Additional Paid in Capital and Insurance Subsidiaries Activity in Stockholders' Equity (Details) (USD $)	3 Months Ended	12 Months Ended
	Jun. 30, 2011	Mar. 31, 2013	Mar. 31, 2012	Mar. 31, 2011
Additional paid in capital:
Payments for repurchase preferred stock		$ 0	$ 144,289,000	$ 0
Series A preferred stock redemption date	Jun. 01, 2011
Insurance subsidiaries
Additional paid in capital:
Payments for repurchase preferred stock			7,700,000
Reduction of insurance company holdings			5,900,000
Amerco, Business Segment [Member]
Additional paid in capital:
Prior to redemption additional paid-in capital cost			146,300,000
Payments for repurchase preferred stock			151,997,000
Series A preferred stock redemption date			Jun. 01, 2011
Payments for repurchase of preferred stock and preference stock			$ 152,500,000