Consolidated Balance Sheet by Industry Segment (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013		Mar. 31, 2012		Mar. 31, 2011		Mar. 31, 2010
ASSETS:
Cash and cash equivalents	$ 463,744		$ 357,180		$ 382,514		$ 244,118
Reinsurance recoverables and trade receivables, net	261,789		297,974
Inventories, net	56,396		58,735
Prepaid expenses	57,451		41,858
Investments, fixed maturities and marketable equities	1,095,338		766,792
Investments, other	241,765		258,551
Deferred policy acquisition costs, net	93,043		63,914
Other assets	99,986		120,525
Related party assets	182,035		316,157
Subtotal assets	2,551,547		2,281,686
Property, plant and equipment, at cost:
Land	333,228		281,140
Buildings and improvements	1,197,875		1,087,119
Furniture and equipment	311,142		308,120
Property, plant and equipment (gross)	4,314,409		3,787,822
Less: Accumulated depreciation	(1,559,355)		(1,415,457)
Total property, plant and equipment	2,755,054		2,372,365
Total assets	5,306,601		4,654,051		4,191,433
Liabilities:
Accounts payable and accrued expenses	358,491		335,326
Notes, loans and leases payable	1,661,845		1,486,211
Policy benefits and losses, claims and loss expenses payable	1,115,048		1,145,943
Liabilities from investment contracts	510,789		240,961
Other policyholders' funds and liabilities	7,294		7,273
Deferred income	30,217		31,525
Deferred income taxes	393,658		370,992
Total liabilities	4,077,342		3,618,231
Stockholders' equity:
Additional paid-in capital	438,168		433,743
Accumulated other comprehensive loss	(22,680)		(45,436)
Retained earnings	1,482,630		1,317,064
Unearned employee stock ownership plan shares	(1,706)		(2,398)
Total stockholders' equity	1,229,259		1,035,820
Total liabilities and stockholders' equity	5,306,601		4,654,051
Rental trailers and other rental equipment
Property, plant and equipment, at cost:
Property subject to or available for operating lease, gross	317,476		255,010
Rental trucks
Property, plant and equipment, at cost:
Property subject to or available for operating lease, gross	2,154,688		1,856,433
Series A preferred stock
Stockholders' equity:
Preferred stock, value, issued
Series B preferred stock
Stockholders' equity:
Preferred stock, value, issued
Series A common stock
Stockholders' equity:
Common stock, value, issued
Common stock
Stockholders' equity:
Common stock, value, issued	10,497		10,497
Cost of common shares in treasury, net
Stockholders' equity:
Treasury stock, value	(525,653)		(525,653)
Cost of preferred shares in treasury, net
Stockholders' equity:
Treasury stock, value	(151,997)		(151,997)
Property and Casualty Insurance
ASSETS:
Cash and cash equivalents	14,120	[1]	22,542	[2]	21,718	[3]	22,126	[4]
Reinsurance recoverables and trade receivables, net	186,010	[1]	231,211	[2]
Inventories, net	0		0
Prepaid expenses	0	[1]	0	[2]
Investments, fixed maturities and marketable equities	160,455	[1]	132,270	[2]
Investments, other	65,212	[1]	74,757	[2]
Deferred policy acquisition costs, net	0	[1]	0	[2]
Other assets	1,212	[1]	1,507	[2]
Related party assets	8,846	[1]	7,542	[2]
Subtotal assets	435,855	[1]	469,829	[2]
Investments in subsidiaries	0	[1]	0	[2]
Property, plant and equipment, at cost:
Land	0	[1]	0	[2]
Buildings and improvements	0	[1]	0	[2]
Furniture and equipment	0	[1]	0	[2]
Property, plant and equipment (gross)	0	[1]	0	[2]
Less: Accumulated depreciation	0	[1]	0	[2]
Total property, plant and equipment	0	[1]	0	[2]
Total assets	435,855	[1]	469,829	[2]
Liabilities:
Accounts payable and accrued expenses	0	[1]	0	[2]
Notes, loans and leases payable	0	[1]	0	[2]
Policy benefits and losses, claims and loss expenses payable	330,184	[1]	382,939	[2]
Liabilities from investment contracts	0	[1]	0	[2]
Other policyholders' funds and liabilities	3,157	[1]	3,438	[2]
Deferred income	0	[1]	0	[2]
Deferred income taxes	(36,241)	[1]	(41,945)
Related party liabilities	1,844	[1]	1,555	[2]
Total liabilities	298,944	[1]	345,987	[2]
Stockholders' equity:
Additional paid-in capital	91,120	[1]	89,620	[2]
Accumulated other comprehensive loss	4,568	[1]	2,255	[2]
Retained earnings	37,922	[1]	28,666	[2]
Unearned employee stock ownership plan shares	0	[1]	0	[2]
Total stockholders' equity	136,911	[1]	123,842	[2]
Total liabilities and stockholders' equity	435,855	[1]	469,829	[2]
Property and Casualty Insurance | Rental trailers and other rental equipment
Property, plant and equipment, at cost:
Property subject to or available for operating lease, gross	0	[1]	0	[2]
Property and Casualty Insurance | Rental trucks
Property, plant and equipment, at cost:
Property subject to or available for operating lease, gross	0	[1]	0	[2]
Property and Casualty Insurance | Series A preferred stock
Stockholders' equity:
Preferred stock, value, issued	0	[1]	0	[2]
Property and Casualty Insurance | Series B preferred stock
Stockholders' equity:
Preferred stock, value, issued	0	[1]	0	[2]
Property and Casualty Insurance | Series A common stock
Stockholders' equity:
Common stock, value, issued	0	[1]	0	[2]
Property and Casualty Insurance | Common stock
Stockholders' equity:
Common stock, value, issued	3,301	[1]	3,301	[2]
Property and Casualty Insurance | Cost of common shares in treasury, net
Stockholders' equity:
Treasury stock, value	0	[1]	0	[2]
Property and Casualty Insurance | Cost of preferred shares in treasury, net
Stockholders' equity:
Treasury stock, value	0	[1]	0	[2]
Life Insurance
ASSETS:
Cash and cash equivalents	22,064	[1]	25,410	[2]	37,301	[3]	14,287	[4]
Reinsurance recoverables and trade receivables, net	32,520	[1]	29,660	[2]
Inventories, net	0		0
Prepaid expenses	0	[1]	0	[2]
Investments, fixed maturities and marketable equities	913,655	[1]	617,494	[2]
Investments, other	125,900	[1]	131,461	[2]
Deferred policy acquisition costs, net	93,043	[1]	63,914	[2]
Other assets	157	[1]	203	[2]
Related party assets	514	[1]	482	[2]
Subtotal assets	1,187,853	[1]	868,624	[2]
Investments in subsidiaries	0	[1]	0	[2]
Property, plant and equipment, at cost:
Land	0	[1]	0	[2]
Buildings and improvements	0	[1]	0	[2]
Furniture and equipment	0	[1]	0	[2]
Property, plant and equipment (gross)	0	[1]	0	[2]
Less: Accumulated depreciation	0	[1]	0	[2]
Total property, plant and equipment	0	[1]	0	[2]
Total assets	1,187,853	[1]	868,624	[2]
Liabilities:
Accounts payable and accrued expenses	8,139	[1]	10,060	[2]
Notes, loans and leases payable	0	[1]	0	[2]
Policy benefits and losses, claims and loss expenses payable	404,040	[1]	382,864	[2]
Liabilities from investment contracts	510,789	[1]	240,961	[2]
Other policyholders' funds and liabilities	4,137	[1]	3,835	[2]
Deferred income	0	[1]	0	[2]
Deferred income taxes	17,810	[1]	14,945
Related party liabilities	208	[1]	172	[2]
Total liabilities	945,123	[1]	652,837	[2]
Stockholders' equity:
Additional paid-in capital	26,271	[1]	26,271	[2]
Accumulated other comprehensive loss	37,567	[1]	23,888	[2]
Retained earnings	176,392	[1]	163,128	[2]
Unearned employee stock ownership plan shares	0	[1]	0	[2]
Total stockholders' equity	242,730	[1]	215,787	[2]
Total liabilities and stockholders' equity	1,187,853	[1]	868,624	[2]
Life Insurance | Rental trailers and other rental equipment
Property, plant and equipment, at cost:
Property subject to or available for operating lease, gross	0	[1]	0	[2]
Life Insurance | Rental trucks
Property, plant and equipment, at cost:
Property subject to or available for operating lease, gross	0	[1]	0	[2]
Life Insurance | Series A preferred stock
Stockholders' equity:
Preferred stock, value, issued	0	[1]	0	[2]
Life Insurance | Series B preferred stock
Stockholders' equity:
Preferred stock, value, issued	0	[1]	0	[2]
Life Insurance | Series A common stock
Stockholders' equity:
Common stock, value, issued	0	[1]	0	[2]
Life Insurance | Common stock
Stockholders' equity:
Common stock, value, issued	2,500	[1]	2,500	[2]
Life Insurance | Cost of common shares in treasury, net
Stockholders' equity:
Treasury stock, value	0	[1]	0	[2]
Life Insurance | Cost of preferred shares in treasury, net
Stockholders' equity:
Treasury stock, value	0	[1]	0	[2]
Eliminations
ASSETS:
Cash and cash equivalents	0		0		0		0
Reinsurance recoverables and trade receivables, net	0		0
Inventories, net	0		0
Prepaid expenses	0		0
Investments, fixed maturities and marketable equities	0		0
Investments, other	0		0
Deferred policy acquisition costs, net	0		0
Other assets	0		0
Related party assets	(11,526)	[5]	(10,057)	[5]
Subtotal assets	(11,526)		(10,057)
Investments in subsidiaries	(379,641)	[6]	(339,629)	[6]
Property, plant and equipment, at cost:
Land	0		0
Buildings and improvements	0		0
Furniture and equipment	0		0
Property, plant and equipment (gross)	0		0
Less: Accumulated depreciation	0		0
Total property, plant and equipment	0		0
Total assets	(391,167)		(349,686)
Liabilities:
Accounts payable and accrued expenses	0		0
Notes, loans and leases payable	0		0
Policy benefits and losses, claims and loss expenses payable	0		0
Liabilities from investment contracts	0		0
Other policyholders' funds and liabilities	0		0
Deferred income	0		0
Deferred income taxes	0		0
Related party liabilities	(11,526)	[5]	(10,057)	[5]
Total liabilities	(11,526)		(10,057)
Stockholders' equity:
Additional paid-in capital	(117,601)	[6]	(116,101)	[6]
Accumulated other comprehensive loss	(42,135)	[6]	(26,143)	[6]
Retained earnings	(214,104)	[6]	(191,584)	[6]
Unearned employee stock ownership plan shares	0		0
Total stockholders' equity	(379,641)		(339,629)
Total liabilities and stockholders' equity	(391,167)		(349,686)
Eliminations | Rental trailers and other rental equipment
Property, plant and equipment, at cost:
Property subject to or available for operating lease, gross	0		0
Eliminations | Rental trucks
Property, plant and equipment, at cost:
Property subject to or available for operating lease, gross	0		0
Eliminations | Series A preferred stock
Stockholders' equity:
Preferred stock, value, issued	0		0
Eliminations | Series B preferred stock
Stockholders' equity:
Preferred stock, value, issued	0		0
Eliminations | Series A common stock
Stockholders' equity:
Common stock, value, issued	0		0
Eliminations | Common stock
Stockholders' equity:
Common stock, value, issued	(5,801)	[6]	(5,801)	[6]
Eliminations | Cost of common shares in treasury, net
Stockholders' equity:
Treasury stock, value	0		0
Eliminations | Cost of preferred shares in treasury, net
Stockholders' equity:
Treasury stock, value	0		0
Moving and Storage Operating Segment
ASSETS:
Cash and cash equivalents	427,560		309,228		323,495		207,705
Reinsurance recoverables and trade receivables, net	43,259		37,103
Inventories, net	56,396		58,735
Prepaid expenses	57,451		41,858
Investments, fixed maturities and marketable equities	21,228		17,028
Investments, other	50,653		52,333
Deferred policy acquisition costs, net	0		0
Other assets	98,617		118,815
Related party assets	184,201		318,190
Subtotal assets	939,365		953,290
Investments in subsidiaries	379,641		339,629
Property, plant and equipment, at cost:
Land	333,228		281,140
Buildings and improvements	1,197,875		1,087,119
Furniture and equipment	311,142		308,120
Property, plant and equipment (gross)	4,314,409		3,787,822
Less: Accumulated depreciation	(1,559,355)		(1,415,457)
Total property, plant and equipment	2,755,054		2,372,365
Total assets	4,074,060		3,665,284
Liabilities:
Accounts payable and accrued expenses	350,352		325,266
Notes, loans and leases payable	1,661,845		1,486,211
Policy benefits and losses, claims and loss expenses payable	380,824		380,140
Liabilities from investment contracts	0		0
Other policyholders' funds and liabilities	0		0
Deferred income	30,217		31,525
Deferred income taxes	412,089		397,992
Related party liabilities	9,474		8,330
Total liabilities	2,844,801		2,629,464
Stockholders' equity:
Additional paid-in capital	438,378		433,953
Accumulated other comprehensive loss	(22,680)		(45,436)
Retained earnings	1,482,420		1,316,854
Unearned employee stock ownership plan shares	(1,706)		(2,398)
Total stockholders' equity	1,229,259		1,035,820
Total liabilities and stockholders' equity	4,074,060		3,665,284
Moving and Storage Operating Segment | Rental trailers and other rental equipment
Property, plant and equipment, at cost:
Property subject to or available for operating lease, gross	317,476		255,010
Moving and Storage Operating Segment | Rental trucks
Property, plant and equipment, at cost:
Property subject to or available for operating lease, gross	2,154,688		1,856,433
Moving and Storage Operating Segment | Series A preferred stock
Stockholders' equity:
Preferred stock, value, issued	0		0
Moving and Storage Operating Segment | Series B preferred stock
Stockholders' equity:
Preferred stock, value, issued	0		0
Moving and Storage Operating Segment | Series A common stock
Stockholders' equity:
Common stock, value, issued	0		0
Moving and Storage Operating Segment | Common stock
Stockholders' equity:
Common stock, value, issued	10,497		10,497
Moving and Storage Operating Segment | Cost of common shares in treasury, net
Stockholders' equity:
Treasury stock, value	(525,653)		(525,653)
Moving and Storage Operating Segment | Cost of preferred shares in treasury, net
Stockholders' equity:
Treasury stock, value	(151,997)		(151,997)
AMERCO
ASSETS:
Cash and cash equivalents	327,119		201,502		250,104		100,460
Reinsurance recoverables and trade receivables, net	0		0
Inventories, net	0		0
Prepaid expenses	22,475		9,496
Investments, fixed maturities and marketable equities	21,228		17,028
Investments, other	0		0
Deferred policy acquisition costs, net	0		0
Other assets	118		483
Related party assets	1,032,124		1,201,385
Subtotal assets	1,403,064		1,429,894
Investments in subsidiaries	240,080		8,168
Property, plant and equipment, at cost:
Land	0		0
Buildings and improvements	0		0
Furniture and equipment	136		138
Property, plant and equipment (gross)	136		138
Less: Accumulated depreciation	(116)		(115)
Total property, plant and equipment	20		23
Total assets	1,643,164		1,438,085
Liabilities:
Accounts payable and accrued expenses	110		1,875
Notes, loans and leases payable	0		0
Policy benefits and losses, claims and loss expenses payable	0		0
Liabilities from investment contracts	0		0
Other policyholders' funds and liabilities	0		0
Deferred income	0		0
Deferred income taxes	412,089		397,992
Related party liabilities	0		0
Total liabilities	412,199		399,867
Stockholders' equity:
Additional paid-in capital	438,378		433,953
Accumulated other comprehensive loss	(22,680)		(45,436)
Retained earnings	1,482,420		1,316,854		1,139,792
Unearned employee stock ownership plan shares	0		0
Total stockholders' equity	1,230,965		1,038,218
Total liabilities and stockholders' equity	1,643,164		1,438,085
AMERCO | Rental trailers and other rental equipment
Property, plant and equipment, at cost:
Property subject to or available for operating lease, gross	0		0
AMERCO | Rental trucks
Property, plant and equipment, at cost:
Property subject to or available for operating lease, gross	0		0
AMERCO | Series A preferred stock
Stockholders' equity:
Preferred stock, value, issued	0		0
AMERCO | Series B preferred stock
Stockholders' equity:
Preferred stock, value, issued	0		0
AMERCO | Series A common stock
Stockholders' equity:
Common stock, value, issued	0		0
AMERCO | Common stock
Stockholders' equity:
Common stock, value, issued	10,497		10,497
AMERCO | Cost of common shares in treasury, net
Stockholders' equity:
Treasury stock, value	(525,653)		(525,653)
AMERCO | Cost of preferred shares in treasury, net
Stockholders' equity:
Treasury stock, value	(151,997)		(151,997)
U-Haul
ASSETS:
Cash and cash equivalents	98,926		106,951		72,634		107,241
Reinsurance recoverables and trade receivables, net	43,259		37,103
Inventories, net	56,396		58,735
Prepaid expenses	34,956		32,051
Investments, fixed maturities and marketable equities	0		0
Investments, other	100		9,880
Deferred policy acquisition costs, net	0		0
Other assets	69,671		91,761
Related party assets	127,751		261,341
Subtotal assets	431,059		597,822
Investments in subsidiaries	(539)		0
Property, plant and equipment, at cost:
Land	81,421		67,558
Buildings and improvements	184,053		162,351
Furniture and equipment	292,621		289,601
Property, plant and equipment (gross)	3,030,259		2,630,953
Less: Accumulated depreciation	(1,185,796)		(1,056,854)
Total property, plant and equipment	1,844,463		1,574,099
Total assets	2,274,983		2,171,921
Liabilities:
Accounts payable and accrued expenses	345,864		319,780
Notes, loans and leases payable	881,766		769,497
Policy benefits and losses, claims and loss expenses payable	380,824		380,140
Liabilities from investment contracts	0		0
Other policyholders' funds and liabilities	0		0
Deferred income	30,217		31,525
Deferred income taxes	0		0
Related party liabilities	637,909		855,016
Total liabilities	2,276,580		2,355,958
Stockholders' equity:
Additional paid-in capital	121,230		121,230
Accumulated other comprehensive loss	(62,325)		(66,302)
Retained earnings	(58,797)		(237,107)
Unearned employee stock ownership plan shares	(1,706)		(2,398)
Total stockholders' equity	(1,597)		(184,037)
Total liabilities and stockholders' equity	2,274,983		2,171,921
U-Haul | Rental trailers and other rental equipment
Property, plant and equipment, at cost:
Property subject to or available for operating lease, gross	317,476		255,010
U-Haul | Rental trucks
Property, plant and equipment, at cost:
Property subject to or available for operating lease, gross	2,154,688		1,856,433
U-Haul | Series A preferred stock
Stockholders' equity:
Preferred stock, value, issued	0		0
U-Haul | Series B preferred stock
Stockholders' equity:
Preferred stock, value, issued	0		0
U-Haul | Series A common stock
Stockholders' equity:
Common stock, value, issued	0		0
U-Haul | Common stock
Stockholders' equity:
Common stock, value, issued	1		540
U-Haul | Cost of common shares in treasury, net
Stockholders' equity:
Treasury stock, value	0		0
U-Haul | Cost of preferred shares in treasury, net
Stockholders' equity:
Treasury stock, value	0		0
Real Estate
ASSETS:
Cash and cash equivalents	1,515		775		757		4
Reinsurance recoverables and trade receivables, net	0		0
Inventories, net	0		0
Prepaid expenses	20		311
Investments, fixed maturities and marketable equities	0		0
Investments, other	50,553		42,453
Deferred policy acquisition costs, net	0		0
Other assets	28,828		26,571
Related party assets	9		9
Subtotal assets	80,925		70,119
Investments in subsidiaries	0		0
Property, plant and equipment, at cost:
Land	251,807		213,582
Buildings and improvements	1,013,822		924,768
Furniture and equipment	18,385		18,381
Property, plant and equipment (gross)	1,284,014		1,156,731
Less: Accumulated depreciation	(373,443)		(358,488)
Total property, plant and equipment	910,571		798,243
Total assets	991,496		868,362
Liabilities:
Accounts payable and accrued expenses	4,378		3,611
Notes, loans and leases payable	780,079		716,714
Policy benefits and losses, claims and loss expenses payable	0		0
Liabilities from investment contracts	0		0
Other policyholders' funds and liabilities	0		0
Deferred income	0		0
Deferred income taxes	0		0
Related party liabilities	347,248		297,859
Total liabilities	1,131,705		1,018,184
Stockholders' equity:
Additional paid-in capital	147,941		147,941
Accumulated other comprehensive loss	0		0
Retained earnings	(288,151)		(297,764)
Unearned employee stock ownership plan shares	0		0
Total stockholders' equity	(140,209)		(149,822)
Total liabilities and stockholders' equity	991,496		868,362
Real Estate | Rental trailers and other rental equipment
Property, plant and equipment, at cost:
Property subject to or available for operating lease, gross	0		0
Real Estate | Rental trucks
Property, plant and equipment, at cost:
Property subject to or available for operating lease, gross	0		0
Real Estate | Series A preferred stock
Stockholders' equity:
Preferred stock, value, issued	0		0
Real Estate | Series B preferred stock
Stockholders' equity:
Preferred stock, value, issued	0		0
Real Estate | Series A common stock
Stockholders' equity:
Common stock, value, issued	0		0
Real Estate | Common stock
Stockholders' equity:
Common stock, value, issued	1		1
Real Estate | Cost of common shares in treasury, net
Stockholders' equity:
Treasury stock, value	0		0
Real Estate | Cost of preferred shares in treasury, net
Stockholders' equity:
Treasury stock, value	0		0
Eliminations
ASSETS:
Cash and cash equivalents	0		0		0		0
Reinsurance recoverables and trade receivables, net	0		0
Inventories, net	0		0
Prepaid expenses	0		0
Investments, fixed maturities and marketable equities	0		0
Investments, other	0		0
Deferred policy acquisition costs, net	0		0
Other assets	0		0
Related party assets	(975,683)	[5]	(1,144,545)	[5]
Subtotal assets	(975,683)		(1,144,545)
Investments in subsidiaries	140,100	[6]	331,461	[6]
Property, plant and equipment, at cost:
Land	0		0
Buildings and improvements	0		0
Furniture and equipment	0		0
Property, plant and equipment (gross)	0		0
Less: Accumulated depreciation	0		0
Total property, plant and equipment	0		0
Total assets	(835,583)		(813,084)
Liabilities:
Accounts payable and accrued expenses	0		0
Notes, loans and leases payable	0		0
Policy benefits and losses, claims and loss expenses payable	0		0
Liabilities from investment contracts	0		0
Other policyholders' funds and liabilities	0		0
Deferred income	0		0
Deferred income taxes	0		0
Related party liabilities	(975,683)	[5]	(1,144,545)	[5]
Total liabilities	(975,683)		(1,144,545)
Stockholders' equity:
Additional paid-in capital	(269,171)	[6]	(269,171)	[6]
Accumulated other comprehensive loss	62,325	[6]	66,302	[6]
Retained earnings	346,948	[6]	534,871	[6]
Unearned employee stock ownership plan shares	0		0
Total stockholders' equity	140,100		331,461
Total liabilities and stockholders' equity	(835,583)		(813,084)
Eliminations | Rental trailers and other rental equipment
Property, plant and equipment, at cost:
Property subject to or available for operating lease, gross	0		0
Eliminations | Rental trucks
Property, plant and equipment, at cost:
Property subject to or available for operating lease, gross	0		0
Eliminations | Series A preferred stock
Stockholders' equity:
Preferred stock, value, issued	0		0
Eliminations | Series B preferred stock
Stockholders' equity:
Preferred stock, value, issued	0		0
Eliminations | Series A common stock
Stockholders' equity:
Common stock, value, issued	0		0
Eliminations | Common stock
Stockholders' equity:
Common stock, value, issued	(2)	[6]	(541)	[6]
Eliminations | Cost of common shares in treasury, net
Stockholders' equity:
Treasury stock, value	0		0
Eliminations | Cost of preferred shares in treasury, net
Stockholders' equity:
Treasury stock, value	$ 0		$ 0

[1] Balance as of December 31, 2012

[2] Balances as of December 31, 2011

[3] Balance for the period ended December 31, 2011

[4] Balance for the period ended December 31, 2010

[5] Eliminate intercompany receivables and payables

[6] Eliminate investment in subsidiaries