Consolidated Balance Sheet by Industry Segment (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012		Mar. 31, 2012		Dec. 31, 2011		Mar. 31, 2011
ASSETS:
Cash and cash equivalents	$ 586,124		$ 357,180		$ 445,343		$ 382,514
Reinsurance recoverables and trade receivables, net	226,340		297,974
Inventories, net	55,989		58,735
Prepaid expenses	55,148		41,858
Investments, fixed maturities and marketable equities	1,019,968		766,792
Investments, other	270,191		258,551
Deferred policy acquisition costs, net	93,533		63,914
Other assets	101,889		120,525
Related party assets	175,175		316,157
Subtotal assets	2,584,357		2,281,686
Property, plant and equipment, at cost:
Land	338,598		281,140
Buildings and improvements	1,155,754		1,087,119
Furniture and equipment	316,772		308,120
Property, plant and equipment (gross)	4,159,142		3,787,822
Less: Accumulated depreciation	(1,524,194)		(1,415,457)
Total property, plant and equipment	2,634,948		2,372,365
Total assets	5,219,305		4,654,051		4,634,002
Liabilities:
Accounts payable and accrued expenses	326,182		335,326
Notes, loans and leases payable	1,667,008		1,486,211
Policy benefits and losses, claims and loss expenses payable	1,115,823		1,145,943
Liabilities from investment contracts	486,502		240,961
Other policyholders' funds and liabilities	6,348		7,273
Deferred income	27,840		31,525
Deferred income taxes	399,103		370,992
Total liabilities	4,028,806		3,618,231
Stockholders' equity:
Additional paid-in capital	436,926		433,743
Accumulated other comprehensive loss	(22,192)		(45,436)
Retained earnings	1,444,757		1,317,064
Unearned employee stock ownership plan shares	(1,839)		(2,398)
Total stockholders' equity	1,190,499		1,035,820
Total liabilities and stockholders' equity	5,219,305		4,654,051
Property and Casualty Insurance
ASSETS:
Cash and cash equivalents	14,490	[1]	22,542	[2]	26,351	[3]	21,718	[3]
Reinsurance recoverables and trade receivables, net	172,370	[1]	231,211	[2]
Inventories, net	0	[1]	0	[2]
Prepaid expenses	0	[1]	0	[2]
Investments, fixed maturities and marketable equities	123,777	[1]	132,270	[2]
Investments, other	101,495	[1]	74,757	[2]
Deferred policy acquisition costs, net	0	[1]	0	[2]
Other assets	487	[1]	1,507	[2]
Related party assets	8,738	[1]	7,542	[2]
Subtotal assets	421,357	[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],[4],[5]
Total assets	421,357	[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	322,548	[1]	382,939	[2]
Liabilities from investment contracts	0	[1]	0	[2]
Other policyholders' funds and liabilities	2,853	[1]	3,438	[2]
Deferred income	0	[1]	0	[2]
Deferred income taxes	(39,054)	[1]	(41,945)	[2]
Related party liabilities	2,181	[1]	1,555	[2]
Total liabilities	288,528	[1]	345,987	[2]
Stockholders' equity:
Additional paid-in capital	91,120	[1]	89,620	[2]
Accumulated other comprehensive loss	5,198	[1]	2,255	[2]
Retained earnings	33,210	[1]	28,666	[2]
Unearned employee stock ownership plan shares	0	[1]	0	[2]
Total stockholders' equity	132,829	[1]	123,842	[2]
Total liabilities and stockholders' equity	421,357	[1]	469,829	[2]
Life Insurance
ASSETS:
Cash and cash equivalents	32,751	[1]	25,410	[2]	12,729	[3]	37,301	[3]
Reinsurance recoverables and trade receivables, net	29,088	[1]	29,660	[2]
Inventories, net	0	[1]	0	[2]
Prepaid expenses	0	[1]	0	[2]
Investments, fixed maturities and marketable equities	875,719	[1]	617,494	[2]
Investments, other	125,571	[1]	131,461	[2]
Deferred policy acquisition costs, net	93,533	[1]	63,914	[2]
Other assets	214	[1]	203	[2]
Related party assets	516	[1]	482	[2]
Subtotal assets	1,157,392	[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	1,157,392	[1]	868,624	[2]
Liabilities:
Accounts payable and accrued expenses	5,579	[1]	10,060	[2]
Notes, loans and leases payable	0	[1]	0	[2]
Policy benefits and losses, claims and loss expenses payable	404,549	[1]	382,864	[2]
Liabilities from investment contracts	486,502	[1]	240,961	[2]
Other policyholders' funds and liabilities	3,495	[1]	3,835	[2]
Deferred income	0	[1]	0	[2]
Deferred income taxes	19,265	[1]	14,945	[2]
Related party liabilities	655	[1]	172	[2]
Total liabilities	920,045	[1]	652,837	[2]
Stockholders' equity:
Additional paid-in capital	26,271	[1]	26,271	[2]
Accumulated other comprehensive loss	38,801	[1]	23,888	[2]
Retained earnings	169,775	[1]	163,128	[2]
Unearned employee stock ownership plan shares	0	[1]	0	[2]
Total stockholders' equity	237,347	[1]	215,787	[2]
Total liabilities and stockholders' equity	1,157,392	[1]	868,624	[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	(12,231)	[6]	(10,057)	[6]
Subtotal assets	(12,231)		(10,057)
Investments in subsidiaries	(370,176)	[7]	(339,629)	[7]
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	(382,407)		(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	(12,231)	[6]	(10,057)	[6]
Total liabilities	(12,231)		(10,057)
Stockholders' equity:
Additional paid-in capital	(117,601)	[7]	(116,101)	[7]
Accumulated other comprehensive loss	(43,999)	[7]	(26,143)	[7]
Retained earnings	(202,775)	[7]	(191,584)	[7]
Unearned employee stock ownership plan shares	0		0
Total stockholders' equity	(370,176)		(339,629)
Total liabilities and stockholders' equity	(382,407)		(349,686)
Moving and Storage Consolidations
ASSETS:
Cash and cash equivalents	538,883		309,228		406,263		323,495
Reinsurance recoverables and trade receivables, net	24,882		37,103
Inventories, net	55,989		58,735
Prepaid expenses	55,148		41,858
Investments, fixed maturities and marketable equities	20,472		17,028
Investments, other	43,125		52,333
Deferred policy acquisition costs, net	0		0
Other assets	101,188		118,815
Related party assets	178,152		318,190
Subtotal assets	1,017,839		953,290
Investments in subsidiaries	370,176		339,629
Property, plant and equipment, at cost:
Land	338,598		281,140
Buildings and improvements	1,155,754		1,087,119
Furniture and equipment	316,772		308,120
Property, plant and equipment (gross)	4,159,142		3,787,822
Less: Accumulated depreciation	(1,524,194)		(1,415,457)
Total property, plant and equipment	2,634,948		2,372,365
Total assets	4,022,963		3,665,284
Liabilities:
Accounts payable and accrued expenses	320,603		325,266
Notes, loans and leases payable	1,667,008		1,486,211
Policy benefits and losses, claims and loss expenses payable	388,726		380,140
Liabilities from investment contracts	0		0
Other policyholders' funds and liabilities	0		0
Deferred income	27,840		31,525
Deferred income taxes	418,892		397,992
Related party liabilities	9,395		8,330
Total liabilities	2,832,464		2,629,464
Stockholders' equity:
Additional paid-in capital	437,136		433,953
Accumulated other comprehensive loss	(22,192)		(45,436)
Retained earnings	1,444,547		1,316,854
Unearned employee stock ownership plan shares	(1,839)		(2,398)
Total stockholders' equity	1,190,499		1,035,820
Total liabilities and stockholders' equity	4,022,963		3,665,284
AMERCO /NV/
ASSETS:
Cash and cash equivalents	351,755		201,502		289,497		250,104
Reinsurance recoverables and trade receivables, net	0		0
Inventories, net	0		0
Prepaid expenses	12,578		9,496
Investments, fixed maturities and marketable equities	20,472		17,028
Investments, other	0		0
Deferred policy acquisition costs, net	0		0
Other assets	480		483
Related party assets	1,008,820		1,201,385
Subtotal assets	1,394,105		1,429,894
Investments in subsidiaries	217,615		8,168
Property, plant and equipment, at cost:
Land	0		0
Buildings and improvements	0		0
Furniture and equipment	140		138
Property, plant and equipment (gross)	140		138
Less: Accumulated depreciation	(119)		(115)
Total property, plant and equipment	21		23
Total assets	1,611,741		1,438,085
Liabilities:
Accounts payable and accrued expenses	511		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	418,892		397,992
Related party liabilities	0		0
Total liabilities	419,403		399,867
Stockholders' equity:
Additional paid-in capital	437,136		433,953
Accumulated other comprehensive loss	(22,192)		(45,436)
Retained earnings	1,444,547		1,316,854
Unearned employee stock ownership plan shares	0		0
Total stockholders' equity	1,192,338		1,038,218
Total liabilities and stockholders' equity	1,611,741		1,438,085
U-Haul
ASSETS:
Cash and cash equivalents	185,624		106,951		115,999		72,634
Reinsurance recoverables and trade receivables, net	24,882		37,103
Inventories, net	55,989		58,735
Prepaid expenses	42,030		32,051
Investments, fixed maturities and marketable equities	0		0
Investments, other	0		9,880
Deferred policy acquisition costs, net	0		0
Other assets	71,517		91,761
Related party assets	121,303		261,341
Subtotal assets	501,345		597,822
Investments in subsidiaries	0		0
Property, plant and equipment, at cost:
Land	106,859		67,558
Buildings and improvements	182,051		162,351
Furniture and equipment	298,282		289,601
Property, plant and equipment (gross)	2,935,210		2,630,953
Less: Accumulated depreciation	(1,154,751)		(1,056,854)
Total property, plant and equipment	1,780,459		1,574,099
Total assets	2,281,804		2,171,921
Liabilities:
Accounts payable and accrued expenses	315,935		319,780
Notes, loans and leases payable	880,542		769,497
Policy benefits and losses, claims and loss expenses payable	388,726		380,140
Liabilities from investment contracts	0		0
Other policyholders' funds and liabilities	0		0
Deferred income	27,840		31,525
Deferred income taxes	0		0
Related party liabilities	679,544		855,016
Total liabilities	2,292,587		2,355,958
Stockholders' equity:
Additional paid-in capital	121,230		121,230
Accumulated other comprehensive loss	(63,049)		(66,302)
Retained earnings	(67,665)		(237,107)
Unearned employee stock ownership plan shares	(1,839)		(2,398)
Total stockholders' equity	(10,783)		(184,037)
Total liabilities and stockholders' equity	2,281,804		2,171,921
Real Estate
ASSETS:
Cash and cash equivalents	1,504		775		767		757
Reinsurance recoverables and trade receivables, net	0		0
Inventories, net	0		0
Prepaid expenses	540		311
Investments, fixed maturities and marketable equities	0		0
Investments, other	43,125		42,453
Deferred policy acquisition costs, net	0		0
Other assets	29,191		26,571
Related party assets	7		9
Subtotal assets	74,367		70,119
Investments in subsidiaries	0		0
Property, plant and equipment, at cost:
Land	231,739		213,582
Buildings and improvements	973,703		924,768
Furniture and equipment	18,350		18,381
Property, plant and equipment (gross)	1,223,792		1,156,731
Less: Accumulated depreciation	(369,324)		(358,488)
Total property, plant and equipment	854,468		798,243
Total assets	928,835		868,362
Liabilities:
Accounts payable and accrued expenses	4,157		3,611
Notes, loans and leases payable	786,466		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	281,829		297,859
Total liabilities	1,072,452		1,018,184
Stockholders' equity:
Additional paid-in capital	147,941		147,941
Accumulated other comprehensive loss	0		0
Retained earnings	(291,559)		(297,764)
Unearned employee stock ownership plan shares	0		0
Total stockholders' equity	(143,617)		(149,822)
Total liabilities and stockholders' equity	928,835		868,362
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	(951,978)	[6]	(1,144,545)	[6]
Subtotal assets	(951,978)		(1,144,545)
Investments in subsidiaries	152,561	[7]	331,461	[7]
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	(799,417)		(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	(951,978)	[6]	(1,144,545)	[6]
Total liabilities	(951,978)		(1,144,545)
Stockholders' equity:
Additional paid-in capital	(269,171)	[7]	(269,171)	[7]
Accumulated other comprehensive loss	63,049	[7]	66,302	[7]
Retained earnings	359,224	[7]	534,871	[7]
Unearned employee stock ownership plan shares	0		0
Total stockholders' equity	152,561		331,461
Total liabilities and stockholders' equity	(799,417)		(813,084)
Rental trailers and other rental equipment
Property, plant and equipment, at cost:
Property subject to or available for operating lease, gross	303,379		255,010
Rental trailers and other rental equipment | Property and Casualty Insurance
Property, plant and equipment, at cost:
Property subject to or available for operating lease, gross	0	[1]	0	[2]
Rental trailers and other rental equipment | Life Insurance
Property, plant and equipment, at cost:
Property subject to or available for operating lease, gross	0	[1]	0	[2]
Rental trailers and other rental equipment | Eliminations
Property, plant and equipment, at cost:
Property subject to or available for operating lease, gross	0		0
Rental trailers and other rental equipment | Moving and Storage Consolidations
Property, plant and equipment, at cost:
Property subject to or available for operating lease, gross	303,379		255,010
Rental trailers and other rental equipment | AMERCO /NV/
Property, plant and equipment, at cost:
Property subject to or available for operating lease, gross	0		0
Rental trailers and other rental equipment | U-Haul
Property, plant and equipment, at cost:
Property subject to or available for operating lease, gross	303,379		255,010
Rental trailers and other rental equipment | Real Estate
Property, plant and equipment, at cost:
Property subject to or available for operating lease, gross	0		0
Rental trailers and other rental equipment | Eliminations
Property, plant and equipment, at cost:
Property subject to or available for operating lease, gross	0		0
Rental trucks
Property, plant and equipment, at cost:
Property subject to or available for operating lease, gross	2,044,639		1,856,433
Rental trucks | Property and Casualty Insurance
Property, plant and equipment, at cost:
Property subject to or available for operating lease, gross	0	[1]	0	[2]
Rental trucks | Life Insurance
Property, plant and equipment, at cost:
Property subject to or available for operating lease, gross	0	[1]	0	[2]
Rental trucks | Eliminations
Property, plant and equipment, at cost:
Property subject to or available for operating lease, gross	0		0
Rental trucks | Moving and Storage Consolidations
Property, plant and equipment, at cost:
Property subject to or available for operating lease, gross	2,044,639		1,856,433
Rental trucks | AMERCO /NV/
Property, plant and equipment, at cost:
Property subject to or available for operating lease, gross	0		0
Rental trucks | U-Haul
Property, plant and equipment, at cost:
Property subject to or available for operating lease, gross	2,044,639		1,856,433
Rental trucks | Real Estate
Property, plant and equipment, at cost:
Property subject to or available for operating lease, gross	0		0
Rental trucks | Eliminations
Property, plant and equipment, at cost:
Property subject to or available for operating lease, gross	0		0
Series A preferred stock
Stockholders' equity:
Preferred stock, value, issued
Series A preferred stock | Property and Casualty Insurance
Stockholders' equity:
Preferred stock, value, issued	0	[1]	0	[2]
Series A preferred stock | Life Insurance
Stockholders' equity:
Preferred stock, value, issued	0	[1]	0	[2]
Series A preferred stock | Eliminations
Stockholders' equity:
Preferred stock, value, issued	0		0
Series A preferred stock | Moving and Storage Consolidations
Stockholders' equity:
Preferred stock, value, issued	0		0
Series A preferred stock | AMERCO /NV/
Stockholders' equity:
Preferred stock, value, issued	0		0
Series A preferred stock | U-Haul
Stockholders' equity:
Preferred stock, value, issued	0		0
Series A preferred stock | Real Estate
Stockholders' equity:
Preferred stock, value, issued	0		0
Series A preferred stock | Eliminations
Stockholders' equity:
Preferred stock, value, issued	0		0
Series B preferred stock
Stockholders' equity:
Preferred stock, value, issued
Series B preferred stock | Property and Casualty Insurance
Stockholders' equity:
Preferred stock, value, issued	0	[1]	0	[2]
Series B preferred stock | Life Insurance
Stockholders' equity:
Preferred stock, value, issued	0	[1]	0	[2]
Series B preferred stock | Eliminations
Stockholders' equity:
Preferred stock, value, issued	0		0
Series B preferred stock | Moving and Storage Consolidations
Stockholders' equity:
Preferred stock, value, issued	0		0
Series B preferred stock | AMERCO /NV/
Stockholders' equity:
Preferred stock, value, issued	0		0
Series B preferred stock | U-Haul
Stockholders' equity:
Preferred stock, value, issued	0		0
Series B preferred stock | Real Estate
Stockholders' equity:
Preferred stock, value, issued	0		0
Series B preferred stock | Eliminations
Stockholders' equity:
Preferred stock, value, issued	0		0
Series A common stock
Stockholders' equity:
Common stock, value, issued
Series A common stock | Property and Casualty Insurance
Stockholders' equity:
Common stock, value, issued	0	[1]	0	[2]
Series A common stock | Life Insurance
Stockholders' equity:
Common stock, value, issued	0	[1]	0	[2]
Series A common stock | Eliminations
Stockholders' equity:
Common stock, value, issued	0		0
Series A common stock | Moving and Storage Consolidations
Stockholders' equity:
Common stock, value, issued	0		0
Series A common stock | AMERCO /NV/
Stockholders' equity:
Common stock, value, issued	0		0
Series A common stock | U-Haul
Stockholders' equity:
Common stock, value, issued	0		0
Series A common stock | Real Estate
Stockholders' equity:
Common stock, value, issued	0		0
Series A common stock | Eliminations
Stockholders' equity:
Common stock, value, issued	0		0
Common stock
Stockholders' equity:
Common stock, value, issued	10,497		10,497
Common stock | Property and Casualty Insurance
Stockholders' equity:
Common stock, value, issued	3,301	[1]	3,301	[2]
Common stock | Life Insurance
Stockholders' equity:
Common stock, value, issued	2,500	[1]	2,500	[2]
Common stock | Eliminations
Stockholders' equity:
Common stock, value, issued	(5,801)	[7]	(5,801)	[7]
Common stock | Moving and Storage Consolidations
Stockholders' equity:
Common stock, value, issued	10,497		10,497
Common stock | AMERCO /NV/
Stockholders' equity:
Common stock, value, issued	10,497		10,497
Common stock | U-Haul
Stockholders' equity:
Common stock, value, issued	540		540
Common stock | Real Estate
Stockholders' equity:
Common stock, value, issued	1		1
Common stock | Eliminations
Stockholders' equity:
Common stock, value, issued	(541)	[7]	(541)	[7]
Cost of common shares in treasury, net
Stockholders' equity:
Treasury stock, value	(525,653)		(525,653)
Cost of common shares in treasury, net | Property and Casualty Insurance
Stockholders' equity:
Treasury stock, value	0	[1]	0	[2]
Cost of common shares in treasury, net | Life Insurance
Stockholders' equity:
Treasury stock, value	0	[1]	0	[2]
Cost of common shares in treasury, net | Eliminations
Stockholders' equity:
Treasury stock, value	0		0
Cost of common shares in treasury, net | Moving and Storage Consolidations
Stockholders' equity:
Treasury stock, value	(525,653)		(525,653)
Cost of common shares in treasury, net | AMERCO /NV/
Stockholders' equity:
Treasury stock, value	(525,653)		(525,653)
Cost of common shares in treasury, net | U-Haul
Stockholders' equity:
Treasury stock, value	0		0
Cost of common shares in treasury, net | Real Estate
Stockholders' equity:
Treasury stock, value	0		0
Cost of common shares in treasury, net | Eliminations
Stockholders' equity:
Treasury stock, value	0		0
Cost of preferred shares in treasury, net
Stockholders' equity:
Treasury stock, value	(151,997)		(151,997)
Cost of preferred shares in treasury, net | Property and Casualty Insurance
Stockholders' equity:
Treasury stock, value	0	[1]	0	[2]
Cost of preferred shares in treasury, net | Life Insurance
Stockholders' equity:
Treasury stock, value	0	[1]	0	[2]
Cost of preferred shares in treasury, net | Eliminations
Stockholders' equity:
Treasury stock, value	0		0
Cost of preferred shares in treasury, net | Moving and Storage Consolidations
Stockholders' equity:
Treasury stock, value	(151,997)		(151,997)
Cost of preferred shares in treasury, net | AMERCO /NV/
Stockholders' equity:
Treasury stock, value	(151,997)		(151,997)
Cost of preferred shares in treasury, net | U-Haul
Stockholders' equity:
Treasury stock, value	0		0
Cost of preferred shares in treasury, net | Real Estate
Stockholders' equity:
Treasury stock, value	0		0
Cost of preferred shares in treasury, net | Eliminations
Stockholders' equity:
Treasury stock, value	$ 0		$ 0

[1] Balances as of September 30, 2012

[2] Balances as of December 31, 2011

[3] Balance for the nine months ended September 30, 2011

[4] Eliminate intercompany premiums

[5] Eliminate intercompany lease / interest income

[6] Eliminate intercompany receivables and payables

[7] Eliminate investment in subsidiaries