Consolidating Financial Information By Industry Segment (Table Text Block)	3 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
Table Text Block Supplement [Abstract]
Consolidated Balance Sheet by Industry Segment	Consolidating balance sheets by industry segment as of June 30, 2021 are as follows:       Moving & Storage Consolidated   Property & Casualty Insurance (a)   Life Insurance (a)   Eliminations     AMERCO Consolidated     (Unaudited)     (In thousands) Assets:   Cash and cash equivalents $ 1,455,973 $ 3,246 $ 60,762 $ –   $ 1,519,981 Reinsurance recoverables and trade receivables, net   120,946   67,589   44,521   –     233,056 Inventories and parts, net   117,978   –   –   –     117,978 Prepaid expenses   306,565   –   –   –     306,565 Investments, fixed maturities and marketable equities   –   290,571   2,464,562   –     2,755,133 Investments, other   20,733   94,028   411,132   –     525,893 Deferred policy acquisition costs, net   –   –   101,169   –     101,169 Other assets   43,439   829   2,642   –     46,910 Right of use assets - financing, net   814,875   –   –   –     814,875 Right of use assets - operating, net   89,034   184   151   –     89,369 Related party assets   53,783   6,557   13,797   (39,656) (c)   34,481     3,023,326   463,004   3,098,736   (39,656)     6,545,410                         Investment in subsidiaries   677,909   –   –   (677,909) (b)   –                         Property, plant and equipment, at cost:                       Land   1,110,300   –   –   –     1,110,300 Buildings and improvements   5,284,224   –   –   –     5,284,224 Furniture and equipment   796,077   –   –   –     796,077 Rental trailers and other rental equipment   495,012   –   –   –     495,012 Rental trucks   4,119,655   –   –   –     4,119,655     11,805,268   –   –   –     11,805,268 Less:   Accumulated depreciation   (3,235,796)   –   –   –     (3,235,796) Total property, plant and equipment, net   8,569,472   –   –   –     8,569,472 Total assets $ 12,270,707 $ 463,004 $ 3,098,736 $ (717,565)   $ 15,114,882                         (a) Balances as of March 31, 2021                       (b) Eliminate investment in subsidiaries                       (c) Eliminate intercompany receivables and payables                         Consolidating balance sheets by industry segment as of June 30, 2021, continued       Moving & Storage Consolidated   Property & Casualty Insurance (a)   Life Insurance (a)   Eliminations     AMERCO Consolidated     (Unaudited)     (In thousands) Liabilities:                       Accounts payable and accrued expenses $ 679,461 $ 2,260 $ 15,076 $ –   $ 696,797 Notes, loans and finance leases payable, net   4,662,325   –   11,058   –     4,673,383 Operating lease liability   89,042   188   160   –     89,390 Policy benefits and losses, claims and loss expenses payable   433,394   179,294   394,456   –     1,007,144 Liabilities from investment contracts   –   –   2,226,560   –     2,226,560 Other policyholders' funds and liabilities   –   3,237   7,752   –     10,989 Deferred income   54,738   –   –   –     54,738 Deferred income taxes, net   1,217,716   11,667   14,970   –     1,244,353 Related party liabilities   26,836   3,812   13,341   (43,989) (c)   – Total liabilities   7,163,512   200,458   2,683,373   (43,989)     10,003,354                         Stockholders' equity:                       Series preferred stock:                       Series A preferred stock   –   –   –   –     – Series B preferred stock   –   –   –   –     – Series A common stock   –   –   –   –     – Common stock   10,497   3,301   2,500   (5,801) (b)   10,497 Additional paid-in capital   454,029   91,120   26,271   (117,601) (b)   453,819 Accumulated other comprehensive income (loss)   26,799   15,148   75,145   (85,960) (b)   31,132 Retained earnings   5,293,520   152,977   311,447   (464,214) (b)   5,293,730 Cost of common stock in treasury, net   (525,653)   –   –   –     (525,653) Cost of preferred stock in treasury, net   (151,997)   –   –   –     (151,997) Total stockholders' equity   5,107,195   262,546   415,363   (673,576)     5,111,528 Total liabilities and stockholders' equity $ 12,270,707 $ 463,004 $ 3,098,736 $ (717,565)   $ 15,114,882                         (a) Balances as of March 31, 2021                       (b) Eliminate investment in subsidiaries                       (c) Eliminate intercompany receivables and payables                           Consolidating balance sheets by industry segment as of March 31, 2021 are as follows:       Moving & Storage Consolidated   Property & Casualty Insurance (a)   Life Insurance (a)   Eliminations     AMERCO Consolidated       Assets:   (In thousands) Cash and cash equivalents $   1,010,275 $   5,658 $   178,079 $   –   $   1,194,012 Reinsurance recoverables and trade receivables, net   118,741   67,069   38,616   –     224,426 Inventories and parts, net   105,577   –   –   –     105,577 Prepaid expenses   469,144   –   –   –     469,144 Investments, fixed maturities and marketable equities   –   295,753   2,399,903   –     2,695,656 Investments, other   20,733   90,412   378,614   –     489,759 Deferred policy acquisition costs, net   –   –   89,749   –     89,749 Other assets   44,763   436   2,531   –     47,730 Right of use assets - financing, net   877,038   –   –   –     877,038 Right of use assets - operating, net   92,245   92   168   –     92,505 Related party assets   54,042   6,854   13,850   (39,351) (c)   35,395     2,792,558   466,274   3,101,510   (39,351)     6,320,991                         Investment in subsidiaries   741,860   –   –   (741,860) (b)   –                         Property, plant and equipment, at cost:                       Land   1,075,813   –   –   –     1,075,813 Buildings and improvements   5,163,705   –   –   –     5,163,705 Furniture and equipment   786,505   –   –   –     786,505 Rental trailers and other rental equipment   477,921   –   –   –     477,921 Rental trucks   3,909,724   –   –   –     3,909,724     11,413,668   –   –   –     11,413,668 Less:   Accumulated depreciation   (3,083,053)   –   –   –     (3,083,053) Total property, plant and equipment, net   8,330,615   –   –   –     8,330,615 Total assets $   11,865,033 $   466,274 $   3,101,510 $   (781,211)   $   14,651,606                         (a) Balances as of December 31, 2020                       (b) Eliminate investment in subsidiaries                       (c) Eliminate intercompany receivables and payables                         Consolidating balance sheets by industry segment as of March 31, 2021, continued       Moving & Storage   Property & Casualty Insurance (a)   Life   Eliminations     AMERCO                             (In thousands) Liabilities:                       Accounts payable and accrued expenses $ 636,257 $ 2,029 $ 7,289 $ –   $ 645,575 Notes, loans and finance leases payable, net   4,657,720   –   11,187   –     4,668,907 Operating lease liability   92,236   96   178   –     92,510 Policy benefits and losses, claims and loss expenses payable   427,073   178,942   391,686   –     997,701 Liabilities from investment contracts   –   –   2,161,530   –     2,161,530 Other policyholders' funds and liabilities   –   3,698   8,722   –     12,420 Deferred income   42,592   –   –   –     42,592 Deferred income taxes, net   1,136,149   13,046   29,294   –     1,178,489 Related party liabilities   25,413   5,821   12,406   (43,640) (c)   – Total liabilities   7,017,440   203,632   2,622,292   (43,640)     9,799,724                         Stockholders' equity:                       Series preferred stock:                       Series A preferred stock   –   –   –   –     – Series B preferred stock   –   –   –   –     – Series A common stock   –   –   –   –     – Common stock   10,497   3,301   2,500   (5,801) (b)   10,497 Additional paid-in capital   454,029   91,120   26,271   (117,601) (b)   453,819 Accumulated other comprehensive income (loss)   102,568   22,546   140,817   (159,074) (b)   106,857 Retained earnings   4,958,149   145,675   309,630   (455,095) (b)   4,958,359 Cost of common stock in treasury, net   (525,653)   –   –   –     (525,653) Cost of preferred stock in treasury, net   (151,997)   –   –   –     (151,997) Total stockholders' equity   4,847,593   262,642   479,218   (737,571)     4,851,882 Total liabilities and stockholders' equity $ 11,865,033 $ 466,274 $ 3,101,510 $ (781,211)   $ 14,651,606                         (a) Balances as of December 31, 2020                       (b) Eliminate investment in subsidiaries                       (c) Eliminate intercompany receivables and payables
Consolidated Statement of Operations by Industry Segment	Consolidating statement of operations by industry segment for the quarter ended June 30, 2021 are as follows:       Moving & Storage   Property & Casualty Insurance (a)   Life   Eliminations     AMERCO     (Unaudited)     (In thousands) Revenues:                       Self-moving equipment rentals $ 1,036,213 $ – $ – $ (836) (c) $ 1,035,377 Self-storage revenues   137,393   –   –   –     137,393 Self-moving and self-storage products and service sales   104,885   –   –   –     104,885 Property management fees   8,449   –   –   –     8,449 Life insurance premiums   –   –   28,705   –     28,705 Property and casualty insurance premiums   –   17,443   –   (574) (c)   16,869 Net investment and interest income   680   6,013   29,324   (1,018) (b)   34,999 Other revenue   105,634   –   630   (85) (b)   106,179 Total revenues   1,393,254   23,456   58,659   (2,513)     1,472,856                         Costs and expenses:                       Operating expenses   601,831   8,813   5,375   (1,490) (b,c)   614,529 Commission expenses   113,149   –   –   –     113,149 Cost of sales   69,915   –   –   –     69,915 Benefits and losses   –   5,227   42,071   –     47,298 Amortization of deferred policy acquisition costs   –   –   8,823   –     8,823 Lease expense   8,077   184   24   (638) (b)   7,647 Depreciation, net of gains on disposals   121,717   –   –   –     121,717 Net gains on disposal of real estate   (4,430)   –   –   –     (4,430) Total costs and expenses   910,259   14,224   56,293   (2,128)     978,648                         Earnings from operations before equity in earnings of subsidiaries   482,995   9,232   2,366   (385)     494,208                         Equity in earnings of subsidiaries   9,119   –   –   (9,119) (d)   –                         Earnings from operations   492,114   9,232   2,366   (9,504)     494,208 Other components of net periodic benefit costs   (280)   –   –   –     (280) Interest expense   (39,443)   –   (120)   385 (b)   (39,178) Pretax earnings   452,391   9,232   2,246   (9,119)     454,750 Income tax expense   (107,216)   (1,930)   (429)   –     (109,575) Earnings available to common stockholders $ 345,175 $ 7,302 $ 1,817 $ (9,119)   $ 345,175                         (a) Balances for the quarter ended March 31, 2021                       (b) Eliminate intercompany lease / interest income                       (c) Eliminate intercompany premiums                       (d) Eliminate equity in earnings of subsidiaries	Consolidating statements of operations by industry for the quarter ended June 30, 2020 are as follows:       Moving & Storage   Property & Casualty Insurance (a)   Life   Eliminations     AMERCO     (Unaudited)     (In thousands) Revenues:                       Self-moving equipment rentals $ 654,913 $ – $ – $ (628) (c) $ 654,285 Self-storage revenues   108,955   –   –   –     108,955 Self-moving and self-storage products and service sales   91,350   –   –   –     91,350 Property management fees   7,347   –   –   –     7,347 Life insurance premiums   –   –   30,908   –     30,908 Property and casualty insurance premiums   –   14,507   –   (773) (c)   13,734 Net investment and interest income   662   (873)   18,006   (813) (b)   16,982 Other revenue   63,073   –   739   (136) (b)   63,676 Total revenues   926,300   13,634   49,653   (2,350)     987,237                         Costs and expenses:                       Operating expenses   480,081   8,825   5,288   (1,532) (b,c)   492,662 Commission expenses   69,175   –   –   –     69,175 Cost of sales   52,831   –   –   –     52,831 Benefits and losses   –   4,030   35,547   –     39,577 Amortization of deferred policy acquisition costs   –   –   6,888   –     6,888 Lease expense   7,137   1   10   (545) (b)   6,603 Depreciation, net of gains on disposals   165,671   –   –   –     165,671 Net gains on disposal of real estate   (256)   –   –   –     (256) Total costs and expenses   774,639   12,856   47,733   (2,077)     833,151                         Earnings from operations before equity in earnings of subsidiaries   151,661   778   1,920   (273)     154,086                         Equity in earnings of subsidiaries   2,395   –   –   (2,395) (d)   –                         Earnings from operations   154,056   778   1,920   (2,668)     154,086 Other components of net periodic benefit costs   (247)   –   –   –     (247) Interest expense   (39,794)   –   –   273 (b)   (39,521) Pretax earnings   114,015   778   1,920   (2,395)     114,318 Income tax expense   (26,289)   (162)   (141)   –     (26,592) Earnings available to common stockholders $ 87,726 $ 616 $ 1,779 $ (2,395)   $ 87,726                         (a) Balances for the quarter ended March 31, 2020                       (b) Eliminate intercompany lease / interest income                       (c) Eliminate intercompany premiums                       (d) Eliminate equity in earnings of subsidiaries
Consolidated Cash Flow Statement by Industry Segment	Consolidating cash flow statements by industry segment for the quarter ended June 30, 2021 are as follows:       Moving & Storage Consolidated   Property & Casualty Insurance (a)   Life Insurance (a)   Elimination     AMERCO Consolidated     (Unaudited) Cash flows from operating activities:   (In thousands) Net earnings $   345,175 $   7,302 $   1,817 $   (9,119)   $   345,175 Earnings from consolidated entities   (9,119)   –   –   9,119     – Adjustments to reconcile net earnings to the cash provided by operations:                       Depreciation   172,040   –   –   –     172,040 Amortization of deferred policy acquisition costs   –   –   8,823   –     8,823 Amortization of premiums and accretion of discounts related to investments, net   –   413   3,948   –     4,361 Amortization of debt issuance costs   1,332   –   –   –     1,332 Interest credited to policyholders   –   –   15,583   –     15,583 Change in allowance for losses on trade receivables   (478)   (5)   (1)   –     (484) Change in allowance for inventories and parts reserve   3,403   –   –   –     3,403 Net gains on disposal of personal property   (50,323)   –   –   –     (50,323) Net gains on disposal of real estate   (4,430)   –   –   –     (4,430) Net gains on sales of investments   –   (37)   (2,432)   –     (2,469) Net gains on equity investments   –   (2,231)   –   –     (2,231) Deferred income taxes   81,341   604   429   –     82,374 Net change in other operating assets and liabilities:                       Reinsurance recoverables and trade receivables   (1,658)   (520)   (5,904)   –     (8,082) Inventories and parts   (15,765)   –   –   –     (15,765) Prepaid expenses   162,706   –   –   –     162,706 Capitalization of deferred policy acquisition costs   –   –   (8,990)   –     (8,990) Other assets   (436)   (323)   (94)   –     (853) Related party assets   302   260   –   –     562 Accounts payable and accrued expenses   60,902   225   10,472   –     71,599 Policy benefits and losses, claims and loss expenses payable   5,942   352   2,770   –     9,064 Other policyholders' funds and liabilities   –   (461)   (969)   –     (1,430) Deferred income   12,125   –   (262)   –     11,863 Related party liabilities   1,422   (1,972)   935   –     385 Net cash provided by operating activities   764,481   3,607   26,125   –     794,213                         Cash flows from investing activities:                       Escrow deposits   1,887   –   –   –     1,887 Purchases of:                       Property, plant and equipment   (508,411)   –   –   –     (508,411) Short term investments   –   (11,680)   (130)   –     (11,810) Fixed maturities investments   –   (7,466)   (274,041)   –     (281,507) Preferred stock   –   –   (8,000)   –     (8,000) Real estate   –   –   (67)   –     (67) Mortgage loans   –   (4,850)   (37,688)   –     (42,538) Proceeds from sales and paydowns of:                       Property, plant and equipment   182,146   –   –   –     182,146 Short term investments   –   12,558   –   –     12,558 Fixed maturities investments   –   5,136   121,820   –     126,956 Mortgage loans   –   283   5,345   –     5,628 Net cash used by investing activities   (324,378)   (6,019)   (192,761)   –     (523,158)     (page 1 of 2) (a) Balance for the period ended March 31, 2021                         Consolidating cash flow statements by industry segment for the quarter ended June 30, 2021, continued       Moving & Storage   Property &   Life   Elimination     AMERCO     (Unaudited) Cash flows from financing activities:   (In thousands) Borrowings from credit facilities   161,854   –   –   –     161,854 Principal repayments on credit facilities   (109,206)   –   (128)   –     (109,334) Payments of debt issuance costs   (352)   –   –   –     (352) Finance lease payments   (45,170)   –   –   –     (45,170) Investment contract deposits   –   –   113,779   –     113,779 Investment contract withdrawals   –   –   (64,332)   –     (64,332) Net cash provided by financing activities   7,126   –   49,319   –     56,445                         Effects of exchange rate on cash   (1,531)   –   –   –     (1,531)                         Increase (decrease) in cash and cash equivalents   445,698   (2,412)   (117,317)   –     325,969 Cash and cash equivalents at beginning of period   1,010,275   5,658   178,079   –     1,194,012 Cash and cash equivalents at end of period $   1,455,973 $   3,246 $   60,762 $   –   $   1,519,981     (page 2 of 2) (a) Balance for the period ended March 31, 2021	Consolidating cash flow statements by industry segment for the quarter ended June 30, 2020 are as follows:       Moving & Storage Consolidated   Property & Casualty Insurance (a)   Life Insurance (a)   Elimination     AMERCO Consolidated     (Unaudited) Cash flows from operating activities:   (In thousands) Net earnings $   87,726 $   616 $   1,779 $   (2,395)   $   87,726 Earnings from consolidated entities   (2,395)   –   –   2,395     – Adjustments to reconcile net earnings to cash provided by operations:                       Depreciation   166,740   –   –   –     166,740 Amortization of deferred policy acquisition costs   –   –   6,888   –     6,888 Amortization of premiums and accretion of discounts related to investments, net   –   395   3,155   –     3,550 Amortization of debt issuance costs   1,297   –   –   –     1,297 Interest credited to policyholders   –   –   7,667   –     7,667 Change in allowance for losses on trade receivables   60   –   –   –     60 Change in allowance for inventories and parts reserve   (99)   –   –   –     (99) Net gains on disposal of personal property   (1,069)   –   –   –     (1,069) Net gains on disposal of real estate   (256)   –   –   –     (256) Net gains (losses) on sales of investments   –   (13)   2,027   –     2,014 Net losses on equity investments   –   3,989   –   –     3,989 Deferred income taxes   28,939   1,070   (2,475)   –     27,534 Net change in other operating assets and liabilities:                       Reinsurance recoverables and trade receivables   (24,749)   5,725   (4,570)   –     (23,594) Inventories and parts   350   –   –   –     350 Prepaid expenses   (22,831)   –   –   –     (22,831) Capitalization of deferred policy acquisition costs   –   –   (7,308)   –     (7,308) Other assets   758   (340)   (344)   –     74 Related party assets   7,302   27   –   –     7,329 Accounts payable and accrued expenses   56,522   (246)   1,997   –     58,273 Policy benefits and losses, claims and loss expenses payable   294   (2,769)   3,003   –     528 Other policyholders' funds and liabilities   –   (4,089)   663   –     (3,426) Deferred income   11,238   –   3,660   –     14,898 Related party liabilities   1,867   (834)   (1,282)   –     (249) Net cash provided by operating activities   311,694   3,531   14,860   –     330,085                         Cash flows from investing activities:                       Escrow deposits   1,401   –   –   –     1,401 Purchases of:                       Property, plant and equipment   (249,740)   –   –   –     (249,740) Short term investments   –   (8,989)   (636)   –     (9,625) Fixed maturities investments   –   (1,864)   (92,329)   –     (94,193) Real estate   –   –   (192)   –     (192) Mortgage loans   –   –   (33,300)   –     (33,300) Proceeds from sales and paydowns of:                       Property, plant and equipment   76,412   –   –   –     76,412 Short term investments   –   1,980   468   –     2,448 Fixed maturities investments   –   4,402   105,763   –     110,165 Mortgage loans   –   265   1,167   –     1,432 Net cash used by investing activities   (171,927)   (4,206)   (19,059)   –     (195,192)     (page 1 of 2) (a) Balance for the period ended March 31, 2020                         Consolidating cash flow statements by industry segment for the quarter ended June 30, 2020, continued       Moving & Storage   Property &   Life   Elimination     AMERCO     (Unaudited) Cash flows from financing activities:   (In thousands) Borrowings from credit facilities   367,451   –   9,600   –     377,051 Principal repayments on credit facilities   (144,489)   –   (9,600)   –     (154,089) Payment of debt issuance costs   (1,677)   –   –   –     (1,677) Finance lease payments   (68,554)   –   –   –     (68,554) Net contribution from (to) related party   18,599   –   –   –     18,599 Investment contract deposits   –   –   75,366   –     75,366 Investment contract withdrawals   –   –   (51,633)   –     (51,633) Net cash provided by financing activities   171,330   –   23,733   –     195,063                         Effects of exchange rate on cash   766   –   –   –     766                         Increase (decrease) in cash and cash equivalents   311,863   (675)   19,534   –     330,722 Cash and cash equivalents at beginning of period   459,078   4,794   30,480   –     494,352 Cash and cash equivalents at end of period $   770,941 $   4,119 $   50,014 $   –   $   825,074     (page 2 of 2) (a) Balance for the period ended March 31, 2020