Consolidating financial information by industry segment (Cash Flow Statements) (Details) - USD ($) $ in Thousands	12 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Mar. 31, 2020
Cash flow from operating activities:
Net earnings	$ 1,123,286	$ 610,856	$ 442,048
Earnings from consolidated subsidiaries	0	0	0
Adjustments to reconcile net earnings to cash provided by operations:
Depreciation	696,955	664,001	664,120
Amortization of deferred policy acquisition costs	33,854	28,293	31,219
Amortization of premiums and accretion of discounts related to investments, inc	19,749	14,229	13,317
Amortization of debt issuance costs	5,659	5,948	4,426
Interest credited to policyholders	64,692	55,321	51,857
Change in allowance for losses on trade receivables	4,227	1,206	(14)
Change in allowance for inventory reserves	15,235	1,298	640
Net gains on disposal of personal property	(214,203)	(54,071)	(27,057)
Net gains on disposal of real estate	(4,120)	3,281	(758)
Net gains on sales of investments	(11,872)	(10,058)	(13,596)
Net (gains) losses on equity investments	(7,837)	(394)	(3,783)
Deferred income taxes	101,091	68,411	317,893
Net change in other operating assets and liabilities:
Reinsurance recoverables and trade receivables	(9,187)	(39,516)	38,129
Inventories and parts	(68,536)	(5,775)	1,776
Prepaid expenses	232,342	94,359	(391,120)
Capitalization of deferred policy acquisition costs	(32,626)	(36,162)	(24,447)
Other assets	(2,706)	29,865	(1,295)
Related party assets	(10,357)	(487)	(5,645)
Accounts payable and accrued expenses	28,752	92,925	(4,530)
Policy benefits and losses, claims and loss expenses payable	(19,692)	(1,992)	(12,618)
Other policyholders' funds and liabilities	(1,608)	2,230	(4,857)
Deferred income	5,216	11,567	(1,818)
Related party liabilities	(2,079)	60	1,626
Net cash provided by operating activities	1,946,235	1,535,395	1,075,513
Cash flow from investing activities:
Escrow deposits	(9,328)	(5,221)	6,617
Purchase of:
Property, plant and equipment	(2,136,537)	(1,441,475)	(2,309,406)
Short term investments	(74,418)	(69,929)	(61,226)
Fixed maturities investments	(627,326)	(606,233)	(379,349)
Equity securities	(19,299)	(962)	(83)
Preferred stock	(8,000)	(16,144)	0
Real estate	(261)	(622)	(4,286)
Mortgage loans	(158,147)	(158,071)	(62,016)
Proceeds from sale and paydowns of:
Property, plant and equipment	623,235	537,484	687,375
Short term investments	51,591	69,718	59,056
Fixed maturities investments	360,937	529,239	268,636
Equity securities	2,046	207	185
Preferred stock	2,000	2,700	2,375
Real estate	113	255	311
Mortgage loans	126,218	29,525	25,162
Net cash used by investing activities	(1,867,176)	(1,129,529)	(1,766,649)
Cash flow from financing activities:
Borrowings from credit facilities	1,969,474	922,008	1,121,412
Principal repayments on credit facilities	(437,506)	(662,588)	(349,986)
Debt issuance costs	(13,156)	(5,793)	(5,332)
Capital lease payments	(166,262)	(221,247)	(307,782)
Employee stock ownership plan value	0	0	(206)
Common stock dividends paid	(29,412)	(49,019)	(29,404)
Net contribution from (to) related party		0	0
Investment contract deposits	347,520	517,856	234,640
Investment contract withdrawals	(237,503)	(213,864)	(151,022)
Net cash provided by financing activities	1,433,155	287,353	512,320
Effects of exchange rate on cash	(2,089)	6,441	(533)
Increase (decrease) cash and cash equivalents	1,510,125	699,660	(179,349)
Cash and cash equivalents at the beginning of period	1,194,012	494,352	673,701
Cash and cash equivalents at the end of the period	2,704,137	1,194,012	494,352
Operating Segments [Member] | Moving and Storage Consolidations [Member]
Cash flow from operating activities:
Net earnings	1,123,286	610,856	442,048
Earnings from consolidated subsidiaries	(54,746)	(44,441)	(55,789)
Adjustments to reconcile net earnings to cash provided by operations:
Depreciation	696,955	664,001	664,120
Amortization of deferred policy acquisition costs	0	0	0
Amortization of premiums and accretion of discounts related to investments, inc	0	0	0
Amortization of debt issuance costs	5,659	5,948	4,426
Interest credited to policyholders	0	0	0
Change in allowance for losses on trade receivables	4,689	1,424	(14)
Change in allowance for inventory reserves	15,235	1,298	640
Net gains on disposal of personal property	(214,203)	(54,071)	(27,057)
Net gains on disposal of real estate	(4,120)	3,281	(758)
Net gains on sales of investments	0	0	0
Net (gains) losses on equity investments	0	0	0
Deferred income taxes	106,869	72,407	323,980
Net change in other operating assets and liabilities:
Reinsurance recoverables and trade receivables	(28,776)	(60,806)	30,771
Inventories and parts	(68,536)	(5,775)	1,776
Prepaid expenses	232,342	94,359	(391,120)
Capitalization of deferred policy acquisition costs	0	0	0
Other assets	(2,919)	29,879	(3,099)
Related party assets	(10,517)	(12,790)	(5,106)
Accounts payable and accrued expenses	23,839	96,309	(4,428)
Policy benefits and losses, claims and loss expenses payable	(8,428)	14,919	3,092
Other policyholders' funds and liabilities	0	0	0
Deferred income	6,368	10,959	(1,818)
Related party liabilities	255	1,136	(1,170)
Net cash provided by operating activities	1,823,252	1,428,893	980,494
Cash flow from investing activities:
Escrow deposits	(9,328)	(5,221)	6,617
Purchase of:
Property, plant and equipment	(2,136,537)	(1,441,475)	(2,309,406)
Short term investments	0	0	0
Fixed maturities investments	0	0	0
Equity securities	0	0	0
Preferred stock	0	0
Real estate	(33)	0	0
Mortgage loans	0	0	0
Proceeds from sale and paydowns of:
Property, plant and equipment	623,235	537,484	687,375
Short term investments	0	0	0
Fixed maturities investments	0	0	0
Equity securities	0	0	0
Preferred stock	0	0	0
Real estate	113	255	311
Mortgage loans	0	0	0
Net cash used by investing activities	(1,522,550)	(908,957)	(1,615,103)
Cash flow from financing activities:
Borrowings from credit facilities	1,969,474	912,408	1,118,912
Principal repayments on credit facilities	(426,319)	(652,728)	(347,486)
Debt issuance costs	(13,156)	(5,793)	(5,332)
Capital lease payments	(166,262)	(221,247)	(307,782)
Employee stock ownership plan value			(206)
Common stock dividends paid	(29,412)	(49,019)	(29,404)
Net contribution from (to) related party		41,199	21,600
Investment contract deposits	0	0	0
Investment contract withdrawals	0	0	0
Net cash provided by financing activities	1,334,325	24,820	450,302
Effects of exchange rate on cash	(2,089)	6,441	(533)
Increase (decrease) cash and cash equivalents	1,632,938	551,197	(184,840)
Cash and cash equivalents at the beginning of period	1,010,275	459,078	643,918
Cash and cash equivalents at the end of the period	2,643,213	1,010,275	459,078
Operating Segments [Member] | Property and Casualty Insurance [Member]
Cash flow from operating activities:
Net earnings	39,402	25,720	33,928
Earnings from consolidated subsidiaries	0	0	0
Adjustments to reconcile net earnings to cash provided by operations:
Depreciation	0	0	0
Amortization of deferred policy acquisition costs	0	0	0
Amortization of premiums and accretion of discounts related to investments, inc	1,638	1,578	1,469
Amortization of debt issuance costs	0	0	0
Interest credited to policyholders	0	0	0
Change in allowance for losses on trade receivables	(456)	(217)	0
Change in allowance for inventory reserves	0	0	0
Net gains on disposal of personal property	0	0	0
Net gains on disposal of real estate	0	0	0
Net gains on sales of investments	(991)	(158)	(355)
Net (gains) losses on equity investments	(7,837)	(394)	(3,783)
Deferred income taxes	1,347	459	(2,847)
Net change in other operating assets and liabilities:
Reinsurance recoverables and trade receivables	17,180	27,302	8,127
Inventories and parts	0	0	0
Prepaid expenses	0	0	0
Capitalization of deferred policy acquisition costs	0	0	0
Other assets	346	537	2,098
Related party assets	160	303	(539)
Accounts payable and accrued expenses	1,821	(3,497)	2,688
Policy benefits and losses, claims and loss expenses payable	(18,563)	(31,398)	(19,618)
Other policyholders' funds and liabilities	(177)	(2,053)	491
Deferred income	0	0	0
Related party liabilities	(2,644)	1,187	819
Net cash provided by operating activities	31,226	19,369	22,478
Cash flow from investing activities:
Escrow deposits	0	0	0
Purchase of:
Property, plant and equipment	0	0	0
Short term investments	(74,418)	(69,929)	(60,590)
Fixed maturities investments	(10,248)	(18,823)	(13,001)
Equity securities	(17,919)	0	0
Preferred stock	0	0
Real estate	(59)	0	(328)
Mortgage loans	(24,032)	(18,035)	(18,050)
Proceeds from sale and paydowns of:
Property, plant and equipment	0	0	0
Short term investments	50,737	69,669	59,056
Fixed maturities investments	24,201	20,854	25,386
Equity securities	20	0	185
Preferred stock	2,000	2,700	1,375
Real estate	0	0	0
Mortgage loans	23,634	17,659	4,126
Net cash used by investing activities	(26,084)	4,095	(1,841)
Cash flow from financing activities:
Borrowings from credit facilities	0	0	0
Principal repayments on credit facilities	0	0	0
Debt issuance costs	0	0	0
Capital lease payments	0	0	0
Employee stock ownership plan value			0
Common stock dividends paid	0	0	0
Net contribution from (to) related party		(22,600)	(21,600)
Investment contract deposits	0	0	0
Investment contract withdrawals	0	0	0
Net cash provided by financing activities	0	(22,600)	(21,600)
Effects of exchange rate on cash	0	0	0
Increase (decrease) cash and cash equivalents	5,142	864	(963)
Cash and cash equivalents at the beginning of period	5,658	4,794	5,757
Cash and cash equivalents at the end of the period	10,800	5,658	4,794
Operating Segments [Member] | Life Insurance [Member]
Cash flow from operating activities:
Net earnings	15,344	18,721	21,861
Earnings from consolidated subsidiaries	0	0	0
Adjustments to reconcile net earnings to cash provided by operations:
Depreciation	0	0	0
Amortization of deferred policy acquisition costs	33,854	28,293	31,219
Amortization of premiums and accretion of discounts related to investments, inc	18,111	12,651	11,848
Amortization of debt issuance costs	0	0	0
Interest credited to policyholders	64,692	55,321	51,857
Change in allowance for losses on trade receivables	(6)	(1)	0
Change in allowance for inventory reserves	0	0	0
Net gains on disposal of personal property	0	0	0
Net gains on disposal of real estate	0	0	0
Net gains on sales of investments	(10,881)	(9,900)	(13,241)
Net (gains) losses on equity investments	0	0	0
Deferred income taxes	(7,125)	(4,455)	(3,240)
Net change in other operating assets and liabilities:
Reinsurance recoverables and trade receivables	2,409	(6,012)	(769)
Inventories and parts	0	0	0
Prepaid expenses	0	0	0
Capitalization of deferred policy acquisition costs	(32,626)	(36,162)	(24,447)
Other assets	(133)	(551)	(294)
Related party assets	0	0	0
Accounts payable and accrued expenses	3,092	113	(2,790)
Policy benefits and losses, claims and loss expenses payable	7,299	14,487	3,908
Other policyholders' funds and liabilities	(1,431)	4,283	(5,348)
Deferred income	(1,152)	608	0
Related party liabilities	310	9,737	1,977
Net cash provided by operating activities	91,757	87,133	72,541
Cash flow from investing activities:
Escrow deposits	0	0	0
Purchase of:
Property, plant and equipment	0	0	0
Short term investments	0	0	(636)
Fixed maturities investments	(617,078)	(587,410)	(366,348)
Equity securities	(1,380)	(962)	(83)
Preferred stock	(8,000)	(16,144)
Real estate	(169)	(622)	(3,958)
Mortgage loans	(134,115)	(140,036)	(43,966)
Proceeds from sale and paydowns of:
Property, plant and equipment	0	0	0
Short term investments	854	49	0
Fixed maturities investments	336,736	508,385	243,250
Equity securities	2,026	207	0
Preferred stock	0	0	1,000
Real estate	0	0	0
Mortgage loans	102,584	11,866	21,036
Net cash used by investing activities	(318,542)	(224,667)	(149,705)
Cash flow from financing activities:
Borrowings from credit facilities	0	9,600	2,500
Principal repayments on credit facilities	(11,187)	(9,860)	(2,500)
Debt issuance costs	0	0	0
Capital lease payments	0	0	0
Employee stock ownership plan value			0
Common stock dividends paid	0	0	0
Net contribution from (to) related party		(18,599)	0
Investment contract deposits	347,520	517,856	234,640
Investment contract withdrawals	(237,503)	(213,864)	(151,022)
Net cash provided by financing activities	98,830	285,133	83,618
Effects of exchange rate on cash	0	0	0
Increase (decrease) cash and cash equivalents	(127,955)	147,599	6,454
Cash and cash equivalents at the beginning of period	178,079	30,480	24,026
Cash and cash equivalents at the end of the period	50,124	178,079	30,480
Eliminations [Member]
Cash flow from operating activities:
Net earnings	(54,746)	(44,441)	(55,789)
Earnings from consolidated subsidiaries	54,746	44,441	55,789
Adjustments to reconcile net earnings to cash provided by operations:
Depreciation	0	0	0
Amortization of deferred policy acquisition costs	0	0	0
Amortization of premiums and accretion of discounts related to investments, inc	0	0	0
Amortization of debt issuance costs	0	0	0
Interest credited to policyholders	0	0	0
Change in allowance for losses on trade receivables	0	0	0
Change in allowance for inventory reserves	0	0	0
Net gains on disposal of personal property	0	0	0
Net gains on disposal of real estate	0	0	0
Net gains on sales of investments	0	0	0
Net (gains) losses on equity investments	0	0	0
Deferred income taxes	0	0	0
Net change in other operating assets and liabilities:
Reinsurance recoverables and trade receivables	0	0	0
Inventories and parts	0	0	0
Prepaid expenses	0	0	0
Capitalization of deferred policy acquisition costs	0	0	0
Other assets	0	0	0
Related party assets	0	12,000	0
Accounts payable and accrued expenses	0	0	0
Policy benefits and losses, claims and loss expenses payable	0	0	0
Other policyholders' funds and liabilities	0	0	0
Deferred income	0	0	0
Related party liabilities	0	(12,000)	0
Net cash provided by operating activities	0	0	0
Cash flow from investing activities:
Escrow deposits	0	0	0
Purchase of:
Property, plant and equipment	0	0	0
Short term investments	0	0	0
Fixed maturities investments	0	0	0
Equity securities	0	0	0
Preferred stock	0	0
Real estate	0	0	0
Mortgage loans	0	0	0
Proceeds from sale and paydowns of:
Property, plant and equipment	0	0	0
Short term investments	0	0	0
Fixed maturities investments	0	0	0
Equity securities	0	0	0
Preferred stock	0	0	0
Real estate	0	0	0
Mortgage loans	0	0	0
Net cash used by investing activities	0	0	0
Cash flow from financing activities:
Borrowings from credit facilities	0	0	0
Principal repayments on credit facilities	0	0	0
Debt issuance costs	0	0	0
Capital lease payments	0	0	0
Employee stock ownership plan value			0
Common stock dividends paid	0	0	0
Net contribution from (to) related party		0	0
Investment contract deposits	0	0	0
Investment contract withdrawals	0	0	0
Net cash provided by financing activities	0	0	0
Effects of exchange rate on cash	0	0	0
Increase (decrease) cash and cash equivalents	0	0	0
Cash and cash equivalents at the beginning of period	0	0	0
Cash and cash equivalents at the end of the period	$ 0	$ 0	$ 0