Consolidating financial information by industry segment (Cash Flow Statements) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2022	Dec. 31, 2021
Cash flow from operating activities:
Net earnings	$ 199,244	$ 281,466	$ 885,261	$ 1,036,539
Earnings from consolidated entities			0	0
Adjustments to reconcile net earnings to cash provided by operations:
Depreciation			544,176	519,181
Amortization of deferred policy acquisition costs	6,979	7,947	21,623	23,520
Amortization of premiums and accretion of discounts related to investments, inc			15,232	14,486
Amortization of debt issuance costs			5,694	4,200
Interest credited to policyholders			39,048	47,181
Change in allowance for losses on trade receivables			(4,617)	1,243
Change in allowance for inventory reserves			6,991	9,799
Net gain on sale of real and personal property			(199,196)	(157,980)
Net losses on disposal of real estate	859	977	5,038	(2,930)
Net (gain) loss on sale of investments			8,695	(3,495)
Net losses on equity investments			10,906	(3,695)
Deferred income tax			121,707	130,760
Net change in other operating assets and liabilities:
Reinsurance recoverables and trade receivables			25,853	(7,371)
Inventories			1,682	(70,796)
Prepaid expenses			7,867	257,591
Capitalization of deferred policy acquisition costs			(20,406)	(25,703)
Other assets			2,683	1,178
Related party assets			(26,775)	(18,683)
Accounts payable and accrued expenses			62,430	33,258
Policy benefits and losses, claims and loss expenses payable			3,490	6,411
Other policyholders' funds and liabilities			1,767	(2,810)
Deferred income			(2,168)	(526)
Related party liabilities			(1,301)	(2,207)
Net cash provided by operating activities			1,515,680	1,789,151
Cash flow from investing activities:
Escrow deposits			159	5,695
Purchase of:
Property, plant and equipment			(2,076,424)	(1,652,984)
Short term investments			(49,801)	(31,074)
Fixed maturity investments			(491,431)	(448,283)
Equity securities			(4,828)	(1,380)
Preferred stock			0	(8,000)
Real estate			(7,854)	(190)
Mortgage loans			(148,017)	(131,633)
Proceeds from sale of:
Property, plant and equipment			533,595	483,783
Short term investments			67,062	20,669
Fixed maturity investments			148,290	284,347
Equity securities			1,187	2,026
Preferred stock			0	2,000
Real estate			0
Mortgage loans			156,292	28,064
Net cash used by investing activities			(1,871,770)	(1,446,960)
Cash flow from financing activities:
Borrowings from credit facilities			975,966	1,202,412
Principal repayments on credit facilities			(695,321)	(333,419)
Payment of debt issuance costs			(4,962)	(8,006)
Capital lease payments			(95,290)	(129,150)
Securitization deposits			137	0
Voting Common Stock dividends paid			(19,608)	(29,412)
Series N Non-Voting Common Stock dividends	(7,059)		(7,059)	0
Investment contract deposits			258,157	271,657
Investment contract withdrawals			(236,742)	(177,777)
Net cash provided by (used in) financing activities			175,278	796,305
Effects of exchange rate on cash			(12,706)	(5,046)
Increase (decrease) in cash and cash equivalents			(193,518)	1,133,450
Cash and cash equivalents at beginning of period			2,704,137	1,194,012
Cash and cash equivalents at the end of period	2,510,619	2,327,462	2,510,619	2,327,462
Property and Casualty Insurance [Member]
Cash flow from financing activities:
Effects of exchange rate on cash				0
Increase (decrease) in cash and cash equivalents				2,407
Cash and cash equivalents at beginning of period				5,658
Cash and cash equivalents at the end of period		8,065		8,065
Life Insurance [Member]
Cash flow from financing activities:
Effects of exchange rate on cash				0
Increase (decrease) in cash and cash equivalents				(112,897)
Cash and cash equivalents at beginning of period				178,079
Cash and cash equivalents at the end of period		65,182		65,182
Operating Segments [Member] | Moving and Storage Consolidations [Member]
Cash flow from operating activities:
Net earnings	199,244	281,466	885,261	1,036,539
Earnings from consolidated entities			(26,420)	(37,811)
Adjustments to reconcile net earnings to cash provided by operations:
Depreciation			544,176	519,181
Amortization of deferred policy acquisition costs	0	0	0	0
Amortization of premiums and accretion of discounts related to investments, inc			0	0
Amortization of debt issuance costs			5,694	4,200
Interest credited to policyholders			0	0
Change in allowance for losses on trade receivables			(4,470)	1,413
Change in allowance for inventory reserves			6,991	9,799
Net gain on sale of real and personal property			(199,196)	(157,980)
Net losses on disposal of real estate	859	977	5,038	(2,930)
Net (gain) loss on sale of investments			0	0
Net losses on equity investments			0	0
Deferred income tax			125,717	134,541
Net change in other operating assets and liabilities:
Reinsurance recoverables and trade receivables			23,092	(10,403)
Inventories			1,682	(70,796)
Prepaid expenses			7,867	257,591
Capitalization of deferred policy acquisition costs			0	0
Other assets			3,291	1,213
Related party assets			(29,478)	(17,870)
Accounts payable and accrued expenses			61,253	30,634
Policy benefits and losses, claims and loss expenses payable			13,299	1,172
Other policyholders' funds and liabilities			0	0
Deferred income			(4,013)	687
Related party liabilities			(799)	(267)
Net cash provided by operating activities			1,418,985	1,698,913
Cash flow from investing activities:
Escrow deposits			159	5,695
Purchase of:
Property, plant and equipment			(2,079,490)	(1,652,984)
Short term investments			0	0
Fixed maturity investments			(224,999)	0
Equity securities			0	0
Preferred stock			0	0
Real estate			(2,677)	(33)
Mortgage loans			0	0
Proceeds from sale of:
Property, plant and equipment			533,595	483,783
Short term investments			0	0
Fixed maturity investments			0	0
Equity securities			0	0
Preferred stock				0
Real estate			0
Mortgage loans			0	0
Net cash used by investing activities			(1,773,412)	(1,163,539)
Cash flow from financing activities:
Borrowings from credit facilities			975,966	1,202,412
Principal repayments on credit facilities			(695,321)	(322,232)
Payment of debt issuance costs			(4,962)	(8,006)
Capital lease payments			(95,290)	(129,150)
Securitization deposits			137
Voting Common Stock dividends paid			(19,608)	(29,412)
Series N Non-Voting Common Stock dividends			(7,059)
Investment contract deposits			0	0
Investment contract withdrawals			0	0
Net cash provided by (used in) financing activities			153,863	713,612
Effects of exchange rate on cash			(12,706)	(5,046)
Increase (decrease) in cash and cash equivalents			(213,270)	1,243,940
Cash and cash equivalents at beginning of period			2,643,213	1,010,275
Cash and cash equivalents at the end of period	2,429,943	2,254,215	2,429,943	2,254,215
Operating Segments [Member] | Property and Casualty Insurance [Member]
Cash flow from operating activities:
Net earnings	8,679	7,630	19,794	26,945
Earnings from consolidated entities			0	0
Adjustments to reconcile net earnings to cash provided by operations:
Depreciation			0	0
Amortization of deferred policy acquisition costs	0	0	0	0
Amortization of premiums and accretion of discounts related to investments, inc			1,285	1,326
Amortization of debt issuance costs			0	0
Interest credited to policyholders			0	0
Change in allowance for losses on trade receivables			(147)	(174)
Change in allowance for inventory reserves			0	0
Net gain on sale of real and personal property			0	0
Net losses on disposal of real estate	0	0	0	0
Net (gain) loss on sale of investments			(75)	(223)
Net losses on equity investments			10,906	(3,695)
Deferred income tax			(1,594)	763
Net change in other operating assets and liabilities:
Reinsurance recoverables and trade receivables			(752)	1,567
Inventories			0	0
Prepaid expenses			0	0
Capitalization of deferred policy acquisition costs			0	0
Other assets			122	72
Related party assets			2,703	(813)
Accounts payable and accrued expenses			2,096	1,659
Policy benefits and losses, claims and loss expenses payable			(4,120)	(1,987)
Other policyholders' funds and liabilities			633	61
Deferred income			0	0
Related party liabilities			(617)	(2,414)
Net cash provided by operating activities			30,234	23,087
Cash flow from investing activities:
Escrow deposits			0	0
Purchase of:
Property, plant and equipment			0	0
Short term investments			(49,429)	(31,074)
Fixed maturity investments			(42,039)	(7,749)
Equity securities			(3,177)	0
Preferred stock			0	0
Real estate			(4,920)	0
Mortgage loans			(23,337)	(19,132)
Proceeds from sale of:
Property, plant and equipment			0	0
Short term investments			67,062	20,608
Fixed maturity investments			17,938	13,816
Equity securities			1,181	0
Preferred stock				2,000
Real estate			0
Mortgage loans			16,192	851
Net cash used by investing activities			(20,529)	(20,680)
Cash flow from financing activities:
Borrowings from credit facilities			0	0
Principal repayments on credit facilities			0	0
Payment of debt issuance costs			0	0
Capital lease payments			0	0
Securitization deposits			0
Voting Common Stock dividends paid			0	0
Series N Non-Voting Common Stock dividends			0
Investment contract deposits			0	0
Investment contract withdrawals			0	0
Net cash provided by (used in) financing activities			0	0
Effects of exchange rate on cash			0
Increase (decrease) in cash and cash equivalents			9,705
Cash and cash equivalents at beginning of period			10,800
Cash and cash equivalents at the end of period	20,505		20,505
Operating Segments [Member] | Life Insurance [Member]
Cash flow from operating activities:
Net earnings	4,020	2,773	6,626	10,866
Earnings from consolidated entities			0	0
Adjustments to reconcile net earnings to cash provided by operations:
Depreciation			0	0
Amortization of deferred policy acquisition costs	6,979	7,947	21,623	23,520
Amortization of premiums and accretion of discounts related to investments, inc			13,947	13,160
Amortization of debt issuance costs			0	0
Interest credited to policyholders			39,048	47,181
Change in allowance for losses on trade receivables			0	4
Change in allowance for inventory reserves			0	0
Net gain on sale of real and personal property			0	0
Net losses on disposal of real estate	0	0	0	0
Net (gain) loss on sale of investments			8,770	(3,272)
Net losses on equity investments			0	0
Deferred income tax			(2,416)	(4,544)
Net change in other operating assets and liabilities:
Reinsurance recoverables and trade receivables			3,513	1,465
Inventories			0	0
Prepaid expenses			0	0
Capitalization of deferred policy acquisition costs			(20,406)	(25,703)
Other assets			(730)	(107)
Related party assets			0	0
Accounts payable and accrued expenses			(919)	965
Policy benefits and losses, claims and loss expenses payable			(5,689)	7,226
Other policyholders' funds and liabilities			1,134	(2,871)
Deferred income			1,845	(1,213)
Related party liabilities			115	474
Net cash provided by operating activities			66,461	67,151
Cash flow from investing activities:
Escrow deposits			0	0
Purchase of:
Property, plant and equipment			0	0
Short term investments			(372)	0
Fixed maturity investments			(224,393)	(440,534)
Equity securities			(1,651)	(1,380)
Preferred stock			0	(8,000)
Real estate			(257)	(157)
Mortgage loans			(124,680)	(112,501)
Proceeds from sale of:
Property, plant and equipment			0	0
Short term investments			0	61
Fixed maturity investments			130,352	270,531
Equity securities			6	2,026
Preferred stock				0
Real estate			3,066
Mortgage loans			140,100	27,213
Net cash used by investing activities			(77,829)	(262,741)
Cash flow from financing activities:
Borrowings from credit facilities			0	0
Principal repayments on credit facilities			0	(11,187)
Payment of debt issuance costs			0	0
Capital lease payments			0	0
Securitization deposits			0
Voting Common Stock dividends paid			0	0
Series N Non-Voting Common Stock dividends			0
Investment contract deposits			258,157	271,657
Investment contract withdrawals			(236,742)	(177,777)
Net cash provided by (used in) financing activities			21,415	82,693
Effects of exchange rate on cash			0
Increase (decrease) in cash and cash equivalents			10,047
Cash and cash equivalents at beginning of period			50,124
Cash and cash equivalents at the end of period	60,171		60,171
Consolidation, Eliminations [Member]
Cash flow from operating activities:
Net earnings	(12,699)	(10,403)	(26,420)	(37,811)
Earnings from consolidated entities			26,420	37,811
Adjustments to reconcile net earnings to cash provided by operations:
Depreciation			0	0
Amortization of deferred policy acquisition costs	0	0	0	0
Amortization of premiums and accretion of discounts related to investments, inc			0	0
Amortization of debt issuance costs			0	0
Interest credited to policyholders			0	0
Change in allowance for losses on trade receivables			0	0
Change in allowance for inventory reserves			0	0
Net gain on sale of real and personal property			0	0
Net losses on disposal of real estate	0	0	0	0
Net (gain) loss on sale of investments			0	0
Net losses on equity investments			0	0
Deferred income tax			0	0
Net change in other operating assets and liabilities:
Reinsurance recoverables and trade receivables			0	0
Inventories			0	0
Prepaid expenses			0	0
Capitalization of deferred policy acquisition costs			0	0
Other assets			0	0
Related party assets			0	0
Accounts payable and accrued expenses			0	0
Policy benefits and losses, claims and loss expenses payable			0	0
Other policyholders' funds and liabilities			0	0
Deferred income			0	0
Related party liabilities			0	0
Net cash provided by operating activities			0	0
Cash flow from investing activities:
Escrow deposits			0	0
Purchase of:
Property, plant and equipment			3,066	0
Short term investments			0	0
Fixed maturity investments			0	0
Equity securities			0	0
Preferred stock			0	0
Real estate			0	0
Mortgage loans			0	0
Proceeds from sale of:
Property, plant and equipment			0	0
Short term investments			0	0
Fixed maturity investments			0	0
Equity securities			0	0
Preferred stock				0
Real estate			(3,066)
Mortgage loans			0	0
Net cash used by investing activities			0	0
Cash flow from financing activities:
Borrowings from credit facilities			0	0
Principal repayments on credit facilities			0	0
Payment of debt issuance costs			0	0
Capital lease payments			0	0
Securitization deposits			0
Voting Common Stock dividends paid			0	0
Series N Non-Voting Common Stock dividends			0
Investment contract deposits			0	0
Investment contract withdrawals			0	0
Net cash provided by (used in) financing activities			0	0
Effects of exchange rate on cash			0	0
Increase (decrease) in cash and cash equivalents			0	0
Cash and cash equivalents at beginning of period			0	0
Cash and cash equivalents at the end of period	$ 0	$ 0	$ 0	$ 0