Consolidating financial information by industry segment (Cash Flow Statements) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2021	Dec. 31, 2020
Cash flow from operating activities:
Net earnings	$ 281,466	$ 182,985	$ 1,036,539	$ 537,076
Earnings from consolidated entities			0	0
Adjustments to reconcile net earnings to cash provided by operations:
Depreciation			519,181	495,794
Amortization of deferred policy acquisition costs	7,947	6,572	23,520	19,012
Amortization of premiums and accretion of discounts related to investments, net			14,486	10,197
Amortization of debt issuance costs			4,200	4,645
Interest credited to policyholders			47,181	38,672
Change in allowance for losses on trade receivables			1,243	(574)
Change in allowance for inventory reserves			9,799	3,259
Net gain on sale of real and personal property			(157,980)	(40,083)
Net losses on disposal of real estate	977	1,124	(2,930)	4,293
Net (gain) loss on sale of investments			(3,495)	(5,644)
Net losses on equity investments			(3,695)	669
Deferred income tax			130,760	117,025
Net change in other operating assets and liabilities:
Reinsurance recoverables and trade receivables			(7,371)	(39,499)
Inventories			(70,796)	(6,349)
Prepaid expenses			257,591	112,428
Capitalization of deferred policy acquisition costs			(25,703)	(24,903)
Other assets			1,178	30,120
Related party assets			(18,683)	(20,794)
Accounts payable and accrued expenses			33,258	97,151
Policy benefits and losses, claims and loss expenses payable			6,411	14,096
Other policyholders' funds and liabilities			(2,810)	24,677
Deferred income			(526)	6,851
Related party liabilities			(2,207)	(1,566)
Net cash provided by operating activities			1,789,151	1,376,553
Cash flow from investing activities:
Escrow deposits			5,695	(1,978)
Purchase of:
Property, plant and equipment			(1,652,984)	(961,995)
Short term investments			(31,074)	(38,790)
Fixed maturity investments			(448,283)	(352,307)
Equity securities			(1,380)	(838)
Preferred stock			(8,000)	(16,144)
Real estate			(190)	(274)
Mortgage loans			(131,633)	(92,281)
Proceeds from sale of:
Property, plant and equipment			483,783	434,860
Short term investments			20,669	38,830
Fixed maturity investments			284,347	331,407
Equity securities			2,026	72
Preferred stock			2,000	1,200
Mortgage loans			28,064	4,744
Net cash used by investing activities			(1,446,960)	(653,494)
Cash flow from financing activities:
Borrowings from credit facilities			1,202,412	790,532
Principal repayments on credit facilities			(333,419)	(568,068)
Payment of debt issuance costs			(8,006)	(5,020)
Capital lease payments			(129,150)	(173,520)
Securitization deposits				(49,019)
Common stock dividends paid			(29,412)	(49,019)
Net contribution from (to) related party			0	22,600
Investment contract deposits			271,657	326,055
Investment contract withdrawals			(177,777)	(169,008)
Net cash provided by (used in) financing activities			796,305	174,552
Effects of exchange rate on cash			(5,046)	6,877
Increase (decrease) in cash and cash equivalents			1,133,450	904,488
Cash and cash equivalents at the beginning of period			1,194,012	494,352
Cash and cash equivalents at the end of the period	2,327,462	1,398,840	2,327,462	1,398,840
Operating Segments [Member] | Moving and Storage Consolidations [Member]
Cash flow from operating activities:
Net earnings	281,466	182,985	1,036,539	537,076
Earnings from consolidated entities			(37,811)	(32,850)
Adjustments to reconcile net earnings to cash provided by operations:
Depreciation			519,181	495,794
Amortization of deferred policy acquisition costs	0	0	0	0
Amortization of premiums and accretion of discounts related to investments, net			0	0
Amortization of debt issuance costs			4,200	4,645
Interest credited to policyholders			0	0
Change in allowance for losses on trade receivables			1,413	(573)
Change in allowance for inventory reserves			9,799	3,259
Net gain on sale of real and personal property			(157,980)	(40,083)
Net losses on disposal of real estate	977	1,124	(2,930)	4,293
Net (gain) loss on sale of investments			0	0
Net losses on equity investments			0	0
Deferred income tax			134,541	116,099
Net change in other operating assets and liabilities:
Reinsurance recoverables and trade receivables			(10,403)	(39,327)
Inventories			(70,796)	(6,349)
Prepaid expenses			257,591	112,428
Capitalization of deferred policy acquisition costs			0	0
Other assets			1,213	30,337
Related party assets			(17,870)	(20,643)
Accounts payable and accrued expenses			30,634	96,269
Policy benefits and losses, claims and loss expenses payable			1,172	10,526
Other policyholders' funds and liabilities			0	0
Deferred income			687	5,483
Related party liabilities			(267)	749
Net cash provided by operating activities			1,698,913	1,277,133
Cash flow from investing activities:
Escrow deposits			5,695	(1,978)
Purchase of:
Property, plant and equipment			(1,652,984)	(961,995)
Short term investments			0	0
Fixed maturity investments			0	0
Equity securities			0	0
Preferred stock			0
Real estate			(33)	0
Mortgage loans			0	0
Proceeds from sale of:
Property, plant and equipment			483,783	434,860
Short term investments			0	0
Fixed maturity investments			0	0
Equity securities			0	0
Preferred stock			0	0
Mortgage loans			0	0
Net cash used by investing activities			(1,163,539)	(529,113)
Cash flow from financing activities:
Borrowings from credit facilities			1,202,412	780,932
Principal repayments on credit facilities			(322,232)	(558,280)
Payment of debt issuance costs			(8,006)	(5,020)
Capital lease payments			(129,150)	(173,520)
Securitization deposits				(49,019)
Common stock dividends paid			(29,412)
Net contribution from (to) related party				41,199
Investment contract deposits			0	0
Investment contract withdrawals			0	0
Net cash provided by (used in) financing activities			713,612	36,292
Effects of exchange rate on cash			(5,046)	6,877
Increase (decrease) in cash and cash equivalents			1,243,940	791,189
Cash and cash equivalents at the beginning of period			1,010,275	459,078
Cash and cash equivalents at the end of the period	2,254,215	1,250,267	2,254,215	1,250,267
Operating Segments [Member] | Property and Casualty Insurance [Member]
Cash flow from operating activities:
Net earnings	7,630	9,086	26,945	19,217
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, net			1,326	1,180
Amortization of debt issuance costs			0	0
Interest credited to policyholders			0	0
Change in allowance for losses on trade receivables			(174)	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			(223)	(86)
Net losses on equity investments			(3,695)	669
Deferred income tax			763	1,685
Net change in other operating assets and liabilities:
Reinsurance recoverables and trade receivables			1,567	5,880
Inventories			0	0
Prepaid expenses			0	0
Capitalization of deferred policy acquisition costs			0	0
Other assets			72	286
Related party assets			(813)	(151)
Accounts payable and accrued expenses			1,659	(2,106)
Policy benefits and losses, claims and loss expenses payable			(1,987)	(8,824)
Other policyholders' funds and liabilities			61	(5,671)
Deferred income			0	0
Related party liabilities			(2,414)	(946)
Net cash provided by operating activities			23,087	11,133
Cash flow from investing activities:
Escrow deposits			0	0
Purchase of:
Property, plant and equipment			0	0
Short term investments			(31,074)	(38,789)
Fixed maturity investments			(7,749)	(10,438)
Equity securities			0	0
Preferred stock			0
Real estate			0	0
Mortgage loans			(19,132)	(14,780)
Proceeds from sale of:
Property, plant and equipment			0	0
Short term investments			20,608	38,830
Fixed maturity investments			13,816	14,217
Equity securities			0	0
Preferred stock			2,000	1,200
Mortgage loans			851	879
Net cash used by investing activities			(20,680)	(8,881)
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
Common stock dividends paid			0
Net contribution from (to) related party				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			2,407	2,252
Cash and cash equivalents at the beginning of period			5,658	4,794
Cash and cash equivalents at the end of the period	8,065	7,046	8,065	7,046
Operating Segments [Member] | Life Insurance [Member]
Cash flow from operating activities:
Net earnings	2,773	7,031	10,866	13,633
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	7,947	6,572	23,520	19,012
Amortization of premiums and accretion of discounts related to investments, net			13,160	9,017
Amortization of debt issuance costs			0	0
Interest credited to policyholders			47,181	38,672
Change in allowance for losses on trade receivables			4	(1)
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			(3,272)	(5,558)
Net losses on equity investments			0	0
Deferred income tax			(4,544)	(759)
Net change in other operating assets and liabilities:
Reinsurance recoverables and trade receivables			1,465	(6,052)
Inventories			0	0
Prepaid expenses			0	0
Capitalization of deferred policy acquisition costs			(25,703)	(24,903)
Other assets			(107)	(503)
Related party assets			0	0
Accounts payable and accrued expenses			965	2,988
Policy benefits and losses, claims and loss expenses payable			7,226	12,394
Other policyholders' funds and liabilities			(2,871)	30,348
Deferred income			(1,213)	1,368
Related party liabilities			474	(1,369)
Net cash provided by operating activities			67,151	88,287
Cash flow from investing activities:
Escrow deposits			0	0
Purchase of:
Property, plant and equipment			0	0
Short term investments			0	(1)
Fixed maturity investments			(440,534)	(341,869)
Equity securities			(1,380)	(838)
Preferred stock			(8,000)
Real estate			(157)	(274)
Mortgage loans			(112,501)	(77,501)
Proceeds from sale of:
Property, plant and equipment			0	0
Short term investments			61	0
Fixed maturity investments			270,531	317,190
Equity securities			2,026	72
Preferred stock			0	0
Mortgage loans			27,213	3,865
Net cash used by investing activities			(262,741)	(115,500)
Cash flow from financing activities:
Borrowings from credit facilities			0	9,600
Principal repayments on credit facilities			(11,187)	(9,788)
Payment of debt issuance costs			0	0
Capital lease payments			0	0
Securitization deposits				0
Common stock dividends paid			0
Net contribution from (to) related party				(18,599)
Investment contract deposits			271,657	326,055
Investment contract withdrawals			(177,777)	(169,008)
Net cash provided by (used in) financing activities			82,693	138,260
Effects of exchange rate on cash			0	0
Increase (decrease) in cash and cash equivalents			(112,897)	111,047
Cash and cash equivalents at the beginning of period			178,079	30,480
Cash and cash equivalents at the end of the period	65,182	141,527	65,182	141,527
Consolidation, Eliminations [Member]
Cash flow from operating activities:
Net earnings	(10,403)	(16,117)	(37,811)	(32,850)
Earnings from consolidated entities			37,811	32,850
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, net			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			0	0
Short term investments			0	0
Fixed maturity investments			0	0
Equity securities			0	0
Preferred stock			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	0
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
Common stock dividends paid			0
Net contribution from (to) related party				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 the beginning of period			0	0
Cash and cash equivalents at the end of the period	$ 0	$ 0	$ 0	$ 0