Consolidating financial information by industry segment (Cash Flow Statements) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Cash flow from operating activities:
Net earnings	$ 352,015	$ 409,898	$ 686,017	$ 755,073
Earnings from consolidated entities			0	0
Adjustments to reconcile net earnings to cash provided by operations:
Depreciation			359,804	343,863
Amortization of deferred policy acquisition costs	6,972	6,750	14,644	15,573
Amortization of premiums and accretion of discounts related to investments, inc			10,249	9,151
Amortization of debt issuance costs			3,356	2,791
Interest credited to policyholders			24,690	31,894
Change in allowance for losses on trade receivables			(5,494)	222
Change in allowance for inventory reserves			7,125	8,352
Net gain on sale of real and personal property			(128,690)	(86,398)
Net losses on disposal of real estate	1,872	523	4,179	(3,907)
Net (gain) loss on sale of investments			7,207	(3,432)
Net losses on equity investments			7,963	(4,342)
Deferred income tax			103,828	138,916
Net change in other operating assets and liabilities:
Reinsurance recoverables and trade receivables			32,342	(3,771)
Inventories			(14,416)	(45,718)
Prepaid expenses			3	266,780
Capitalization of deferred policy acquisition costs			(14,900)	(17,807)
Other assets			2,432	(1,327)
Related party assets			(1,640)	(2,724)
Accounts payable and accrued expenses			64,297	91,548
Policy benefits and losses, claims and loss expenses payable			13,654	18,968
Other policyholders' funds and liabilities			1,314	(1,477)
Deferred income			9,458	7,592
Related party liabilities			742	(700)
Net cash provided by operating activities			1,188,164	1,519,120
Cash flow from investing activities:
Escrow deposits			9,688	(2,341)
Purchase of:
Property, plant and equipment			(1,335,528)	(1,039,688)
Short term investments			(36,173)	(21,669)
Fixed maturity investments			(202,265)	(415,640)
Equity securities			(4,356)	(36)
Preferred stock			0	(8,000)
Real estate			(4,931)	(124)
Mortgage loans			(75,635)	(106,963)
Proceeds from sale of:
Property, plant and equipment			329,611	306,946
Short term investments			33,373	16,673
Fixed maturity investments			106,527	230,043
Preferred stock			717	1,894
Mortgage loans			74,165	26,612
Net cash used by investing activities			(1,104,807)	(1,012,293)
Cash flow from financing activities:
Borrowings from credit facilities			792,654	987,048
Principal repayments on credit facilities			(441,019)	(227,072)
Payment of debt issuance costs			(3,942)	(2,092)
Capital lease payments			(65,831)	(87,500)
Securitization deposits			49	0
Common stock dividends paid			(19,608)	(19,608)
Investment contract deposits			169,017	199,426
Investment contract withdrawals			(139,917)	(116,021)
Net cash provided by (used in) financing activities			291,403	734,181
Effects on exchange rate on cash			(13,782)	(4,787)
Increase (decrease) in cash and cash equivalents			360,978	1,236,221
Cash and cash equivalents at the beginning of period			2,704,137	1,194,012
Cash and cash equivalents at the end of period	3,065,115	2,430,233	3,065,115	2,430,233
Operating Segments [Member] | Moving and Storage Consolidations [Member]
Cash flow from operating activities:
Net earnings	352,015	409,898	686,017	755,073
Earnings from consolidated entities			(13,721)	(27,408)
Adjustments to reconcile net earnings to cash provided by operations:
Depreciation			359,804	343,863
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			3,356	2,791
Interest credited to policyholders			0	0
Change in allowance for losses on trade receivables			(5,404)	253
Change in allowance for inventory reserves			7,125	8,352
Net gain on sale of real and personal property			(128,690)	(86,398)
Net losses on disposal of real estate	1,872	523	4,179	(3,907)
Net (gain) loss on sale of investments			0	0
Net losses on equity investments			0	0
Deferred income tax			107,281	140,780
Net change in other operating assets and liabilities:
Reinsurance recoverables and trade receivables			30,678	6,159
Inventories			(14,416)	(45,718)
Prepaid expenses			3	266,780
Capitalization of deferred policy acquisition costs			0	0
Other assets			2,877	(1,033)
Related party assets			(2,479)	(1,161)
Accounts payable and accrued expenses			65,366	89,479
Policy benefits and losses, claims and loss expenses payable			19,640	15,250
Other policyholders' funds and liabilities			0	0
Deferred income			7,809	8,626
Related party liabilities			460	543
Net cash provided by operating activities			1,129,885	1,472,324
Cash flow from investing activities:
Escrow deposits			9,688	(2,341)
Purchase of:
Property, plant and equipment			(1,335,528)	(1,039,688)
Short term investments			0	0
Fixed maturity investments			0	0
Equity securities			0	0
Preferred stock			0	0
Real estate			0	(12)
Mortgage loans			0	(12)
Proceeds from sale of:
Property, plant and equipment			329,611	306,946
Short term investments			0	0
Fixed maturity investments			0	0
Preferred stock			0	0
Mortgage loans			0	0
Net cash used by investing activities			(996,229)	(735,107)
Cash flow from financing activities:
Borrowings from credit facilities			792,654	987,048
Principal repayments on credit facilities			(441,019)	(226,791)
Payment of debt issuance costs			(3,942)	(2,092)
Capital lease payments			(65,831)	(87,500)
Securitization deposits			49
Common stock dividends paid			(19,608)	(19,608)
Investment contract deposits			0	0
Investment contract withdrawals			0	0
Net cash provided by (used in) financing activities			262,303	651,057
Effects on exchange rate on cash			(13,782)	(4,787)
Increase (decrease) in cash and cash equivalents			382,177	1,383,487
Cash and cash equivalents at the beginning of period			2,643,213	1,010,275
Cash and cash equivalents at the end of period	3,025,390	2,393,762	3,025,390	2,393,762
Operating Segments [Member] | Property and Casualty Insurance [Member]
Cash flow from operating activities:
Net earnings	4,519	12,013	11,115	19,315
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			857	754
Amortization of debt issuance costs			0	0
Interest credited to policyholders			0	0
Change in allowance for losses on trade receivables			(90)	(30)
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			(58)	(207)
Net losses on equity investments			7,963	(4,342)
Deferred income tax			(1,119)	865
Net change in other operating assets and liabilities:
Reinsurance recoverables and trade receivables			(1,088)	(148)
Inventories			0	0
Prepaid expenses			0	0
Capitalization of deferred policy acquisition costs			0	0
Other assets			(169)	(179)
Related party assets			839	(1,563)
Accounts payable and accrued expenses			1,396	1,547
Policy benefits and losses, claims and loss expenses payable			(3,381)	174
Other policyholders' funds and liabilities			112	(222)
Deferred income			0	0
Related party liabilities			(183)	(2,098)
Net cash provided by operating activities			16,194	13,866
Cash flow from investing activities:
Escrow deposits			0	0
Purchase of:
Property, plant and equipment			0	0
Short term investments			(35,975)	(21,669)
Fixed maturity investments			(18,573)	(7,749)
Equity securities			(2,705)	0
Preferred stock			0	0
Real estate			(4,920)	0
Mortgage loans			(12,715)	(10,700)
Proceeds from sale of:
Property, plant and equipment			0	0
Short term investments			33,373	16,594
Fixed maturity investments			10,587	10,728
Preferred stock			711	0
Mortgage loans			14,419	565
Net cash used by investing activities			(15,798)	(12,231)
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	0
Investment contract deposits			0	0
Investment contract withdrawals			0	0
Net cash provided by (used in) financing activities			0	0
Effects on exchange rate on cash			0	0
Increase (decrease) in cash and cash equivalents			396	1,635
Cash and cash equivalents at the beginning of period			10,800	5,658
Cash and cash equivalents at the end of period	11,196	7,293	11,196	7,293
Operating Segments [Member] | Life Insurance [Member]
Cash flow from operating activities:
Net earnings	1,536	6,276	2,606	8,093
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	6,972	6,750	14,644	15,573
Amortization of premiums and accretion of discounts related to investments, inc			9,392	8,397
Amortization of debt issuance costs			0	0
Interest credited to policyholders			24,690	31,894
Change in allowance for losses on trade receivables			0	(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			7,265	(3,225)
Net losses on equity investments			0	0
Deferred income tax			(2,334)	(2,729)
Net change in other operating assets and liabilities:
Reinsurance recoverables and trade receivables			2,752	(9,782)
Inventories			0	0
Prepaid expenses			0	0
Capitalization of deferred policy acquisition costs			(14,900)	(17,807)
Other assets			(276)	(115)
Related party assets			0	0
Accounts payable and accrued expenses			(2,465)	522
Policy benefits and losses, claims and loss expenses payable			(2,605)	3,544
Other policyholders' funds and liabilities			1,202	(1,255)
Deferred income			1,649	(1,034)
Related party liabilities			465	855
Net cash provided by operating activities			42,085	32,930
Cash flow from investing activities:
Escrow deposits			0	0
Purchase of:
Property, plant and equipment			0	0
Short term investments			(198)	0
Fixed maturity investments			(183,692)	(407,891)
Equity securities			(1,651)	(36)
Preferred stock			0	(8,000)
Real estate			(11)	(112)
Mortgage loans			(62,920)	(96,251)
Proceeds from sale of:
Property, plant and equipment			0	0
Short term investments			0	79
Fixed maturity investments			95,940	219,315
Preferred stock			6	1,894
Mortgage loans			59,746	26,047
Net cash used by investing activities			(92,780)	(264,955)
Cash flow from financing activities:
Borrowings from credit facilities			0	0
Principal repayments on credit facilities			0	(281)
Payment of debt issuance costs			0	0
Capital lease payments			0	0
Securitization deposits			0
Common stock dividends paid			0	0
Investment contract deposits			169,017	199,426
Investment contract withdrawals			(139,917)	(116,021)
Net cash provided by (used in) financing activities			29,100	83,124
Effects on exchange rate on cash			0	0
Increase (decrease) in cash and cash equivalents			(21,595)	(148,901)
Cash and cash equivalents at the beginning of period			50,124	178,079
Cash and cash equivalents at the end of period	28,529	29,178	28,529	29,178
Consolidation, Eliminations [Member]
Cash flow from operating activities:
Net earnings	(6,055)	(18,289)	(13,721)	(27,408)
Earnings from consolidated entities			13,721	27,408
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			0	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
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	0
Investment contract deposits			0	0
Investment contract withdrawals			0	0
Net cash provided by (used in) financing activities			0	0
Effects on 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 period	$ 0	$ 0	$ 0	$ 0