Consolidating financial information by industry segment (Statements of Operations) (Details) - USD ($) $ in Thousands	3 Months Ended
	Jun. 30, 2023	Jun. 30, 2022
Revenues:
Self-moving equipment rentals	$ 999,206	$ 1,090,775
Self-storage revenues	198,961	173,177
Self moving and self-storage products and service sales	100,872	109,351
Property management fees	9,177	9,139
Life insurance premiums	23,131	25,781
Property and casualty insurance premiums	20,322	19,972
Investment income interest and dividend	64,592	33,573
Other revenue	124,047	136,072
Total revenues	1,540,308	1,597,840
Costs and expenses:
Operating expenses	763,241	733,167
Commission expenses	106,927	118,493
Cost of sales	70,675	79,671
Benefits and losses	45,344	39,757
Amortization of deferred policy acquisition costs	8,045	7,672
Lease expense	7,583	7,475
Depreciation, net of (gains) losses on disposals	137,814	113,796
Net (gains) losses on disposal of real estate	1,021	2,307
Total costs and expenses	1,140,650	1,102,338
Earnings (loss) from operations before equity in earnings of subsidiaries	399,658	495,502
Equity in earnings of subsidiaries	0	0
Earnings from operations	399,658	495,502
Other components of net periodic benefit costs	(365)	(304)
Interest expense	(60,598)	(49,799)
Pretax earnings	338,695	445,399
Income tax expense	(81,857)	(107,054)
Earnings available to common stockholders	256,838	338,345
Operating Segments [Member] | Moving and Storage Consolidations [Member]
Revenues:
Self-moving equipment rentals	1,000,079	1,091,710
Self-storage revenues	198,961	173,177
Self moving and self-storage products and service sales	100,872	109,351
Property management fees	9,177	9,139
Life insurance premiums	0	0
Property and casualty insurance premiums	0	0
Investment income interest and dividend	27,295	4,940
Other revenue	123,129	135,281
Total revenues	1,459,513	1,523,598
Costs and expenses:
Operating expenses	748,283	719,794
Commission expenses	106,927	118,493
Cost of sales	70,675	79,671
Benefits and losses	0	0
Amortization of deferred policy acquisition costs	0	0
Lease expense	8,102	7,920
Depreciation, net of (gains) losses on disposals	137,814	113,796
Net (gains) losses on disposal of real estate	1,021	2,307
Total costs and expenses	1,072,822	1,041,981
Earnings (loss) from operations before equity in earnings of subsidiaries	386,691	481,617
Equity in earnings of subsidiaries	10,230	12,009
Earnings from operations	396,921	493,626
Other components of net periodic benefit costs	(365)	(304)
Interest expense	(60,849)	(50,061)
Pretax earnings	335,707	443,261
Income tax expense	(78,869)	(104,916)
Earnings available to common stockholders	256,838	338,345
Operating Segments [Member] | Property and Casualty Insurance [Member]
Revenues:
Self-moving equipment rentals	0	0
Self-storage revenues	0	0
Self moving and self-storage products and service sales	0	0
Property management fees	0	0
Life insurance premiums	0	0
Property and casualty insurance premiums	21,047	20,830
Investment income interest and dividend	6,792	2,252
Other revenue	0	0
Total revenues	27,839	23,082
Costs and expenses:
Operating expenses	11,307	10,194
Commission expenses	0	0
Cost of sales	0	0
Benefits and losses	4,458	4,379
Amortization of deferred policy acquisition costs	0	0
Lease expense	92	158
Depreciation, net of (gains) losses on disposals	0	0
Net (gains) losses on disposal of real estate	0	0
Total costs and expenses	15,857	14,731
Earnings (loss) from operations before equity in earnings of subsidiaries	11,982	8,351
Equity in earnings of subsidiaries	0	0
Earnings from operations	11,982	8,351
Other components of net periodic benefit costs	0	0
Interest expense	0	0
Pretax earnings	11,982	8,351
Income tax expense	(2,472)	(1,755)
Earnings available to common stockholders	9,510	6,596
Operating Segments [Member] | Life Insurance [Member]
Revenues:
Self-moving equipment rentals	0	0
Self-storage revenues	0	0
Self moving and self-storage products and service sales	0	0
Property management fees	0	0
Life insurance premiums	23,131	25,781
Property and casualty insurance premiums	0	0
Investment income interest and dividend	31,511	27,388
Other revenue	1,039	934
Total revenues	55,681	54,103
Costs and expenses:
Operating expenses	5,366	5,109
Commission expenses	0	0
Cost of sales	0	0
Benefits and losses	40,886	35,378
Amortization of deferred policy acquisition costs	8,045	7,672
Lease expense	28	28
Depreciation, net of (gains) losses on disposals	0	0
Net (gains) losses on disposal of real estate	0	0
Total costs and expenses	54,325	48,187
Earnings (loss) from operations before equity in earnings of subsidiaries	1,356	5,916
Equity in earnings of subsidiaries	0	0
Earnings from operations	1,356	5,916
Other components of net periodic benefit costs	0	0
Interest expense	(120)	(120)
Pretax earnings	1,236	5,796
Income tax expense	(516)	(383)
Earnings available to common stockholders	720	5,413
Consolidation, Eliminations [Member]
Revenues:
Self-moving equipment rentals	(873)	(935)
Self-storage revenues	0	0
Self moving and self-storage products and service sales	0	0
Property management fees	0	0
Life insurance premiums	0	0
Property and casualty insurance premiums	(725)	(858)
Investment income interest and dividend	(1,006)	(1,007)
Other revenue	(121)	(143)
Total revenues	(2,725)	(2,943)
Costs and expenses:
Operating expenses	(1,715)	(1,930)
Commission expenses	0	0
Cost of sales	0	0
Benefits and losses	0	0
Amortization of deferred policy acquisition costs	0	0
Lease expense	(639)	(631)
Depreciation, net of (gains) losses on disposals	0	0
Net (gains) losses on disposal of real estate	0	0
Total costs and expenses	(2,354)	(2,561)
Earnings (loss) from operations before equity in earnings of subsidiaries	(371)	(382)
Equity in earnings of subsidiaries	(10,230)	(12,009)
Earnings from operations	(10,601)	(12,391)
Other components of net periodic benefit costs	0	0
Interest expense	371	382
Pretax earnings	(10,230)	(12,009)
Income tax expense	0	0
Earnings available to common stockholders	$ (10,230)	$ (12,009)