Consolidating financial information by industry segment (Statements of Operations) (Details) - USD ($) $ in Thousands	3 Months Ended
	Jun. 30, 2022	Jun. 30, 2021
Revenues:
Self-moving equipment rentals	$ 1,090,775	$ 1,035,377
Self-storage revenues	173,177	137,393
Self moving and self-storage products and service sales	109,351	104,885
Property management fees	9,139	8,449
Life insurance premiums	25,781	28,705
Property and casualty insurance premiums	19,972	16,869
Investment income interest and dividend	33,573	34,999
Other revenue	136,072	106,179
Total revenues	1,597,840	1,472,856
Costs and expenses:
Operating expenses	733,167	614,529
Commission expenses	118,493	113,149
Cost of sales	79,671	69,915
Benefits and losses	44,100	47,298
Amortization of deferred policy acquisition costs	7,672	8,823
Lease expense	7,475	7,647
Depreciation, net of (gains) losses on disposals	113,796	121,717
Net (gains) losses on disposal of real estate	2,307	(4,430)
Total costs and expenses	1,106,681	978,648
Earnings (loss) from operations before equity in earnings of subsidiaries	491,159	494,208
Equity in earnings of subsidiaries	0	0
Earnings from operations	491,159	494,208
Other components of net periodic benefit costs	(304)	(280)
Interest expense	(49,799)	(39,178)
Pretax earnings	441,056	454,750
Income tax expense	(107,054)	(109,575)
Earnings available to common stockholders	334,002	345,175
Operating Segments [Member] | Moving and Storage Consolidations [Member]
Revenues:
Self-moving equipment rentals	1,091,710	1,036,213
Self-storage revenues	173,177	137,393
Self moving and self-storage products and service sales	109,351	104,885
Property management fees	9,139	8,449
Life insurance premiums	0	0
Property and casualty insurance premiums	0	0
Investment income interest and dividend	4,940	680
Other revenue	135,281	105,634
Total revenues	1,523,598	1,393,254
Costs and expenses:
Operating expenses	719,794	601,831
Commission expenses	118,493	113,149
Cost of sales	79,671	69,915
Benefits and losses	0	0
Amortization of deferred policy acquisition costs	0	0
Lease expense	7,920	8,077
Depreciation, net of (gains) losses on disposals	113,796	121,717
Net (gains) losses on disposal of real estate	2,307	(4,430)
Total costs and expenses	1,041,981	910,259
Earnings (loss) from operations before equity in earnings of subsidiaries	481,617	482,995
Equity in earnings of subsidiaries	7,666	9,119
Earnings from operations	489,283	492,114
Other components of net periodic benefit costs	(304)	(280)
Interest expense	(50,061)	(39,443)
Pretax earnings	438,918	452,391
Income tax expense	(104,916)	(107,216)
Earnings available to common stockholders	334,002	345,175
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	20,830	17,443
Investment income interest and dividend	2,252	6,013
Other revenue	0	0
Total revenues	23,082	23,456
Costs and expenses:
Operating expenses	10,194	8,813
Commission expenses	0	0
Cost of sales	0	0
Benefits and losses	4,379	5,227
Amortization of deferred policy acquisition costs	0	0
Lease expense	158	184
Depreciation, net of (gains) losses on disposals	0	0
Net (gains) losses on disposal of real estate	0	0
Total costs and expenses	14,731	14,224
Earnings (loss) from operations before equity in earnings of subsidiaries	8,351	9,232
Equity in earnings of subsidiaries	0	0
Earnings from operations	8,351	9,232
Other components of net periodic benefit costs	0	0
Interest expense	0	0
Pretax earnings	8,351	9,232
Income tax expense	(1,755)	(1,930)
Earnings available to common stockholders	6,596	7,302
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	25,781	28,705
Property and casualty insurance premiums	0	0
Investment income interest and dividend	27,388	29,324
Other revenue	934	630
Total revenues	54,103	58,659
Costs and expenses:
Operating expenses	5,109	5,375
Commission expenses	0	0
Cost of sales	0	0
Benefits and losses	39,721	42,071
Amortization of deferred policy acquisition costs	7,672	8,823
Lease expense	28	24
Depreciation, net of (gains) losses on disposals	0	0
Net (gains) losses on disposal of real estate	0	0
Total costs and expenses	52,530	56,293
Earnings (loss) from operations before equity in earnings of subsidiaries	1,573	2,366
Equity in earnings of subsidiaries	0	0
Earnings from operations	1,573	2,366
Other components of net periodic benefit costs	0	0
Interest expense	(120)	(120)
Pretax earnings	1,453	2,246
Income tax expense	(383)	(429)
Earnings available to common stockholders	1,070	1,817
Consolidation, Eliminations [Member]
Revenues:
Self-moving equipment rentals	(935)	(836)
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	(858)	(574)
Investment income interest and dividend	(1,007)	(1,018)
Other revenue	(143)	(85)
Total revenues	(2,943)	(2,513)
Costs and expenses:
Operating expenses	(1,930)	(1,490)
Commission expenses	0	0
Cost of sales	0	0
Benefits and losses	0	0
Amortization of deferred policy acquisition costs	0	0
Lease expense	(631)	(638)
Depreciation, net of (gains) losses on disposals	0	0
Net (gains) losses on disposal of real estate	0	0
Total costs and expenses	(2,561)	(2,128)
Earnings (loss) from operations before equity in earnings of subsidiaries	(382)	(385)
Equity in earnings of subsidiaries	(7,666)	(9,119)
Earnings from operations	(8,048)	(9,504)
Other components of net periodic benefit costs	0	0
Interest expense	382	385
Pretax earnings	(7,666)	(9,119)
Income tax expense	0	0
Earnings available to common stockholders	$ (7,666)	$ (9,119)