Consolidating financial information by industry segment (Statements of Operations) (Details) - USD ($) $ in Thousands	3 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
Revenues:
Self-moving equipment rentals	$ 1,035,377	$ 654,285
Self-storage revenues	137,393	108,955
Self moving and self-storage products and service sales	104,885	91,350
Property management fees	8,449	7,347
Life insurance premiums	28,705	30,908
Property and casualty insurance premiums	16,869	13,734
Investment income interest and dividend	34,999	16,982
Other revenue	106,179	63,676
Total revenues	1,472,856	987,237
Costs and expenses:
Operating expenses	614,529	492,662
Commission expenses	113,149	69,175
Cost of sales	69,915	52,831
Benefits and losses	47,298	39,577
Amortization of deferred policy acquisition costs	8,823	6,888
Lease expense	7,647	6,603
Depreciation, net of (gains) losses on disposals	121,717	165,671
Net (gains) losses on disposal of real estate	(4,430)	(256)
Total costs and expenses	978,648	833,151
Earnings (loss) from operations before equity in earnings of subsidiaries	494,208	154,086
Equity in earnings of subsidiaries	0	0
Earnings from operations	494,208	154,086
Other components of net periodic benefit costs	(280)	(247)
Interest expense	(39,178)	(39,521)
Pretax earnings	454,750	114,318
Income tax expense	(109,575)	(26,592)
Earnings available to common stockholders	345,175	87,726
Operating Segments [Member] | Moving and Storage Consolidations [Member]
Revenues:
Self-moving equipment rentals	1,036,213	654,913
Self-storage revenues	137,393	108,955
Self moving and self-storage products and service sales	104,885	91,350
Property management fees	8,449	7,347
Life insurance premiums	0	0
Property and casualty insurance premiums	0	0
Investment income interest and dividend	680	662
Other revenue	105,634	63,073
Total revenues	1,393,254	926,300
Costs and expenses:
Operating expenses	601,831	480,081
Commission expenses	113,149	69,175
Cost of sales	69,915	52,831
Benefits and losses	0	0
Amortization of deferred policy acquisition costs	0	0
Lease expense	8,077	7,137
Depreciation, net of (gains) losses on disposals	121,717	165,671
Net (gains) losses on disposal of real estate	(4,430)	(256)
Total costs and expenses	910,259	774,639
Earnings (loss) from operations before equity in earnings of subsidiaries	482,995	151,661
Equity in earnings of subsidiaries	9,119	2,395
Earnings from operations	492,114	154,056
Other components of net periodic benefit costs	(280)	(247)
Interest expense	(39,443)	(39,794)
Pretax earnings	452,391	114,015
Income tax expense	(107,216)	(26,289)
Earnings available to common stockholders	345,175	87,726
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	17,443	14,507
Investment income interest and dividend	6,013	(873)
Other revenue	0	0
Total revenues	23,456	13,634
Costs and expenses:
Operating expenses	8,813	8,825
Commission expenses	0	0
Cost of sales	0	0
Benefits and losses	5,227	4,030
Amortization of deferred policy acquisition costs	0	0
Lease expense	184	1
Depreciation, net of (gains) losses on disposals	0	0
Net (gains) losses on disposal of real estate	0	0
Total costs and expenses	14,224	12,856
Earnings (loss) from operations before equity in earnings of subsidiaries	9,232	778
Equity in earnings of subsidiaries	0	0
Earnings from operations	9,232	778
Other components of net periodic benefit costs	0	0
Interest expense	0	0
Pretax earnings	9,232	778
Income tax expense	(1,930)	(162)
Earnings available to common stockholders	7,302	616
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	28,705	30,908
Property and casualty insurance premiums	0	0
Investment income interest and dividend	29,324	18,006
Other revenue	630	739
Total revenues	58,659	49,653
Costs and expenses:
Operating expenses	5,375	5,288
Commission expenses	0	0
Cost of sales	0	0
Benefits and losses	42,071	35,547
Amortization of deferred policy acquisition costs	8,823	6,888
Lease expense	24	10
Depreciation, net of (gains) losses on disposals	0	0
Net (gains) losses on disposal of real estate	0	0
Total costs and expenses	56,293	47,733
Earnings (loss) from operations before equity in earnings of subsidiaries	2,366	1,920
Equity in earnings of subsidiaries	0	0
Earnings from operations	2,366	1,920
Other components of net periodic benefit costs	0	0
Interest expense	(120)	0
Pretax earnings	2,246	1,920
Income tax expense	(429)	(141)
Earnings available to common stockholders	1,817	1,779
Consolidation, Eliminations [Member]
Revenues:
Self-moving equipment rentals	(836)	(628)
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	(574)	(773)
Investment income interest and dividend	(1,018)	(813)
Other revenue	(85)	(136)
Total revenues	(2,513)	(2,350)
Costs and expenses:
Operating expenses	(1,490)	(1,532)
Commission expenses	0	0
Cost of sales	0	0
Benefits and losses	0	0
Amortization of deferred policy acquisition costs	0	0
Lease expense	(638)	(545)
Depreciation, net of (gains) losses on disposals	0	0
Net (gains) losses on disposal of real estate	0	0
Total costs and expenses	(2,128)	(2,077)
Earnings (loss) from operations before equity in earnings of subsidiaries	(385)	(273)
Equity in earnings of subsidiaries	(9,119)	(2,395)
Earnings from operations	(9,504)	(2,668)
Other components of net periodic benefit costs	0	0
Interest expense	385	273
Pretax earnings	(9,119)	(2,395)
Income tax expense	0	0
Earnings available to common stockholders	$ (9,119)	$ (2,395)