Consolidating financial information by industry segment (Statement of Operations) (Details) - USD ($) $ in Thousands	12 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Mar. 31, 2020
Revenues:
Self-moving equipment rentals	$ 3,958,807	$ 3,083,317	$ 2,692,413
Self-storage revenues	617,120	477,262	418,741
Self-moving and self-storage products and service sales	351,447	344,929	265,091
Property management fees	35,194	31,603	30,406
Life insurance premiums	111,027	121,609	127,976
Property and casualty insurance premiums	86,518	68,779	66,053
Net investment and interest income	148,261	122,938	137,829
Other revenue	431,373	291,548	240,359
Total revenues	5,739,747	4,541,985	3,978,868
Costs and expenses:
Operating expenses	2,676,541	2,187,684	2,117,148
Commission expenses	429,581	329,609	288,332
Cost of sales	259,585	214,059	164,018
Benefits and losses	186,647	179,512	174,836
Amortization of deferred policy acquisition costs	33,854	28,293	31,219
Lease expense	29,910	28,470	26,882
Depreciation, net of (gains) losses on disposals	482,752	609,930	637,063
Net gains on disposal of real estate	(4,120)	3,281	(758)
Total costs and expenses	4,094,750	3,580,838	3,438,740
Earnings from operations before equity in earnings of subsidiaries	1,644,997	961,147	540,128
Equity in earnings of subsidiaries	0	0	0
Earnings from operations	1,644,997	961,147	540,128
Other components of net periodic benefit costs	(1,120)	(987)	(1,054)
Interest expense	(167,424)	(163,502)	(160,950)
Fees and amortization on early extinguishment of debt	(956)	0	0
Pretax earnings	1,475,497	796,658	378,124
Income tax expense	(352,211)	(185,802)	63,924
Earnings available to common shareholders	1,123,286	610,856	442,048
Operating Segments [Member] | Moving and Storage Consolidations [Member]
Revenues:
Self-moving equipment rentals	3,963,535	3,086,824	2,696,516
Self-storage revenues	617,120	477,262	418,741
Self-moving and self-storage products and service sales	351,447	344,929	265,091
Property management fees	35,194	31,603	30,406
Life insurance premiums	0	0	0
Property and casualty insurance premiums	0	0	0
Net investment and interest income	3,135	2,259	10,593
Other revenue	427,836	288,797	236,419
Total revenues	5,398,267	4,231,674	3,657,766
Costs and expenses:
Operating expenses	2,621,270	2,137,381	2,069,655
Commission expenses	429,581	329,609	288,332
Cost of sales	259,585	214,059	164,018
Benefits and losses	0	0	0
Amortization of deferred policy acquisition costs	0	0	0
Lease expense	31,973	30,551	27,494
Depreciation, net of (gains) losses on disposals	482,752	609,930	637,063
Net gains on disposal of real estate	(4,120)	3,281	(758)
Total costs and expenses	3,821,041	3,324,811	3,185,804
Earnings from operations before equity in earnings of subsidiaries	1,577,226	906,863	471,962
Equity in earnings of subsidiaries	54,746	44,441	55,789
Earnings from operations	1,631,972	951,304	527,751
Other components of net periodic benefit costs	(1,120)	(987)	(1,054)
Interest expense	(168,491)	(164,592)	(162,062)
Fees and amortization on early extinguishment of debt	(956)
Pretax earnings	1,461,405	785,725	364,635
Income tax expense	(338,119)	(174,869)	77,413
Earnings available to common shareholders	1,123,286	610,856	442,048
Operating Segments [Member] | Property and Casualty Insurance [Member]
Revenues:
Self-moving equipment rentals	0	0	0
Self-storage revenues	0	0	0
Self-moving and self-storage products and service sales	0	0	0
Property management fees	0	0	0
Life insurance premiums	0	0	0
Property and casualty insurance premiums	89,667	70,285	69,141
Net investment and interest income	25,376	16,452	19,923
Other revenue	0	0	0
Total revenues	115,043	86,737	89,064
Costs and expenses:
Operating expenses	42,456	35,450	33,770
Commission expenses	0	0	0
Cost of sales	0	0	0
Benefits and losses	22,448	18,558	12,410
Amortization of deferred policy acquisition costs	0	0	0
Lease expense	359	231	0
Depreciation, net of (gains) losses on disposals	0	0	0
Net gains on disposal of real estate	0	0	0
Total costs and expenses	65,263	54,239	46,180
Earnings from operations before equity in earnings of subsidiaries	49,780	32,498	42,884
Equity in earnings of subsidiaries	0	0	0
Earnings from operations	49,780	32,498	42,884
Other components of net periodic benefit costs	0	0	0
Interest expense	0	0	0
Fees and amortization on early extinguishment of debt	0
Pretax earnings	49,780	32,498	42,884
Income tax expense	(10,378)	(6,778)	(8,956)
Earnings available to common shareholders	39,402	25,720	33,928
Operating Segments [Member] | Life Insurance [Member]
Revenues:
Self-moving equipment rentals	0	0	0
Self-storage revenues	0	0	0
Self-moving and self-storage products and service sales	0	0	0
Property management fees	0	0	0
Life insurance premiums	111,027	121,609	127,976
Property and casualty insurance premiums	0	0	0
Net investment and interest income	123,809	107,745	109,018
Other revenue	3,976	3,280	4,470
Total revenues	238,812	232,634	241,464
Costs and expenses:
Operating expenses	21,112	20,376	21,425
Commission expenses	0	0	0
Cost of sales	0	0	0
Benefits and losses	164,199	160,954	162,426
Amortization of deferred policy acquisition costs	33,854	28,293	31,219
Lease expense	109	135	0
Depreciation, net of (gains) losses on disposals	0	0	0
Net gains on disposal of real estate	0	0	0
Total costs and expenses	219,274	209,758	215,070
Earnings from operations before equity in earnings of subsidiaries	19,538	22,876	26,394
Equity in earnings of subsidiaries	0	0	0
Earnings from operations	19,538	22,876	26,394
Other components of net periodic benefit costs	0	0	0
Interest expense	(480)	0	0
Fees and amortization on early extinguishment of debt	0
Pretax earnings	19,058	22,876	26,394
Income tax expense	(3,714)	(4,155)	(4,533)
Earnings available to common shareholders	15,344	18,721	21,861
Eliminations [Member]
Revenues:
Self-moving equipment rentals	(4,728)	(3,507)	(4,103)
Self-storage revenues	0	0	0
Self-moving and self-storage products and service sales	0	0	0
Property management fees	0	0	0
Life insurance premiums	0	0	0
Property and casualty insurance premiums	(3,149)	(1,506)	(3,088)
Net investment and interest income	(4,059)	(3,518)	(1,705)
Other revenue	(439)	(529)	(530)
Total revenues	(12,375)	(9,060)	(9,426)
Costs and expenses:
Operating expenses	(8,297)	(5,523)	(7,702)
Commission expenses	0	0	0
Cost of sales	0	0	0
Benefits and losses	0	0	0
Amortization of deferred policy acquisition costs	0	0	0
Lease expense	(2,531)	(2,447)	(612)
Depreciation, net of (gains) losses on disposals	0	0	0
Net gains on disposal of real estate	0	0	0
Total costs and expenses	(10,828)	(7,970)	(8,314)
Earnings from operations before equity in earnings of subsidiaries	(1,547)	(1,090)	(1,112)
Equity in earnings of subsidiaries	(54,746)	(44,441)	(55,789)
Earnings from operations	(56,293)	(45,531)	(56,901)
Other components of net periodic benefit costs	0	0	0
Interest expense	1,547	1,090	1,112
Fees and amortization on early extinguishment of debt	0
Pretax earnings	(54,746)	(44,441)	(55,789)
Income tax expense	0	0	0
Earnings available to common shareholders	$ (54,746)	$ (44,441)	$ (55,789)