Consolidating financial information by industry segment (Statements of Operations) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2022	Dec. 31, 2021
Revenues:
Self-moving equipment rentals	$ 898,819	$ 975,552	$ 3,151,619	$ 3,189,990
Self-storage revenues	190,483	159,424	549,246	450,302
Self moving and self-storage products and service sales	74,851	75,402	281,066	272,478
Property management fees	10,080	9,651	28,496	26,847
Life insurance premiums	24,399	27,010	75,636	84,628
Property and casualty insurance premiums	26,852	25,618	72,542	64,986
Net investment and interest income	52,294	31,184	116,376	102,963
Other revenue	97,558	100,495	401,059	349,252
Total revenues	1,375,336	1,404,336	4,676,040	4,541,446
Costs and expenses:
Operating expenses	733,469	658,095	2,278,230	1,968,698
Commission expenses	95,980	105,155	339,814	346,200
Cost of sales	54,616	57,042	206,912	193,448
Benefits and losses	41,372	47,266	122,835	139,194
Amortization of deferred policy acquisition costs	6,979	7,947	21,623	23,520
Lease expense	7,792	7,394	22,951	22,482
Depreciation, net of (gains) losses on disposals	113,866	103,736	344,980	361,201
Net (gains) losses on disposal of real estate	859	977	5,038	(2,930)
Total costs and expenses	1,054,933	987,612	3,342,383	3,051,813
Earnings (loss) from operations before equity in earnings of subsidiaries	320,403	416,724	1,333,657	1,489,633
Equity in earnings of subsidiaries	0	0	0	0
Earnings from operations	320,403	416,724	1,333,657	1,489,633
Other components of net periodic benefit costs	(304)	(280)	(912)	(840)
Interest expense	(59,041)	(44,042)	(166,033)	(122,765)
Fees on early extinguishment of debt	(50)	(956)	(1,009)	(956)
Pretax earnings	261,008	371,446	1,165,703	1,365,072
Income tax expense	(61,764)	(89,980)	(280,442)	(328,533)
Earnings available to common stockholders	199,244	281,466	885,261	1,036,539
Operating Segments [Member] | Moving and Storage Consolidations [Member]
Revenues:
Self-moving equipment rentals	900,209	977,052	3,155,295	3,193,594
Self-storage revenues	190,483	159,424	549,246	450,302
Self moving and self-storage products and service sales	74,851	75,402	281,066	272,478
Property management fees	10,080	9,651	28,496	26,847
Life insurance premiums	0	0	0	0
Property and casualty insurance premiums	0	0	0	0
Net investment and interest income	24,450	666	44,467	2,021
Other revenue	96,334	99,385	398,293	346,591
Total revenues	1,296,407	1,321,580	4,456,863	4,291,833
Costs and expenses:
Operating expenses	718,067	642,900	2,234,359	1,927,060
Commission expenses	95,980	105,155	339,814	346,200
Cost of sales	54,616	57,042	206,912	193,448
Benefits and losses	0	0	0	0
Amortization of deferred policy acquisition costs	0	0	0	0
Lease expense	8,302	7,917	24,483	24,018
Depreciation, net of (gains) losses on disposals	113,866	103,736	344,980	361,201
Net (gains) losses on disposal of real estate	859	977	5,038	(2,930)
Total costs and expenses	991,690	917,727	3,155,586	2,848,997
Earnings (loss) from operations before equity in earnings of subsidiaries	304,717	403,853	1,301,277	1,442,836
Equity in earnings of subsidiaries	12,699	10,403	26,420	37,811
Earnings from operations	317,416	414,256	1,327,697	1,480,647
Other components of net periodic benefit costs	(304)	(280)	(912)	(840)
Interest expense	(59,294)	(44,311)	(166,814)	(123,568)
Fees on early extinguishment of debt	(50)	(956)	(1,009)	(956)
Pretax earnings	257,768	368,709	1,158,962	1,355,283
Income tax expense	(58,524)	(87,243)	(273,701)	(318,744)
Earnings available to common stockholders	199,244	281,466	885,261	1,036,539
Operating Segments [Member] | Property and Casualty Insurance [Member]
Revenues:
Self-moving equipment rentals	0	0	0	0
Self-storage revenues	0	0	0	0
Self moving and self-storage products and service sales	0	0	0	0
Property management fees	0	0	0	0
Life insurance premiums	0	0	0	0
Property and casualty insurance premiums	26,852	26,477	73,642	67,277
Net investment and interest income	1,614	3,343	1,269	15,538
Other revenue	0	0	0	0
Total revenues	28,466	29,820	74,911	82,815
Costs and expenses:
Operating expenses	11,790	12,198	33,560	31,779
Commission expenses	0	0	0	0
Cost of sales	0	0	0	0
Benefits and losses	5,737	7,892	16,191	16,679
Amortization of deferred policy acquisition costs	0	0	0	0
Lease expense	93	73	277	279
Depreciation, net of (gains) losses on disposals	0	0	0	0
Net (gains) losses on disposal of real estate	0	0	0	0
Total costs and expenses	17,620	20,163	50,028	48,737
Earnings (loss) from operations before equity in earnings of subsidiaries	10,846	9,657	24,883	34,078
Equity in earnings of subsidiaries	0	0	0	0
Earnings from operations	10,846	9,657	24,883	34,078
Other components of net periodic benefit costs	0	0	0	0
Interest expense	0	0	0	0
Fees on early extinguishment of debt	0	0	0	0
Pretax earnings	10,846	9,657	24,883	34,078
Income tax expense	(2,167)	(2,027)	(5,089)	(7,133)
Earnings available to common stockholders	8,679	7,630	19,794	26,945
Operating Segments [Member] | Life Insurance [Member]
Revenues:
Self-moving equipment rentals	0	0	0	0
Self-storage revenues	0	0	0	0
Self moving and self-storage products and service sales	0	0	0	0
Property management fees	0	0	0	0
Life insurance premiums	24,399	27,010	75,636	84,628
Property and casualty insurance premiums	0	0	0	0
Net investment and interest income	27,230	28,182	73,659	88,448
Other revenue	1,333	1,225	3,466	2,985
Total revenues	52,962	56,417	152,761	176,061
Costs and expenses:
Operating expenses	5,109	5,465	15,776	16,063
Commission expenses	0	0	0	0
Cost of sales	0	0	0	0
Benefits and losses	35,635	39,374	106,644	122,515
Amortization of deferred policy acquisition costs	6,979	7,947	21,623	23,520
Lease expense	26	28	80	81
Depreciation, net of (gains) losses on disposals	0	0	0	0
Net (gains) losses on disposal of real estate	0	0	0	0
Total costs and expenses	47,749	52,814	144,123	162,179
Earnings (loss) from operations before equity in earnings of subsidiaries	5,213	3,603	8,638	13,882
Equity in earnings of subsidiaries	0	0	0	0
Earnings from operations	5,213	3,603	8,638	13,882
Other components of net periodic benefit costs	0	0	0	0
Interest expense	(120)	(120)	(360)	(360)
Fees on early extinguishment of debt	0	0	0	0
Pretax earnings	5,093	3,483	8,278	13,522
Income tax expense	(1,073)	(710)	(1,652)	(2,656)
Earnings available to common stockholders	4,020	2,773	6,626	10,866
Consolidation, Eliminations [Member]
Revenues:
Self-moving equipment rentals	(1,390)	(1,500)	(3,676)	(3,604)
Self-storage revenues	0	0	0	0
Self moving and self-storage products and service sales	0	0	0	0
Property management fees	0	0	0	0
Life insurance premiums	0	0	0	0
Property and casualty insurance premiums	0	(859)	(1,100)	(2,291)
Net investment and interest income	(1,000)	(1,007)	(3,019)	(3,044)
Other revenue	(109)	(115)	(700)	(324)
Total revenues	(2,499)	(3,481)	(8,495)	(9,263)
Costs and expenses:
Operating expenses	(1,497)	(2,468)	(5,465)	(6,204)
Commission expenses	0	0	0	0
Cost of sales	0	0	0	0
Benefits and losses	0	0	0	0
Amortization of deferred policy acquisition costs	0	0	0	0
Lease expense	(629)	(624)	(1,889)	(1,896)
Depreciation, net of (gains) losses on disposals	0	0	0	0
Net (gains) losses on disposal of real estate	0	0	0	0
Total costs and expenses	(2,126)	(3,092)	(7,354)	(8,100)
Earnings (loss) from operations before equity in earnings of subsidiaries	(373)	(389)	(1,141)	(1,163)
Equity in earnings of subsidiaries	(12,699)	(10,403)	(26,420)	(37,811)
Earnings from operations	(13,072)	(10,792)	(27,561)	(38,974)
Other components of net periodic benefit costs	0	0	0	0
Interest expense	373	389	1,141	1,163
Fees on early extinguishment of debt	0	0	0	0
Pretax earnings	(12,699)	(10,403)	(26,420)	(37,811)
Income tax expense	0	0	0	0
Earnings available to common stockholders	$ (12,699)	$ (10,403)	$ (26,420)	$ (37,811)