Consolidating financial information by industry segment (Statements of Operations) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Revenues:
Self-moving equipment rentals	$ 1,162,025	$ 1,179,061	$ 2,252,800	$ 2,214,438
Self-storage revenues	185,586	153,485	358,763	290,878
Self moving and self-storage products and service sales	96,864	92,191	206,215	197,076
Property management fees	9,277	8,747	18,416	17,196
Life insurance premiums	25,456	28,913	51,237	57,618
Property and casualty insurance premiums	25,718	22,499	45,690	39,368
Net investment and Interest income	30,509	36,780	64,082	71,779
Other revenue	167,429	142,578	303,501	248,757
Total revenues	1,702,864	1,664,254	3,300,704	3,137,110
Costs and expenses:
Operating expenses	811,594	696,074	1,544,761	1,310,603
Commission expenses	125,341	127,896	243,834	241,045
Cost of sales	72,625	66,491	152,296	136,406
Benefits and losses	37,363	44,630	81,463	91,928
Amortization of deferred policy acquisition costs	6,972	6,750	14,644	15,573
Lease expense	7,684	7,441	15,159	15,088
Depreciation, net of (gains) losses on disposals	117,318	135,748	231,114	257,465
Net (gains) losses on disposal of real estate	1,872	523	4,179	(3,907)
Total costs and expenses	1,180,769	1,085,553	2,287,450	2,064,201
Earnings (loss) from operations before equity in earnings of subsidiaries	522,095	578,701	1,013,254	1,072,909
Equity in earnings of subsidiaries	0	0	0	0
Earnings from operations	522,095	578,701	1,013,254	1,072,909
Fees and amortization on early extinguishment of debt	(959)	0	(959)	0
Other components of net periodic benefit costs	(304)	(280)	(608)	(560)
Interest expense	(57,193)	(39,545)	(106,992)	(78,723)
Pretax earnings	463,639	538,876	904,695	993,626
Income tax expense	(111,624)	(128,978)	(218,678)	(238,553)
Earnings available to common stockholders	352,015	409,898	686,017	755,073
Operating Segments [Member] | Moving and Storage Consolidations [Member]
Revenues:
Self-moving equipment rentals	1,163,376	1,180,329	2,255,086	2,216,542
Self-storage revenues	185,586	153,485	358,763	290,878
Self moving and self-storage products and service sales	96,864	92,191	206,215	197,076
Property management fees	9,277	8,747	18,416	17,196
Life insurance premiums	0	0	0	0
Property and casualty insurance premiums	0	0	0	0
Net investment and Interest income	15,077	675	20,017	1,355
Other revenue	166,678	141,572	301,959	247,206
Total revenues	1,636,858	1,576,999	3,160,456	2,970,253
Costs and expenses:
Operating expenses	796,498	682,329	1,516,292	1,284,160
Commission expenses	125,341	127,896	243,834	241,045
Cost of sales	72,625	66,491	152,296	136,406
Benefits and losses	0	0	0	0
Amortization of deferred policy acquisition costs	0	0	0	0
Lease expense	8,261	8,024	16,181	16,101
Depreciation, net of (gains) losses on disposals	117,318	135,748	231,114	257,465
Net (gains) losses on disposal of real estate	1,872	523	4,179	(3,907)
Total costs and expenses	1,121,915	1,021,011	2,163,896	1,931,270
Earnings (loss) from operations before equity in earnings of subsidiaries	514,943	555,988	996,560	1,038,983
Equity in earnings of subsidiaries	6,055	18,289	13,721	27,408
Earnings from operations	520,998	574,277	1,010,281	1,066,391
Fees and amortization on early extinguishment of debt	(959)		(959)
Other components of net periodic benefit costs	(304)	(280)	(608)	(560)
Interest expense	(57,459)	(39,814)	(107,520)	(79,257)
Pretax earnings	462,276	534,183	901,194	986,574
Income tax expense	(110,261)	(124,285)	(215,177)	(231,501)
Earnings available to common stockholders	352,015	409,898	686,017	755,073
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	25,960	23,357	46,790	40,800
Net investment and Interest income	(2,597)	6,182	(345)	12,195
Other revenue	0	0	0	0
Total revenues	23,363	29,539	46,445	52,995
Costs and expenses:
Operating expenses	11,576	10,768	21,770	19,581
Commission expenses	0	0	0	0
Cost of sales	0	0	0	0
Benefits and losses	6,075	3,560	10,454	8,787
Amortization of deferred policy acquisition costs	0	0	0	0
Lease expense	26	22	184	206
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	17,677	14,350	32,408	28,574
Earnings (loss) from operations before equity in earnings of subsidiaries	5,686	15,189	14,037	24,421
Equity in earnings of subsidiaries	0	0	0	0
Earnings from operations	5,686	15,189	14,037	24,421
Fees and amortization on early extinguishment of debt	0		0
Other components of net periodic benefit costs	0	0	0	0
Interest expense	0	0	0	0
Pretax earnings	5,686	15,189	14,037	24,421
Income tax expense	(1,167)	(3,176)	(2,922)	(5,106)
Earnings available to common stockholders	4,519	12,013	11,115	19,315
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	25,456	28,913	51,237	57,618
Property and casualty insurance premiums	0	0	0	0
Net investment and Interest income	19,041	30,942	46,429	60,266
Other revenue	1,199	1,130	2,133	1,760
Total revenues	45,696	60,985	99,799	119,644
Costs and expenses:
Operating expenses	5,558	5,223	10,667	10,598
Commission expenses	0	0	0	0
Cost of sales	0	0	0	0
Benefits and losses	31,288	41,070	71,009	83,141
Amortization of deferred policy acquisition costs	6,972	6,750	14,644	15,573
Lease expense	26	29	54	53
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	43,844	53,072	96,374	109,365
Earnings (loss) from operations before equity in earnings of subsidiaries	1,852	7,913	3,425	10,279
Equity in earnings of subsidiaries	0	0	0	0
Earnings from operations	1,852	7,913	3,425	10,279
Fees and amortization on early extinguishment of debt	0		0
Other components of net periodic benefit costs	0	0	0	0
Interest expense	(120)	(120)	(240)	(240)
Pretax earnings	1,732	7,793	3,185	10,039
Income tax expense	(196)	(1,517)	(579)	(1,946)
Earnings available to common stockholders	1,536	6,276	2,606	8,093
Consolidation, Eliminations [Member]
Revenues:
Self-moving equipment rentals	(1,351)	(1,268)	(2,286)	(2,104)
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	(242)	(858)	(1,100)	(1,432)
Net investment and Interest income	(1,012)	(1,019)	(2,019)	(2,037)
Other revenue	(448)	(124)	(591)	(209)
Total revenues	(3,053)	(3,269)	(5,996)	(5,782)
Costs and expenses:
Operating expenses	(2,038)	(2,246)	(3,968)	(3,736)
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)	(634)	(1,260)	(1,272)
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	(2,667)	(2,880)	(5,228)	(5,008)
Earnings (loss) from operations before equity in earnings of subsidiaries	(386)	(389)	(768)	(774)
Equity in earnings of subsidiaries	(6,055)	(18,289)	(13,721)	(27,408)
Earnings from operations	(6,441)	(18,678)	(14,489)	(28,182)
Fees and amortization on early extinguishment of debt	0		0
Other components of net periodic benefit costs	0	0	0	0
Interest expense	386	389	768	774
Pretax earnings	(6,055)	(18,289)	(13,721)	(27,408)
Income tax expense	0	0	0	0
Earnings available to common stockholders	$ (6,055)	$ (18,289)	$ (13,721)	$ (27,408)