Consolidating financial information by industry segment (Statements of Operations) (Details) - USD ($) $ in Thousands	3 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Revenues:
Self-moving equipment rentals	$ 654,285	$ 748,596
Self-storage revenues	108,955	98,274
Self moving and self-storage products and service sales	91,350	80,026
Property management fees	7,347	7,156
Life insurance premiums	30,908	32,710
Property and casualty insurance premiums	13,734	13,424
Investment income interest and dividend	16,982	35,749
Other revenue	63,676	63,314
Total revenues	987,237	1,079,249
Costs and expenses:
Operating expenses	492,662	534,472
Commission expenses	69,175	80,899
Cost of sales	52,831	48,929
Benefits and losses	39,577	49,006
Amortization of deferred policy acquisition costs	6,888	6,064
Lease expense	6,603	7,036
Depreciation, net of (gains) losses on disposals	165,671	140,600
Net (gains) losses on disposal of real estate	(256)	(1,622)
Total costs and expenses	833,151	865,384
Earnings (loss) from operations before equity in earnings of subsidiaries	154,086	213,865
Equity in earnings of subsidiaries	0	0
Earnings from operations	154,086	213,865
Other components of net periodic benefit costs	(247)	(263)
Interest expense	(39,521)	(38,888)
Pretax earnings	114,318	174,714
Income tax expense	(26,592)	(42,292)
Earnings available to common stockholders	87,726	132,422
Operating Segments [Member] | Moving and Storage Consolidations [Member]
Revenues:
Self-moving equipment rentals	654,913	749,136
Self-storage revenues	108,955	98,274
Self moving and self-storage products and service sales	91,350	80,026
Property management fees	7,347	7,156
Life insurance premiums	0	0
Property and casualty insurance premiums	0	0
Investment income interest and dividend	662	3,267
Other revenue	63,073	62,539
Total revenues	926,300	1,000,398
Costs and expenses:
Operating expenses	480,081	522,524
Commission expenses	69,175	80,899
Cost of sales	52,831	48,929
Benefits and losses	0	0
Amortization of deferred policy acquisition costs	0	0
Lease expense	7,137	7,172
Depreciation, net of (gains) losses on disposals	165,671	140,600
Net (gains) losses on disposal of real estate	(256)	(1,622)
Total costs and expenses	774,639	798,502
Earnings (loss) from operations before equity in earnings of subsidiaries	151,661	201,896
Equity in earnings of subsidiaries	2,395	9,831
Earnings from operations	154,056	211,727
Other components of net periodic benefit costs	(247)	(263)
Interest expense	(39,794)	(39,166)
Pretax earnings	114,015	172,298
Income tax expense	(26,289)	(39,876)
Earnings available to common stockholders	87,726	132,422
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	14,507	14,114
Investment income interest and dividend	(873)	6,191
Other revenue	0	0
Total revenues	13,634	20,305
Costs and expenses:
Operating expenses	8,825	8,081
Commission expenses	0	0
Cost of sales	0	0
Benefits and losses	4,030	3,758
Amortization of deferred policy acquisition costs	0	0
Lease expense	1	0
Depreciation, net of (gains) losses on disposals	0	0
Net (gains) losses on disposal of real estate	0	0
Total costs and expenses	12,856	11,839
Earnings (loss) from operations before equity in earnings of subsidiaries	778	8,466
Equity in earnings of subsidiaries	0	0
Earnings from operations	778	8,466
Other components of net periodic benefit costs	0	0
Interest expense	0	0
Pretax earnings	778	8,466
Income tax expense	(162)	(1,778)
Earnings available to common stockholders	616	6,688
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	30,908	32,710
Property and casualty insurance premiums	0	0
Investment income interest and dividend	18,006	26,701
Other revenue	739	910
Total revenues	49,653	60,321
Costs and expenses:
Operating expenses	5,288	5,228
Commission expenses	0	0
Cost of sales	0	0
Benefits and losses	35,547	45,248
Amortization of deferred policy acquisition costs	6,888	6,064
Lease expense	10	0
Depreciation, net of (gains) losses on disposals	0	0
Net (gains) losses on disposal of real estate	0	0
Total costs and expenses	47,733	56,540
Earnings (loss) from operations before equity in earnings of subsidiaries	1,920	3,781
Equity in earnings of subsidiaries	0	0
Earnings from operations	1,920	3,781
Other components of net periodic benefit costs	0	0
Interest expense	0	0
Pretax earnings	1,920	3,781
Income tax expense	(141)	(638)
Earnings available to common stockholders	1,779	3,143
Consolidation, Eliminations [Member]
Revenues:
Self-moving equipment rentals	(628)	(540)
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	(773)	(690)
Investment income interest and dividend	(813)	(410)
Other revenue	(136)	(135)
Total revenues	(2,350)	(1,775)
Costs and expenses:
Operating expenses	(1,532)	(1,361)
Commission expenses	0	0
Cost of sales	0	0
Benefits and losses	0	0
Amortization of deferred policy acquisition costs	0	0
Lease expense	(545)	(136)
Depreciation, net of (gains) losses on disposals	0	0
Net (gains) losses on disposal of real estate	0	0
Total costs and expenses	(2,077)	(1,497)
Earnings (loss) from operations before equity in earnings of subsidiaries	(273)	(278)
Equity in earnings of subsidiaries	(2,395)	(9,831)
Earnings from operations	(2,668)	(10,109)
Other components of net periodic benefit costs	0	0
Interest expense	273	278
Pretax earnings	(2,395)	(9,831)
Income tax expense	0	0
Earnings available to common stockholders	$ (2,395)	$ (9,831)