Consolidating financial information by industry segment (Statements of Operations) (Details) - USD ($) $ in Thousands		3 Months Ended
		Jun. 30, 2016		Jun. 30, 2015
Revenues:
Self-moving equipment rentals		$ 646,336		$ 629,286
Self-storage revenues		67,722		57,191
Self-moving and self-storage products and service sales		77,303		77,258
Property management fees		6,604		6,111
Life insurance premiums		40,892		40,266
Property and casualty insurance premiums		11,255		10,556
Net investment and interest income		27,549		21,972
Other revenue		45,748		42,165
Total revenues		923,409		884,805
Costs and expenses:
Operating expenses		385,082		363,169
Commission expenses		73,816		73,058
Cost of sales		43,362		41,255
Benefits and losses		47,003		43,391
Amortization of deferred policy acquisition costs		7,942		4,778
Lease expense		11,048		17,064
Depreciation, net of (gains) losses on disposals		95,381		50,982
Total costs and expenses		663,634		593,697
Earnings (loss) from operations before equity in earnings of subsidiaries		259,775		291,108
Equity in earnings of subsidiaries
Earnings from operations		259,775		291,108
Interest expense		(26,644)		(22,100)
Pretax earnings		233,131		269,008
Income tax expense		(85,958)		(97,723)
Earnings available to common shareholders		147,173		171,285
Operating Segments [Member] | Moving and Storage Consolidations [Member]
Revenues:
Self-moving equipment rentals		647,116		630,039
Self-storage revenues		67,722		57,191
Self-moving and self-storage products and service sales		77,303		77,258
Property management fees		6,604		6,111
Life insurance premiums
Property and casualty insurance premiums
Net investment and interest income		2,112		2,817
Other revenue		44,974		41,424
Total revenues		845,831		814,840
Costs and expenses:
Operating expenses		373,672		351,855
Commission expenses		73,816		73,058
Cost of sales		43,362		41,255
Benefits and losses
Amortization of deferred policy acquisition costs
Lease expense		11,095		17,111
Depreciation, net of (gains) losses on disposals		95,381		50,982
Total costs and expenses		597,326		534,261
Earnings (loss) from operations before equity in earnings of subsidiaries		248,505		280,579
Equity in earnings of subsidiaries		7,574		6,950
Earnings from operations		256,079		287,529
Interest expense		(26,793)		(22,260)
Pretax earnings		229,286		265,269
Income tax expense		(82,113)		(93,984)
Earnings available to common shareholders		147,173		171,285
Operating Segments [Member] | Property and Casualty Insurance [Member]
Revenues:
Self-moving equipment rentals			[1]		[2]
Self-storage revenues			[1]		[2]
Self-moving and self-storage products and service sales			[1]		[2]
Property management fees			[1]		[2]
Life insurance premiums			[1]		[2]
Property and casualty insurance premiums		11,255	[1]	10,556	[2]
Net investment and interest income		5,630	[1]	4,334	[2]
Other revenue			[1]		[2]
Total revenues		16,885	[1]	14,890	[2]
Costs and expenses:
Operating expenses		6,285	[1]	6,339	[2]
Commission expenses			[1]		[2]
Cost of sales			[1]		[2]
Benefits and losses		3,097	[1]	2,073	[2]
Amortization of deferred policy acquisition costs			[1]		[2]
Lease expense			[1]		[2]
Depreciation, net of (gains) losses on disposals			[1]		[2]
Total costs and expenses		9,382	[1]	8,412	[2]
Earnings (loss) from operations before equity in earnings of subsidiaries		7,503	[1]	6,478	[2]
Equity in earnings of subsidiaries			[1]		[2]
Earnings from operations		7,503	[1]	6,478	[2]
Interest expense			[1]		[2]
Pretax earnings		7,503	[1]	6,478	[2]
Income tax expense		(2,626)	[1]	(2,267)	[2]
Earnings available to common shareholders		4,877	[1]	4,211	[2]
Operating Segments [Member] | Life Insurance [Member]
Revenues:
Self-moving equipment rentals			[1]		[2]
Self-storage revenues			[1]		[2]
Self-moving and self-storage products and service sales			[1]		[2]
Property management fees			[1]		[2]
Life insurance premiums		40,892	[1]	40,266	[2]
Property and casualty insurance premiums			[1]		[2]
Net investment and interest income		19,994	[1]	15,020	[2]
Other revenue		909	[1]	783	[2]
Total revenues		61,795	[1]	56,069	[2]
Costs and expenses:
Operating expenses		6,031	[1]	5,762	[2]
Commission expenses			[1]		[2]
Cost of sales			[1]		[2]
Benefits and losses		43,906	[1]	41,318	[2]
Amortization of deferred policy acquisition costs		7,942	[1]	4,778	[2]
Lease expense			[1]		[2]
Depreciation, net of (gains) losses on disposals			[1]		[2]
Total costs and expenses		57,879	[1]	51,858	[2]
Earnings (loss) from operations before equity in earnings of subsidiaries		3,916	[1]	4,211	[2]
Equity in earnings of subsidiaries			[1]		[2]
Earnings from operations		3,916	[1]	4,211	[2]
Interest expense			[1]		[2]
Pretax earnings		3,916	[1]	4,211	[2]
Income tax expense		(1,219)	[1]	(1,472)	[2]
Earnings available to common shareholders		2,697	[1]	2,739	[2]
Consolidation, Eliminations [Member]
Revenues:
Self-moving equipment rentals	[3]	(780)		(753)
Self-storage revenues
Self-moving and self-storage products and service sales
Property management fees
Life insurance premiums
Property and casualty insurance premiums
Net investment and interest income	[4]	(187)		(199)
Other revenue	[4]	(135)		(42)
Total revenues		(1,102)		(994)
Costs and expenses:
Operating expenses	[3],[4]	(906)		(787)
Commission expenses
Cost of sales
Benefits and losses
Amortization of deferred policy acquisition costs
Lease expense	[4]	(47)		(47)
Depreciation, net of (gains) losses on disposals
Total costs and expenses		(953)		(834)
Earnings (loss) from operations before equity in earnings of subsidiaries		(149)		(160)
Equity in earnings of subsidiaries	[5]	(7,574)		(6,950)
Earnings from operations		(7,723)		(7,110)
Interest expense	[4]	149		160
Pretax earnings		(7,574)		(6,950)
Income tax expense
Earnings available to common shareholders		$ (7,574)		$ (6,950)

[1] Balances for the quarter ended March 31, 2016

[2] Balances for the quarter ended March 31, 2015

[3] Eliminate intercompany premiums

[4] Eliminate intercompany lease / interest income

[5] Eliminate equity in earnings of subsidiaries