Consolidating financial information by industry segment (Statements of Operations) (Details) - USD ($) $ in Thousands		3 Months Ended
		Jun. 30, 2017		Jun. 30, 2016
Revenues:
Self-moving equipment rentals		$ 669,858		$ 646,336
Self-storage revenues		76,718		67,722
Self-moving and self-storage products and service sales		78,911		77,303
Property management fees		6,762		6,604
Life insurance premiums		39,091		40,892
Property and casualty insurance premiums		11,815		11,255
Net investment and interest income		27,217		27,331
Other revenue		47,553		45,748
Total revenues		957,925		923,191
Costs and expenses:
Operating expenses		416,924		385,082
Commission expenses		75,365		73,816
Cost of sales		47,595		43,362
Benefits and losses		47,720		47,003
Amortization of deferred policy acquisition costs		6,321		7,942
Lease expense		8,287		11,048
Depreciation, net of (gains) losses on disposals		126,682		95,381
Total costs and expenses		728,894		663,634
Earnings (loss) from operations before equity in earnings of subsidiaries		229,031		259,557
Equity in earnings of subsidiaries
Earnings from operations		229,031		259,557
Interest expense		(30,345)		(26,426)
Pretax earnings		198,686		233,131
Income tax expense		(72,479)		(85,958)
Earnings available to common stockholders		126,207		147,173
Operating Segments [Member] | Moving and Storage Consolidations [Member]
Revenues:
Self-moving equipment rentals		670,698		647,116
Self-storage revenues		76,718		67,722
Self-moving and self-storage products and service sales		78,911		77,303
Property management fees		6,762		6,604
Life insurance premiums
Property and casualty insurance premiums
Net investment and interest income		2,657		2,112
Other revenue		46,781		44,974
Total revenues		882,527		845,831
Costs and expenses:
Operating expenses		404,043		373,672
Commission expenses		75,365		73,816
Cost of sales		47,595		43,362
Benefits and losses
Amortization of deferred policy acquisition costs
Lease expense		8,334		11,095
Depreciation, net of (gains) losses on disposals		126,682		95,381
Total costs and expenses		662,019		597,326
Earnings (loss) from operations before equity in earnings of subsidiaries		220,508		248,505
Equity in earnings of subsidiaries		5,810		7,574
Earnings from operations		226,318		256,079
Interest expense		(30,694)		(26,793)
Pretax earnings		195,624		229,286
Income tax expense		(69,417)		(82,113)
Earnings available to common stockholders		126,207		147,173
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		11,815	[1]	11,255	[2]
Net investment and interest income		4,291	[1]	5,630	[2]
Other revenue			[1]		[2]
Total revenues		16,106	[1]	16,885	[2]
Costs and expenses:
Operating expenses		8,232	[1]	6,285	[2]
Commission expenses			[1]		[2]
Cost of sales			[1]		[2]
Benefits and losses		2,438	[1]	3,097	[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		10,670	[1]	9,382	[2]
Earnings (loss) from operations before equity in earnings of subsidiaries		5,436	[1]	7,503	[2]
Equity in earnings of subsidiaries			[1]		[2]
Earnings from operations		5,436	[1]	7,503	[2]
Interest expense			[1]		[2]
Pretax earnings		5,436	[1]	7,503	[2]
Income tax expense		(1,862)	[1]	(2,626)	[2]
Earnings available to common stockholders		3,574		4,877
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		39,091	[1]	40,892	[2]
Property and casualty insurance premiums			[1]		[2]
Net investment and interest income		20,655	[1]	19,994	[2]
Other revenue		910	[1]	909	[2]
Total revenues		60,656	[1]	61,795	[2]
Costs and expenses:
Operating expenses		5,617	[1]	6,031	[2]
Commission expenses			[1]		[2]
Cost of sales			[1]		[2]
Benefits and losses		45,282	[1]	43,906	[2]
Amortization of deferred policy acquisition costs		6,321	[1]	7,942	[2]
Lease expense			[1]		[2]
Depreciation, net of (gains) losses on disposals			[1]		[2]
Total costs and expenses		57,220	[1]	57,879	[2]
Earnings (loss) from operations before equity in earnings of subsidiaries		3,436	[1]	3,916	[2]
Equity in earnings of subsidiaries			[1]		[2]
Earnings from operations		3,436	[1]	3,916	[2]
Interest expense			[1]		[2]
Pretax earnings		3,436	[1]	3,916	[2]
Income tax expense		(1,200)	[1]	(1,219)	[2]
Earnings available to common stockholders		2,236		2,697
Consolidation, Eliminations [Member]
Revenues:
Self-moving equipment rentals	[3]	(840)		(780)
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]	(386)		(405)
Other revenue	[4]	(138)		(135)
Total revenues		(1,364)		(1,320)
Costs and expenses:
Operating expenses	[3],[4]	(968)		(906)
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		(1,015)		(953)
Earnings (loss) from operations before equity in earnings of subsidiaries		(349)		(367)
Equity in earnings of subsidiaries	[5]	(5,810)		(7,574)
Earnings from operations		(6,159)		(7,941)
Interest expense	[4]	349		367
Pretax earnings		(5,810)		(7,574)
Income tax expense
Earnings available to common stockholders		$ (5,810)		$ (7,574)

[1] Balances for the quarter ended March 31, 2017

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

[3] Eliminate intercompany premiums

[4] Eliminate intercompany lease / interest income

[5] Eliminate equity in earnings of subsidiaries