Consolidating financial information by industry segment (Statements of Operations) (Details) - USD ($) $ in Thousands		3 Months Ended				9 Months Ended
		Dec. 31, 2015		Dec. 31, 2014		Dec. 31, 2015		Dec. 31, 2014
Revenues:
Self-moving equipment rentals		$ 517,403		$ 487,415		$ 1,844,908		$ 1,716,424
Self-storage revenues		63,164		53,503		182,415		155,623
Self-moving and self-storage products and service sales		50,038		49,081		197,999		191,603
Property management fees		8,170		7,497		20,601		18,970
Life insurance premiums		40,657		39,026		121,438		115,997
Property and casualty insurance premiums		14,105		13,584		38,033		35,665
Net investment and interest income		19,026		20,752		63,149		63,654
Other revenue		32,188		35,497		123,916		133,865
Total revenues		744,751		706,355		2,592,459		2,431,801
Costs and expenses:
Operating expenses		356,156		338,692		1,125,607		1,085,961
Commission expenses		58,347		58,439		212,204		200,939
Cost of sales		29,460		30,751		110,596		112,215
Benefits and losses		41,574		40,084		128,393		120,426
Amortization of deferred policy acquisition costs		5,138		4,722		15,559		13,196
Lease expense		10,461		18,705		40,249		60,950
Depreciation, net of (gains) losses on disposals		85,713		81,810		199,773		209,927
Total costs and expenses		586,849		573,203		1,832,381		1,803,614
Earnings (loss) from operations before equity in earnings of subsidiaries		157,902		$ 133,152		760,078		628,187
Equity in earnings of subsidiaries
Earnings from operations		157,902		$ 133,152		760,078		628,187
Interest expense		(25,407)		(25,719)		$ (71,480)		(74,744)
Fees and amortization on early extinguishment of debt								(4,081)
Pretax earnings		132,495		107,433		$ 688,598		549,362
Income tax expense		(50,726)		(40,893)		(252,165)		(202,101)
Earnings available to common shareholders		81,769		66,540		436,433		347,261
Operating Segments [Member] | Moving and Storage Consolidations [Member]
Revenues:
Self-moving equipment rentals		518,438		488,505		1,847,661		1,719,200
Self-storage revenues		63,164		53,503		182,415		155,623
Self-moving and self-storage products and service sales		50,038		49,081		197,999		191,603
Property management fees		$ 8,170		$ 7,497		$ 20,601		$ 18,970
Life insurance premiums
Property and casualty insurance premiums
Net investment and interest income		$ 1,976		$ 2,838		$ 6,638		$ 10,785
Other revenue		30,966		34,409		120,572		130,718
Total revenues		672,752		635,833		2,375,886		2,226,899
Costs and expenses:
Operating expenses		344,654		328,187		1,091,169		1,053,584
Commission expenses		58,347		58,439		212,204		200,939
Cost of sales		$ 29,460		$ 30,751		$ 110,596		$ 112,215
Benefits and losses
Amortization of deferred policy acquisition costs
Lease expense		$ 10,508		$ 18,755		$ 40,389		$ 61,090
Depreciation, net of (gains) losses on disposals		85,713		81,810		199,773		209,927
Total costs and expenses		528,682		517,942		1,654,131		1,637,755
Earnings (loss) from operations before equity in earnings of subsidiaries		144,070		117,891		721,755		589,144
Equity in earnings of subsidiaries		9,090		10,088		25,219		25,763
Earnings from operations		153,160		127,979		746,974		614,907
Interest expense		(25,564)		(25,875)		(71,957)		(75,218)
Fees and amortization on early extinguishment of debt								(4,081)
Pretax earnings		127,596		102,104		675,017		535,608
Income tax expense		(45,827)		(35,564)		(238,584)		(188,347)
Earnings available to common shareholders		$ 81,769		$ 66,540		$ 436,433		$ 347,261
Operating Segments [Member] | Property and Casualty Insurance [Member]
Revenues:
Self-moving equipment rentals			[1]		[2]		[3]		[4]
Self-storage revenues			[1]		[2]		[3]		[4]
Self-moving and self-storage products and service sales			[1]		[2]		[3]		[4]
Property management fees			[1]		[2]		[3]		[4]
Life insurance premiums			[1]		[2]		[3]		[4]
Property and casualty insurance premiums		$ 14,105	[1]	$ 13,584	[2]	$ 38,033	[3]	$ 35,665	[4]
Net investment and interest income		$ 3,252	[1]	$ 2,961	[2]	$ 10,839	[3]	$ 9,823	[4]
Other revenue			[1]		[2]		[3]		[4]
Total revenues		$ 17,357	[1]	$ 16,545	[2]	$ 48,872	[3]	$ 45,488	[4]
Costs and expenses:
Operating expenses		$ 7,048	[1]	$ 6,123	[2]	$ 20,476	[3]	$ 18,635	[4]
Commission expenses			[1]		[2]		[3]		[4]
Cost of sales			[1]		[2]		[3]		[4]
Benefits and losses		$ 4,038	[1]	$ 3,481	[2]	$ 9,582	[3]	$ 8,918	[4]
Amortization of deferred policy acquisition costs			[1]		[2]		[3]		[4]
Lease expense			[1]		[2]		[3]		[4]
Depreciation, net of (gains) losses on disposals			[1]		[2]		[3]		[4]
Total costs and expenses		$ 11,086	[1]	$ 9,604	[2]	$ 30,058	[3]	$ 27,553	[4]
Earnings (loss) from operations before equity in earnings of subsidiaries		$ 6,271	[1]	$ 6,941	[2]	$ 18,814	[3]	$ 17,935	[4]
Equity in earnings of subsidiaries			[1]		[2]		[3]		[4]
Earnings from operations		$ 6,271	[1]	$ 6,941	[2]	$ 18,814	[3]	$ 17,935	[4]
Interest expense			[1]		[2]		[3]		[4]
Fees and amortization on early extinguishment of debt	[4]
Pretax earnings		$ 6,271	[1]	$ 6,941	[2]	$ 18,814	[3]	$ 17,935	[4]
Income tax expense		(2,195)	[1]	(2,428)	[2]	(6,585)	[3]	(6,277)	[4]
Earnings available to common shareholders		$ 4,076	[1]	$ 4,513	[2]	$ 12,229	[5]	$ 11,658	[6]
Operating Segments [Member] | Life Insurance [Member]
Revenues:
Self-moving equipment rentals			[1]		[2]		[3]		[4]
Self-storage revenues			[1]		[2]		[3]		[4]
Self-moving and self-storage products and service sales			[1]		[2]		[3]		[4]
Property management fees			[1]		[2]		[3]		[4]
Life insurance premiums		$ 40,657	[1]	$ 39,026	[2]	$ 121,438	[3]	$ 115,997	[4]
Property and casualty insurance premiums			[1]		[2]		[3]		[4]
Net investment and interest income		$ 13,993	[1]	$ 15,149	[2]	$ 46,261	[3]	$ 43,632	[4]
Other revenue		1,498	[1]	1,202	[2]	3,705	[3]	3,491	[4]
Total revenues		56,148	[1]	55,377	[2]	171,404	[3]	163,120	[4]
Costs and expenses:
Operating expenses		$ 5,756	[1]	$ 5,576	[2]	$ 17,048	[3]	$ 16,834	[4]
Commission expenses			[1]		[2]		[3]		[4]
Cost of sales			[1]		[2]		[3]		[4]
Benefits and losses		$ 37,536	[1]	$ 36,603	[2]	$ 118,811	[3]	$ 111,508	[4]
Amortization of deferred policy acquisition costs		$ 5,138	[1]	$ 4,722	[2]	$ 15,559	[3]	$ 13,196	[4]
Lease expense			[1]		[2]		[3]		[4]
Depreciation, net of (gains) losses on disposals			[1]		[2]		[3]		[4]
Total costs and expenses		$ 48,430	[1]	$ 46,901	[2]	$ 151,418	[3]	$ 141,538	[4]
Earnings (loss) from operations before equity in earnings of subsidiaries		$ 7,718	[1]	$ 8,476	[2]	$ 19,986	[3]	$ 21,582	[4]
Equity in earnings of subsidiaries			[1]		[2]		[3]		[4]
Earnings from operations		$ 7,718	[1]	$ 8,476	[2]	$ 19,986	[3]	$ 21,582	[4]
Interest expense			[1]		[2]		[3]		[4]
Fees and amortization on early extinguishment of debt	[4]
Pretax earnings		$ 7,718	[1]	$ 8,476	[2]	$ 19,986	[3]	$ 21,582	[4]
Income tax expense		(2,704)	[1]	(2,901)	[2]	(6,996)	[3]	(7,477)	[4]
Earnings available to common shareholders		5,014	[1]	5,575	[2]	12,990	[5]	14,105	[6]
Consolidation, Eliminations [Member]
Revenues:
Self-moving equipment rentals	[7]	$ (1,035)		$ (1,090)		$ (2,753)		$ (2,776)
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	[8]	$ (195)		$ (196)		$ (589)		$ (586)
Other revenue	[8]	(276)		(114)		(361)		(344)
Total revenues		(1,506)		(1,400)		(3,703)		(3,706)
Costs and expenses:
Operating expenses	[7],[8]	$ (1,302)		$ (1,194)		$ (3,086)		$ (3,092)
Commission expenses
Cost of sales
Benefits and losses
Amortization of deferred policy acquisition costs
Lease expense	[8]	$ (47)		$ (50)		$ (140)		$ (140)
Depreciation, net of (gains) losses on disposals
Total costs and expenses		$ (1,349)		$ (1,244)		$ (3,226)		$ (3,232)
Earnings (loss) from operations before equity in earnings of subsidiaries		(157)		(156)		(477)		(474)
Equity in earnings of subsidiaries	[9]	(9,090)		(10,088)		(25,219)		(25,763)
Earnings from operations		(9,247)		(10,244)		(25,696)		(26,237)
Interest expense	[8]	157		156		477		$ 474
Fees and amortization on early extinguishment of debt
Pretax earnings		$ (9,090)		$ (10,088)		$ (25,219)		$ (25,763)
Income tax expense
Earnings available to common shareholders		$ (9,090)		$ (10,088)		$ (25,219)		$ (25,763)

[1] Balances for the quarter ended September 30, 2015

[2] Balances for the quarter ended September 30, 2014

[3] Balances for the nine months ended September 30, 2015

[4] Balances for the nine months ended September 30, 2014

[5] Balance for the period ended September 30, 2015

[6] Balance for the period ended September 30, 2014

[7] Eliminate intercompany premiums

[8] Eliminate intercompany lease / interest income

[9] Eliminate equity in earnings of subsidiaries