Consolidating financial information by industry segment (Statements of Operations) (Details) - USD ($) $ in Thousands		3 Months Ended				9 Months Ended
		Dec. 31, 2018		Dec. 31, 2017		Dec. 31, 2018		Dec. 31, 2017
Revenues:
Self-moving equipment rentals		$ 626,136		$ 574,801		$ 2,124,451		$ 1,985,217
Self-storage revenues		93,392		82,127		271,097		239,317
Self-moving and self-storage products and service sales		55,665		53,130		207,819		205,309
Property management fees		7,899		9,881		22,507		23,474
Life insurance premiums		34,778		38,957		107,586		116,910
Property and casualty insurance premiums		17,668		16,093		46,732		42,934
Net investment and interest income		32,211		28,821		85,043		82,507
Other revenue		51,342		39,072		177,940		147,825
Total revenues		919,091		842,882		3,043,175		2,843,493
Costs and expenses:
Operating expenses		478,461		437,840		1,504,365		1,346,782
Commission expenses		67,493		63,487		232,084		222,203
Cost of sales		34,149		33,995		130,432		124,456
Benefits and losses		42,869		45,168		137,196		139,997
Amortization of deferred policy acquisition costs		6,654		5,952		18,584		18,217
Lease expense		7,890		8,415		24,229		25,277
Depreciation, net of (gains) losses on disposals		143,473		137,061		402,525		396,540
Net gains on disposal of real estate				(192,404)		10		(192,223)
Total costs and expenses		780,989		539,514		2,449,425		2,081,249
Earnings (loss) from operations before equity in earnings of subsidiaries		138,102		303,368		593,750		762,244
Equity in earnings of subsidiaries
Earnings from operations		138,102		303,368		593,750		762,244
Other components of net periodic benefit recovery costs		253		231		760		695
Interest expense		(34,827)		(31,558)		(105,111)		(93,926)
Pretax earnings		103,022		271,579		487,879		667,623
Income tax (expense) benefit		(24,387)		257,315		(117,853)		112,117
Earnings available to common shareholders		78,635		528,894		370,026		779,740
Operating Segments [Member] | Moving and Storage Consolidations [Member]
Revenues:
Self-moving equipment rentals		627,543		576,018		2,128,120		1,988,430
Self-storage revenues		93,392		82,127		271,097		239,317
Self-moving and self-storage products and service sales		55,665		53,130		207,819		205,309
Property management fees		7,899		9,881		22,507		23,474
Life insurance premiums
Property and casualty insurance premiums
Net investment and interest income		4,364		3,662		9,757		9,496
Other revenue		50,065		37,669		174,447		144,196
Total revenues		838,928		762,487		2,813,747		2,610,222
Costs and expenses:
Operating expenses		465,828		426,163		1,467,831		1,310,194
Commission expenses		67,493		63,487		232,084		222,203
Cost of sales		34,149		33,995		130,432		124,456
Benefits and losses
Amortization of deferred policy acquisition costs
Lease expense		8,026		8,498		24,637		25,460
Depreciation, net of (gains) losses on disposals		143,473		137,061		402,525		396,540
Net gains on disposal of real estate				(192,404)		10		(192,223)
Total costs and expenses		718,969		476,800		2,257,519		1,886,633
Earnings (loss) from operations before equity in earnings of subsidiaries		119,959		285,687		556,228		723,589
Equity in earnings of subsidiaries		14,664		11,823		30,306		25,998
Earnings from operations		134,623		297,510		586,534		749,587
Other components of net periodic benefit recovery costs		(253)		(231)		(760)		(695)
Interest expense		(35,114)		(31,854)		(105,974)		(94,925)
Pretax earnings		99,256		265,425		479,800		653,967
Income tax (expense) benefit		(20,621)		263,469		(109,774)		125,773
Earnings available to common shareholders		78,635		528,894		370,026		779,740
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		18,128	[1]	16,754	[2]	48,448	[3]	44,067	[4]
Net investment and interest income		4,018	[1]	3,645	[2]	10,109	[3]	11,637	[4]
Other revenue			[1]		[2]		[3]		[4]
Total revenues		22,146	[1]	20,399	[2]	58,557	[3]	55,704	[4]
Costs and expenses:
Operating expenses		9,412	[1]	8,160	[2]	26,027	[3]	24,632	[4]
Commission expenses			[1]		[2]		[3]		[4]
Cost of sales			[1]		[2]		[3]		[4]
Benefits and losses		1,733	[1]	4,644	[2]	10,957	[3]	11,954	[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]
Net gains on disposal of real estate			[1]		[2]		[3]		[4]
Total costs and expenses		11,145	[1]	12,804	[2]	36,984	[3]	36,586	[4]
Earnings (loss) from operations before equity in earnings of subsidiaries		11,001	[1]	7,595	[2]	21,573	[3]	19,118	[4]
Equity in earnings of subsidiaries			[1]		[2]		[3]		[4]
Earnings from operations		11,001	[1]	7,595	[2]	21,573	[3]	19,118	[4]
Other components of net periodic benefit recovery costs			[1]		[2]		[3]		[4]
Interest expense			[1]		[2]		[3]		[4]
Pretax earnings		11,001	[1]	7,595	[2]	21,573	[3]	19,118	[4]
Income tax (expense) benefit		(2,186)	[1]	(2,528)	[2]	(4,359)	[3]	(6,481)	[4]
Earnings available to common shareholders		8,815	[1]	5,067	[2]	17,214	[3]	12,637	[4]
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		34,778	[1]	38,957	[2]	107,586	[3]	116,910	[4]
Property and casualty insurance premiums			[1]		[2]		[3]		[4]
Net investment and interest income		24,248	[1]	21,887	[2]	66,435	[3]	62,531	[4]
Other revenue		1,409	[1]	1,535	[2]	3,889	[3]	4,024	[4]
Total revenues		60,435	[1]	62,379	[2]	177,910	[3]	183,465	[4]
Costs and expenses:
Operating expenses		5,216	[1]	5,521	[2]	16,275	[3]	16,669	[4]
Commission expenses			[1]		[2]		[3]		[4]
Cost of sales			[1]		[2]		[3]		[4]
Benefits and losses		41,136	[1]	40,524	[2]	126,239	[3]	128,043	[4]
Amortization of deferred policy acquisition costs		6,654	[1]	5,952	[2]	18,584	[3]	18,217	[4]
Lease expense			[1]		[2]		[3]		[4]
Depreciation, net of (gains) losses on disposals			[1]		[2]		[3]		[4]
Net gains on disposal of real estate			[1]		[2]		[3]		[4]
Total costs and expenses		53,006	[1]	51,997	[2]	161,098	[3]	162,929	[4]
Earnings (loss) from operations before equity in earnings of subsidiaries		7,429	[1]	10,382	[2]	16,812	[3]	20,536	[4]
Equity in earnings of subsidiaries			[1]		[2]		[3]		[4]
Earnings from operations		7,429	[1]	10,382	[2]	16,812	[3]	20,536	[4]
Other components of net periodic benefit recovery costs			[1]		[2]		[3]		[4]
Interest expense			[1]		[2]		[3]		[4]
Pretax earnings		7,429	[1]	10,382	[2]	16,812	[3]	20,536	[4]
Income tax (expense) benefit		(1,580)	[1]	(3,626)	[2]	(3,720)	[3]	(7,175)	[4]
Earnings available to common shareholders		5,849	[1]	6,756	[2]	13,092	[3]	13,361	[4]
Consolidation, Eliminations [Member]
Revenues:
Self-moving equipment rentals	[5]	(1,407)		(1,217)		(3,669)		(3,213)
Self-storage revenues
Self-moving and self-storage products and service sales
Property management fees
Life insurance premiums
Property and casualty insurance premiums		(460)		(661)		(1,716)		(1,133)
Net investment and interest income	[6]	(419)		(373)		(1,258)		(1,157)
Other revenue	[6]	(132)		(132)		(396)		(395)
Total revenues		(2,418)		(2,383)		(7,039)	[6]	(5,898)
Costs and expenses:
Operating expenses	[5],[6]	(1,995)		(2,004)		(5,768)		(4,716)
Commission expenses
Cost of sales
Benefits and losses
Amortization of deferred policy acquisition costs
Lease expense	[6]	(136)		(83)		(408)		(183)
Depreciation, net of (gains) losses on disposals
Net gains on disposal of real estate
Total costs and expenses		(2,131)		(2,087)		(6,176)		(4,899)
Earnings (loss) from operations before equity in earnings of subsidiaries		(287)		(296)		(863)		(999)
Equity in earnings of subsidiaries	[7]	(14,664)		(11,823)		(30,306)		(25,998)
Earnings from operations		(14,951)		(12,119)		(31,169)		(26,997)
Other components of net periodic benefit recovery costs
Interest expense	[6]	287		296		863		999
Pretax earnings		(14,664)		(11,823)		(30,306)		(25,998)
Income tax (expense) benefit
Earnings available to common shareholders		$ (14,664)		$ (11,823)		$ (30,306)		$ (25,998)

[1] Balances for the quarter ended September 30, 2018

[2] Balances for the quarter ended September 30, 2017

[3] Balances for the nine months ended September 30, 2018

[4] Balances for the nine months ended September 30, 2017

[5] Eliminate intercompany premiums

[6] Eliminate intercompany lease / interest income

[7] Eliminate equity in earnings of subsidiaries