Consolidating financial information by industry segment (Cash Flow Statements) (Details) - USD ($) $ in Thousands	12 Months Ended
	Mar. 31, 2017		Mar. 31, 2016		Mar. 31, 2015
Cash flow from operating activities:
Net earnings	$ 398,424		$ 489,001		$ 356,741
Earnings from consolidated subsidiaries
Adjustments to reconcile net earnings to cash provided by operations:
Depreciation	481,520		389,393		352,796
Amortization of deferred policy acquisition costs	26,218		23,272		19,661
Amortization of debt issuance costs	4,062		3,419		3,786
Interest credited to policy holders	25,020		20,465		18,110
Change in allowance for losses on trade receivables	(46)		(205)		(168)
Change in allowance for inventory reserves	1,330		(1,343)		(872)
Net gain on sale of real and personal property	(36,085)		(98,703)		(74,631)
Net gain (loss) on sale of investments	(5,284)		(4,491)		(3,925)
Deferred income taxes	173,112		138,075		76,500
Net change in other operating assets and liabilities:
Reinsurance recoverables and trade receivables	(2,890)		14,765		9,632
Inventories	(4,072)		(9,009)		(1,579)
Prepaid expenses	9,386		(10,338)		(65,720)
Capitalization of deferred policy acquisition costs	(27,111)		(32,590)		(27,084)
Other assets	(40,546)		11,903		(51)
Related party assets	343		56,644		27,706
Accounts payable and accrued expenses	(5,056)		37,312		98,877
Policy benefits and losses, claims and loss expenses payable	15,378		9,626		(17,621)
Other policyholders' funds and liabilities	1,499		(349)		988
Deferred income	5,921		4,757		(13,181)
Related party liabilities	(1,062)		(616)		(866)
Net cash provided by operating activities	1,020,061		1,040,988		759,099
Cash flow from investing activities:
Property, plant and equipment	(1,419,505)		(1,509,154)		(1,041,931)
Short term investments	(635,847)		(515,899)		(290,379)
Fixed maturities investments	(355,101)		(398,987)		(214,371)
Equity securities	(489)		(1,315)		(3,759)
Preferred stock			(1,005)		(2,006)
Real estate	(32,807)		(15,459)		(38,275)
Mortgage loans	(154,310)		(87,204)		(19,807)
Proceeds from sale and paydowns of:
Property, plant and equipment	487,475		539,256		411,629
Short term investments	655,726		528,180		287,883
Fixed maturities investments	190,578		154,536		107,867
Equity securities			2,044		3,082
Preferred stock	4,181		1,126		2,427
Real estate	8,753		21,589		28,485
Mortgage loans	106,832		26,968		13,894
Net cash used by investing activities	(1,144,514)		(1,255,324)		(755,261)
Cash flow from financing activities:
Borrowings from credit facilities	742,625		837,972		657,535
Principal repayments on credit facilities	(367,844)		(428,403)		(593,722)
Debt issuance costs	(5,055)		(10,184)		(12,327)
Capital lease payments	(212,545)		(168,661)		(121,202)
Employee stock ownership plan	(11,106)		(9,302)		(7,939)
Securitization deposits	446		544
Common stock dividends paid	(58,757)		(78,374)		(19,594)
Investment contract deposits	285,148		358,237		105,019
Investment contract withdrawals	(149,159)		(112,957)		(54,108)
Net cash provided by financing activities	223,753		388,872		(46,338)
Effects of exchange rate on cash	(2,140)		(15,740)		(10,762)
Increase (decrease) in cash and cash equivalents	97,160		158,796		(53,262)
Cash and cash equivalents at the beginning of period	600,646		441,850		495,112
Cash and cash equivalents at the end of the period	697,806		600,646		441,850
Operating Segments [Member] | Moving and Storage Consolidations [Member]
Cash flow from operating activities:
Net earnings	398,424		489,001		356,741
Earnings from consolidated subsidiaries	(35,797)		(35,522)		(34,783)
Adjustments to reconcile net earnings to cash provided by operations:
Depreciation	481,520		389,393		352,796
Amortization of deferred policy acquisition costs
Amortization of debt issuance costs	4,062		3,419		3,786
Interest credited to policy holders
Change in allowance for losses on trade receivables	31		7		(179)
Change in allowance for inventory reserves	1,330		(1,343)		(872)
Net gain on sale of real and personal property	(36,085)		(98,703)		(74,631)
Net gain (loss) on sale of investments
Deferred income taxes	173,059		124,838		66,628
Net change in other operating assets and liabilities:
Reinsurance recoverables and trade receivables	(6,806)		(2,169)		(3,213)
Inventories	(4,072)		(9,009)		(1,579)
Prepaid expenses	9,386		(10,338)		(65,720)
Capitalization of deferred policy acquisition costs
Other assets	(41,885)		12,812		651
Related party assets	(872)		55,962		27,753
Accounts payable and accrued expenses	(14,793)		26,018		91,409
Policy benefits and losses, claims and loss expenses payable	13,283		23,215		(4,327)
Other policyholders' funds and liabilities
Deferred income	5,921		4,757		(13,181)
Related party liabilities	(1,170)		17,296		(1,016)
Net cash provided by operating activities	945,536		989,634		700,263
Cash flow from investing activities:
Property, plant and equipment	(1,419,505)		(1,509,154)		(1,041,931)
Short term investments
Fixed maturities investments
Equity securities
Preferred stock
Real estate	(19,406)		(15,384)		(22,876)
Mortgage loans
Proceeds from sale and paydowns of:
Property, plant and equipment	487,475		539,256		411,629
Short term investments
Fixed maturities investments
Equity securities
Preferred stock
Real estate			21,589		28,089
Mortgage loans	6,275
Net cash used by investing activities	(945,161)		(963,693)		(625,089)
Cash flow from financing activities:
Borrowings from credit facilities	715,625		790,972		657,535
Principal repayments on credit facilities	(340,844)		(381,403)		(593,722)
Debt issuance costs	(5,055)		(10,184)		(12,327)
Capital lease payments	(212,545)		(168,661)		(121,202)
Employee stock ownership plan	(11,106)		(9,302)		(7,939)
Securitization deposits	446		544
Common stock dividends paid	(58,757)		(78,374)		(19,594)
Investment contract deposits
Investment contract withdrawals
Net cash provided by financing activities	87,764		143,592		(97,249)
Effects of exchange rate on cash	(2,140)		(15,740)		(10,762)
Increase (decrease) in cash and cash equivalents	85,999		153,793		(32,837)
Cash and cash equivalents at the beginning of period	585,666		431,873		464,710
Cash and cash equivalents at the end of the period	671,665		585,666		431,873
Operating Segments [Member] | Property and Casualty Insurance [Member]
Cash flow from operating activities:
Net earnings	17,815	[1]	16,168	[2]	15,417	[3]
Earnings from consolidated subsidiaries		[4]		[5]		[6]
Adjustments to reconcile net earnings to cash provided by operations:
Depreciation		[4]		[5]		[6]
Amortization of deferred policy acquisition costs		[1]		[2]		[3]
Amortization of debt issuance costs
Interest credited to policy holders		[4]		[5]		[6]
Change in allowance for losses on trade receivables		[4]		[5]		[6]
Change in allowance for inventory reserves		[4]		[5]		[6]
Net gain on sale of real and personal property		[4]		[5]		[6]
Net gain (loss) on sale of investments	(2,636)	[4]	(1,317)	[5]	(841)	[6]
Deferred income taxes	2,340	[4]	9,311	[5]	8,030	[6]
Net change in other operating assets and liabilities:
Reinsurance recoverables and trade receivables	4,221	[4]	13,528	[5]	16,830	[6]
Inventories		[4]		[5]		[6]
Prepaid expenses		[4]		[5]		[6]
Capitalization of deferred policy acquisition costs		[4]		[5]		[6]
Other assets	1,341	[4]	(1,050)	[5]	102	[6]
Related party assets	1,215	[4]	682	[5]	(258)	[6]
Accounts payable and accrued expenses	392	[4]	1,533	[5]	22	[6]
Policy benefits and losses, claims and loss expenses payable	(7,838)	[4]	(18,925)	[5]	(23,472)	[6]
Other policyholders' funds and liabilities	1,167	[4]	(1,056)	[5]	317	[6]
Deferred income		[4]		[5]		[6]
Related party liabilities	226	[4]	115	[5]	428	[6]
Net cash provided by operating activities	18,243	[4]	18,989	[5]	16,575	[6]
Cash flow from investing activities:
Property, plant and equipment		[4]		[5]		[6]
Short term investments	(77,693)	[4]	(44,735)	[5]	(40,583)	[6]
Fixed maturities investments	(42,628)	[4]	(45,048)	[5]	(43,062)	[6]
Equity securities		[4]		[5]	(3,333)	[6]
Preferred stock			(1,005)	[5]	(1,006)	[6]
Real estate	(4,648)	[4]	(36)	[5]	(7,857)	[6]
Mortgage loans	(21,021)	[4]	(1,800)	[5]	(4,350)	[6]
Proceeds from sale and paydowns of:
Property, plant and equipment		[4]		[5]		[6]
Short term investments	80,225	[4]	44,756	[5]	53,112	[6]
Fixed maturities investments	32,127	[4]	26,193	[5]	18,556	[6]
Equity securities			1,236	[5]	3,082	[6]
Preferred stock	4,181	[4]	1,126	[5]	400	[6]
Real estate		[4]				[6]
Mortgage loans	9,890	[4]	5,878	[5]	4,203	[6]
Net cash used by investing activities	(19,567)	[4]	(13,435)	[5]	(20,838)	[6]
Cash flow from financing activities:
Borrowings from credit facilities		[4]		[5]		[6]
Principal repayments on credit facilities		[4]		[5]		[6]
Debt issuance costs		[4]		[5]		[6]
Capital lease payments		[4]		[5]		[6]
Employee stock ownership plan		[4]		[5]		[6]
Securitization deposits		[4]
Common stock dividends paid		[4]		[5]		[6]
Investment contract deposits		[4]		[5]		[6]
Investment contract withdrawals		[4]		[5]		[6]
Net cash provided by financing activities		[4]		[5]		[6]
Effects of exchange rate on cash		[4]		[5]		[6]
Increase (decrease) in cash and cash equivalents	(1,324)	[4]	5,554	[5]	(4,263)	[6]
Cash and cash equivalents at the beginning of period	14,049	[7]	8,495	[6]	12,758	[6]
Cash and cash equivalents at the end of the period	12,725	[8]	14,049	[7]	8,495	[6]
Operating Segments [Member] | Life Insurance [Member]
Cash flow from operating activities:
Net earnings	17,982	[1]	19,354	[2]	19,366	[3]
Earnings from consolidated subsidiaries		[4]		[5]		[6]
Adjustments to reconcile net earnings to cash provided by operations:
Depreciation		[4]		[5]		[6]
Amortization of deferred policy acquisition costs	26,218	[1]	23,272	[2]	19,661	[3]
Amortization of debt issuance costs
Interest credited to policy holders	25,020	[4]	20,465	[5]	18,110	[6]
Change in allowance for losses on trade receivables	(77)	[4]	(212)	[5]	11	[6]
Change in allowance for inventory reserves		[4]		[5]		[6]
Net gain on sale of real and personal property		[4]		[5]		[6]
Net gain (loss) on sale of investments	(2,648)	[4]	(3,174)	[5]	(3,084)	[6]
Deferred income taxes	(2,287)	[4]	3,926	[5]	1,842	[6]
Net change in other operating assets and liabilities:
Reinsurance recoverables and trade receivables	(305)	[4]	3,406	[5]	(3,985)	[6]
Inventories		[4]		[5]		[6]
Prepaid expenses		[4]		[5]		[6]
Capitalization of deferred policy acquisition costs	(27,111)	[4]	(32,590)	[5]	(27,084)	[6]
Other assets	(2)	[4]	141	[5]	(804)	[6]
Related party assets		[4]	(18,075)	[5]		[6]
Accounts payable and accrued expenses	9,345	[4]	9,761	[5]	7,446	[6]
Policy benefits and losses, claims and loss expenses payable	9,933	[4]	5,336	[5]	10,178	[6]
Other policyholders' funds and liabilities	332	[4]	707	[5]	671	[6]
Deferred income		[4]		[5]		[6]
Related party liabilities	(118)	[4]	48	[5]	(67)	[6]
Net cash provided by operating activities	56,282	[4]	32,365	[5]	42,261	[6]
Cash flow from investing activities:
Property, plant and equipment		[4]		[5]		[6]
Short term investments	(558,154)	[4]	(471,164)	[5]	(249,796)	[6]
Fixed maturities investments	(312,473)	[4]	(353,939)	[5]	(171,309)	[6]
Equity securities	(489)	[4]	(1,315)	[5]	(426)	[6]
Preferred stock				[5]	(1,000)	[6]
Real estate	(8,753)	[4]	(39)	[5]	(7,542)	[6]
Mortgage loans	(133,289)	[4]	(85,404)	[5]	(15,457)	[6]
Proceeds from sale and paydowns of:
Property, plant and equipment		[4]		[5]		[6]
Short term investments	575,501	[4]	483,424	[5]	234,771	[6]
Fixed maturities investments	158,451	[4]	128,343	[5]	89,311	[6]
Equity securities			808	[5]		[6]
Preferred stock		[4]		[5]	2,027	[6]
Real estate	2,478	[4]			396	[6]
Mortgage loans	96,942	[4]	21,090	[5]	9,691	[6]
Net cash used by investing activities	(179,786)	[4]	(278,196)	[5]	(109,334)	[6]
Cash flow from financing activities:
Borrowings from credit facilities	27,000	[4]	47,000	[5]		[6]
Principal repayments on credit facilities	(27,000)	[4]	(47,000)	[5]		[6]
Debt issuance costs		[4]		[5]		[6]
Capital lease payments		[4]		[5]		[6]
Employee stock ownership plan		[4]		[5]		[6]
Securitization deposits		[4]
Common stock dividends paid		[4]		[5]		[6]
Investment contract deposits	285,148	[4]	358,237	[5]	105,019	[6]
Investment contract withdrawals	(149,159)	[4]	(112,957)	[5]	(54,108)	[6]
Net cash provided by financing activities	135,989	[4]	245,280	[5]	50,911	[6]
Effects of exchange rate on cash		[4]		[5]		[6]
Increase (decrease) in cash and cash equivalents	12,485	[4]	(551)	[5]	(16,162)	[6]
Cash and cash equivalents at the beginning of period	931	[7]	1,482	[6]	17,644	[6]
Cash and cash equivalents at the end of the period	13,416	[8]	931	[7]	1,482	[6]
Eliminations [Member]
Cash flow from operating activities:
Net earnings	(35,797)		(35,522)		(34,783)
Earnings from consolidated subsidiaries	35,797		35,522		34,783
Adjustments to reconcile net earnings to cash provided by operations:
Depreciation
Amortization of deferred policy acquisition costs
Amortization of debt issuance costs
Interest credited to policy holders
Change in allowance for losses on trade receivables
Change in allowance for inventory reserves
Net gain on sale of real and personal property
Net gain (loss) on sale of investments
Deferred income taxes
Net change in other operating assets and liabilities:
Reinsurance recoverables and trade receivables
Inventories
Prepaid expenses
Capitalization of deferred policy acquisition costs
Other assets
Related party assets			18,075	[9]	211	[9]
Accounts payable and accrued expenses
Policy benefits and losses, claims and loss expenses payable
Other policyholders' funds and liabilities
Deferred income
Related party liabilities			(18,075)	[9]	(211)	[9]
Net cash provided by operating activities
Cash flow from investing activities:
Property, plant and equipment
Short term investments
Fixed maturities investments
Equity securities
Preferred stock
Real estate
Mortgage loans						[9]
Proceeds from sale and paydowns of:
Property, plant and equipment
Short term investments
Fixed maturities investments
Equity securities
Preferred stock
Real estate
Mortgage loans						[9]
Net cash used by investing activities
Cash flow from financing activities:
Borrowings from credit facilities
Principal repayments on credit facilities
Debt issuance costs
Capital lease payments
Employee stock ownership plan
Securitization deposits
Common stock dividends paid
Investment contract deposits
Investment contract withdrawals
Net cash provided by financing activities
Effects of exchange rate on cash
Increase (decrease) in cash and cash equivalents
Cash and cash equivalents at the beginning of period
Cash and cash equivalents at the end of the period

[1] Balances for the year ended December 31, 2016

[2] Balances for the year ended December 31, 2015

[3] Balances for the year ended December 31, 2014

[4] Balance for the period ended December 31, 2016

[5] Balance for the period ended December 31, 2015

[6] Balance for the period ended December 31, 2014

[7] Balances as of December 31, 2015

[8] Balances as of December 31, 2016

[9] Eliminate intercompany investments