Consolidating financial information by industry segment (Cash Flow Statements) (Details) - USD ($) $ in Thousands	3 Months Ended				9 Months Ended
	Dec. 31, 2017		Dec. 31, 2016		Dec. 31, 2017		Dec. 31, 2016
Cash flow from operating activities:
Net earnings	$ 528,894		$ 65,228		$ 779,740		$ 388,876
Earnings from consolidated entities
Adjustments to reconcile net earnings to cash provided by operations:
Depreciation					410,800		354,183
Amortization of deferred policy acquisition costs	5,952		5,200		18,217		19,131
Amortization of debt issuance costs					2,910		3,125
Interest credited to policyholders					23,250		18,190
Change in allowance for losses on trade receivables					(25)		(28)
Change in allowance for inventory reserves					4,334		1,897
Net gain on sale of personal property	(4,235)		(2,099)		(14,260)		(30,398)
Net gains on disposal of real estate	(192,404)		(2,418)		(192,223)		(2,377)
Net (gain) loss on sale of investments					(4,250)		(3,948)
Deferred income tax					(179,047)		112,448
Net change in other operating assets and liabilities:
Reinsurance recoverables and trade receivables					(27,659)		(23,919)
Inventories					(17,410)		(1,901)
Prepaid expenses					(22,220)		79,578
Capitalization of deferred policy acquisition costs					(21,501)		(21,040)
Other assets					6,279		(663)
Related party assets					47,804		(5,469)
Accounts payable and accrued expenses					26,764		30,773
Policy benefits and losses, claims and loss expenses payable					2,767		12,843
Other policyholders' funds and liabilities					590		(382)
Deferred income					(1,297)		1,105
Related party liabilities					(4,542)		(711)
Net cash provided by operating activities					839,021		931,313
Cash flow from investing activities:
Escrow Deposits					19,707		(768)
Purchases of:
Property, plant and equipment					(970,472)		(981,316)
Short term investments					(48,743)		(566,371)
Fixed maturities investments					(274,283)		(261,851)
Equity securities					(662)		(489)
Preferred stock					(1,000)
Real estate					(1,783)		(15,863)
Mortgage loans					(80,707)		(159,309)
Proceeds from sale of:
Property, plant and equipment					591,040		412,892
Short term investments					54,319		566,955
Fixed maturities investments					102,404		147,233
Preferred stock					3,188		3,351
Real estate					5,348		1,681
Mortgage loans					23,726		109,260
Net cash used by investing activities					(577,918)		(744,595)
Cash flow from financing activities:
Borrowings from credit facilities					426,262		534,008
Principal repayments on credit facilities					(303,212)		(244,545)
Debt issuance costs					(4,581)		(4,529)
Capital lease payments					(219,623)		(141,750)
Employee stock ownership plan					(6,764)		(7,541)
Securitization deposits					(2,181)		371
Common stock dividends paid					(19,587)		(39,171)
Investment contract deposits					347,695		180,554
Investment contract withdrawals					(163,499)		(64,459)
Net cash provided by (used in) financing activities					54,510		212,938
Effects of exchange rate on cash					9,468		(16,117)
Increase (decrease) in cash and cash equivalents					325,081		383,539
Cash and cash equivalents at the beginning of period					697,806		600,646
Cash and cash equivalents at the end of the period	1,022,887		984,185		1,022,887		984,185
Operating Segments [Member] | Moving and Storage Consolidations [Member]
Cash flow from operating activities:
Net earnings	528,894		65,228		779,740		388,876
Earnings from consolidated entities					(25,998)		(25,925)
Adjustments to reconcile net earnings to cash provided by operations:
Depreciation					410,800		354,183
Amortization of deferred policy acquisition costs
Amortization of debt issuance costs					2,910		3,125
Interest credited to policyholders
Change in allowance for losses on trade receivables					(22)		22
Change in allowance for inventory reserves					4,334		1,897
Net gain on sale of personal property					(14,260)		(30,398)
Net gains on disposal of real estate	(192,404)		(2,418)		(192,223)		(2,377)
Net (gain) loss on sale of investments
Deferred income tax					(176,566)		114,017
Net change in other operating assets and liabilities:
Reinsurance recoverables and trade receivables					(32,898)		(24,147)
Inventories					(17,410)		(1,901)
Prepaid expenses					(22,220)		79,578
Capitalization of deferred policy acquisition costs
Other assets					4,649		(3,185)
Related party assets					43,822		(5,906)
Accounts payable and accrued expenses					15,455		22,313
Policy benefits and losses, claims and loss expenses payable					8,427		11,805
Other policyholders' funds and liabilities
Deferred income					(1,297)		1,105
Related party liabilities					(4,412)		(1,018)
Net cash provided by operating activities					782,831		882,064
Cash flow from investing activities:
Escrow Deposits					19,707		(768)
Purchases of:
Property, plant and equipment					(970,472)		(981,316)
Short term investments
Fixed maturities investments
Equity securities
Preferred stock
Real estate					(1,637)		(3,510)
Mortgage loans							(9,738)
Proceeds from sale of:
Property, plant and equipment					591,040		412,892
Short term investments
Fixed maturities investments
Preferred stock
Real estate					5,348
Mortgage loans							4,986
Net cash used by investing activities					(356,014)		(577,454)
Cash flow from financing activities:
Borrowings from credit facilities					426,262		507,008
Principal repayments on credit facilities					(303,212)		(217,545)
Debt issuance costs					(4,581)		(4,529)
Capital lease payments					(219,623)		(141,750)
Employee stock ownership plan					6,764		(7,541)
Securitization deposits					(2,181)		371
Common stock dividends paid					(19,587)		39,171
Investment contract deposits
Investment contract withdrawals
Net cash provided by (used in) financing activities					(129,686)		96,843
Effects of exchange rate on cash					9,468		(16,117)
Increase (decrease) in cash and cash equivalents					306,599		385,336
Cash and cash equivalents at the beginning of period					671,665		585,666
Cash and cash equivalents at the end of the period	978,264		971,002		978,264		971,002
Operating Segments [Member] | Property and Casualty Insurance [Member]
Cash flow from operating activities:
Net earnings	5,067	[1]	4,731	[2]	12,637	[3]	14,296	[4]
Earnings from consolidated entities						[3]		[4]
Adjustments to reconcile net earnings to cash provided by operations:
Depreciation						[3]		[4]
Amortization of deferred policy acquisition costs		[1]		[2]		[5]		[6]
Amortization of debt issuance costs
Interest credited to policyholders
Change in allowance for losses on trade receivables						[3]		[4]
Change in allowance for inventory reserves						[3]		[4]
Net gain on sale of personal property						[3]		[4]
Net gains on disposal of real estate
Net (gain) loss on sale of investments					(881)	[3]	(2,717)	[4]
Deferred income tax					(1,315)	[3]	(549)	[4]
Net change in other operating assets and liabilities:
Reinsurance recoverables and trade receivables					6,908	[3]	2,388	[4]
Inventories						[3]		[4]
Prepaid expenses						[3]		[4]
Capitalization of deferred policy acquisition costs						[3]		[4]
Other assets					1,796	[3]	2,439	[4]
Related party assets					3,982	[3]	437	[4]
Accounts payable and accrued expenses					1,229	[3]	2,363	[4]
Policy benefits and losses, claims and loss expenses payable					(6,896)	[3]	(5,650)	[4]
Other policyholders' funds and liabilities					1,099	[3]	1,024	[4]
Deferred income						[3]		[4]
Related party liabilities					(205)	[3]	371	[4]
Net cash provided by operating activities					18,354	[3]	14,402	[4]
Cash flow from investing activities:
Escrow Deposits
Purchases of:
Property, plant and equipment						[3]		[4]
Short term investments					(39,701)	[3]	(67,094)	[4]
Fixed maturities investments					(34,284)	[3]	(22,138)	[4]
Equity securities								[4]
Preferred stock					(1,000)
Real estate					(16)	[3]	(4,648)	[4]
Mortgage loans					(11,609)	[3]	(16,686)	[4]
Proceeds from sale of:
Property, plant and equipment						[3]		[4]
Short term investments					43,570	[3]	59,583	[4]
Fixed maturities investments					17,821	[3]	20,697	[4]
Preferred stock					3,188		3,351
Real estate
Mortgage loans					3,248		9,742	[4]
Net cash used by investing activities					(18,783)		(17,193)	[4]
Cash flow from financing activities:
Borrowings from credit facilities						[3]		[4]
Principal repayments on credit facilities						[3]		[4]
Debt issuance costs						[3]		[4]
Capital lease payments						[3]		[4]
Employee stock ownership plan
Securitization deposits						[3]
Common stock dividends paid						[3]
Investment contract deposits						[3]		[4]
Investment contract withdrawals						[3]		[4]
Net cash provided by (used in) financing activities						[3]		[4]
Effects of exchange rate on cash						[3]		[4]
Increase (decrease) in cash and cash equivalents					(429)	[3]	(2,791)	[4]
Cash and cash equivalents at the beginning of period					12,725	[7]	14,049	[4]
Cash and cash equivalents at the end of the period	12,296	[8]	11,258	[4]	12,296	[8]	11,258	[4]
Operating Segments [Member] | Life Insurance [Member]
Cash flow from operating activities:
Net earnings	6,756	[1]	4,315	[2]	13,361	[3]	11,629	[4]
Earnings from consolidated entities						[3]		[4]
Adjustments to reconcile net earnings to cash provided by operations:
Depreciation						[3]		[4]
Amortization of deferred policy acquisition costs	5,952	[1]	5,200	[2]	18,217	[5]	19,131	[6]
Amortization of debt issuance costs
Interest credited to policyholders					23,250		18,190
Change in allowance for losses on trade receivables					(3)	[3]	(50)	[4]
Change in allowance for inventory reserves						[3]		[4]
Net gain on sale of personal property						[3]		[4]
Net gains on disposal of real estate
Net (gain) loss on sale of investments					(3,369)	[3]	(1,231)	[4]
Deferred income tax					(1,166)	[3]	(1,020)	[4]
Net change in other operating assets and liabilities:
Reinsurance recoverables and trade receivables					(1,669)	[3]	(2,160)	[4]
Inventories						[3]		[4]
Prepaid expenses						[3]		[4]
Capitalization of deferred policy acquisition costs					(21,501)	[3]	(21,040)	[4]
Other assets					(166)	[3]	83	[4]
Related party assets						[3]		[4]
Accounts payable and accrued expenses					10,080	[3]	6,097	[4]
Policy benefits and losses, claims and loss expenses payable					1,236	[3]	6,688	[4]
Other policyholders' funds and liabilities					(509)	[3]	(1,406)	[4]
Deferred income						[3]		[4]
Related party liabilities					75	[3]	(64)	[4]
Net cash provided by operating activities					37,836	[3]	34,847	[4]
Cash flow from investing activities:
Escrow Deposits
Purchases of:
Property, plant and equipment						[3]		[4]
Short term investments					(9,042)	[3]	(499,277)	[4]
Fixed maturities investments					(239,999)	[3]	(239,713)	[4]
Equity securities					(662)		(489)	[4]
Preferred stock
Real estate					(130)	[3]	(7,705)	[4]
Mortgage loans					(69,098)	[3]	(132,885)	[4]
Proceeds from sale of:
Property, plant and equipment						[3]		[4]
Short term investments					10,749	[3]	507,372	[4]
Fixed maturities investments					84,583	[3]	126,536	[4]
Preferred stock
Real estate							1,681
Mortgage loans					20,478		94,532	[4]
Net cash used by investing activities					(203,121)		(149,948)	[4]
Cash flow from financing activities:
Borrowings from credit facilities						[3]	27,000	[4]
Principal repayments on credit facilities						[3]	(27,000)	[4]
Debt issuance costs						[3]		[4]
Capital lease payments						[3]		[4]
Employee stock ownership plan
Securitization deposits						[3]
Common stock dividends paid						[3]
Investment contract deposits					347,695	[3]	180,554	[4]
Investment contract withdrawals					(163,499)	[3]	(64,459)	[4]
Net cash provided by (used in) financing activities					184,196	[3]	116,095	[4]
Effects of exchange rate on cash						[3]		[4]
Increase (decrease) in cash and cash equivalents					18,911	[3]	994	[4]
Cash and cash equivalents at the beginning of period					13,416	[7]	931	[4]
Cash and cash equivalents at the end of the period	32,327	[8]	1,925	[4]	32,327	[8]	1,925	[4]
Consolidation, Eliminations [Member]
Cash flow from operating activities:
Net earnings	(11,823)		(9,046)		(25,998)		(25,925)
Earnings from consolidated entities					25,998		25,925
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 policyholders
Change in allowance for losses on trade receivables
Change in allowance for inventory reserves
Net gain on sale of personal property
Net gains on disposal of real estate
Net (gain) loss on sale of investments
Deferred income tax
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								[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								[9]
Net cash provided by operating activities
Cash flow from investing activities:
Escrow Deposits
Purchases of:
Property, plant and equipment
Short term investments
Fixed maturities investments
Equity securities
Preferred stock
Real estate
Mortgage loans
Proceeds from sale of:
Property, plant and equipment
Short term investments
Fixed maturities investments
Preferred stock
Real estate
Mortgage loans
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 (used in) 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 quarter ended September 30, 2017

[2] Balances for the quarter ended September 30, 2016

[3] Balance for the period ended September 30, 2017

[4] Balance for the period ended September 30, 2016

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

[6] Balances for the nine months ended September 30, 2016

[7] Balances as of December 31, 2016

[8] Balances as of September 30, 2017

[9] Elimination of intercompany investments