Consolidating financial information by industry segment (Cash Flow Statements) (Details) - USD ($) $ in Thousands		3 Months Ended				6 Months Ended
		Sep. 30, 2017		Sep. 30, 2016		Sep. 30, 2017		Sep. 30, 2016
Cash flow from operating activities:
Net earnings		$ 124,639		$ 176,475		$ 250,846		$ 323,648
Earnings from consolidated entities
Adjustments to reconcile net earnings to cash provided by operations:
Depreciation						269,505		233,543
Amortization of deferred policy acquisition costs		5,944		5,989		12,265		13,931
Amortization of debt issuance costs						1,946		1,765
Interest credited to policyholders						15,119		11,028
Change in allowance for losses on trade receivables						(2)		34
Change in allowance for inventory reserves						2,953		800
Net gain on sale of real and personal property		(5,104)		(9,618)		(9,845)		(28,258)
Net (gain) loss on sale of investments						(3,059)		(4,645)
Deferred income tax						63,065		114,724
Net change in other operating assets and liabilities:
Reinsurance recoverables and trade receivables						(15,895)		(8,102)
Inventories						(21,036)		(2,674)
Prepaid expenses						41,486		46,248
Capitalization of deferred policy acquisition costs						(15,154)		(14,360)
Other assets						16,615		(8,695)
Related party assets						8,958		5,195
Accounts payable and accrued expenses						69,550		45,162
Policy benefits and losses, claims and loss expenses payable						12,057		16,922
Other policyholders' funds and liabilities						10,305		1,563
Deferred income						3,660		5,034
Related party liabilities						(3,662)		232
Net cash provided by operating activities						709,677		753,095
Cash flow from investing activities:
Property, plant and equipment						(754,052)		(761,277)
Short term investments						(34,765)		(409,925)
Fixed maturities investments						(219,620)		(168,817)
Equity securities						(662)		(489)
Preferred stock						(1,000)
Real estate						(118)		(15,788)
Mortgage loans						(50,817)		(136,682)
Proceeds from sale of:
Property, plant and equipment						259,450		310,409
Short term investments						38,927		386,508
Fixed maturities investments						70,792		120,525
Preferred stock						988		2,651
Equity securities
Real estate						2,664		831
Mortgage loans						9,584		105,731
Net cash used by investing activities						(678,629)		(566,323)
Cash flow from financing activities:
Borrowings from credit facilities						285,532		331,787
Principal repayments on credit facilities						(214,354)		(158,479)
Debt issuance costs						(3,413)		(2,085)
Capital lease payments						(150,302)		(83,414)
Employee Stock Ownership Plan						(3,960)		(4,653)
Securitization deposits						(186)		245
Common stock dividends paid						(19,587)		(19,586)
Investment contract deposits						232,752		130,166
Investment contract withdrawals						(97,262)		(49,555)
Net cash provided by (used in) financing activities						29,220		144,426
Effects of exchange rate on cash						10,277		(10,517)
Increase (decrease) in cash and cash equivalents						70,545		320,681
Cash and cash equivalents at the beginning of period						697,806		600,646
Cash and cash equivalents at the end of the period		768,351		921,327		768,351		921,327
Operating Segments [Member] | Moving and Storage Consolidations [Member]
Cash flow from operating activities:
Net earnings		124,639		176,475		250,846		323,648
Earnings from consolidated entities						(14,175)		(16,879)
Adjustments to reconcile net earnings to cash provided by operations:
Depreciation						269,505		233,543
Amortization of deferred policy acquisition costs
Amortization of debt issuance costs						1,946		1,765
Interest credited to policyholders
Change in allowance for losses on trade receivables						(16)		92
Change in allowance for inventory reserves						2,953		800
Net gain on sale of real and personal property						(9,845)		(28,258)
Net (gain) loss on sale of investments
Deferred income tax						65,587		114,112
Net change in other operating assets and liabilities:
Reinsurance recoverables and trade receivables						(21,782)		(6,265)
Inventories						(21,036)		(2,674)
Prepaid expenses						41,486		46,248
Capitalization of deferred policy acquisition costs
Other assets						15,197		(10,925)
Related party assets						6,056		5,718
Accounts payable and accrued expenses						59,671		41,958
Policy benefits and losses, claims and loss expenses payable						16,081		13,165
Other policyholders' funds and liabilities
Deferred income						3,660		5,034
Related party liabilities						(3,945)		(170)
Net cash provided by operating activities						662,189		720,912
Cash flow from investing activities:
Property, plant and equipment						(754,052)		(761,277)
Short term investments
Fixed maturities investments
Equity securities
Preferred stock
Real estate								(3,510)
Mortgage loans								(1,982)
Proceeds from sale of:
Property, plant and equipment						259,450		310,409
Short term investments
Fixed maturities investments
Preferred stock
Equity securities
Real estate						2,664
Mortgage loans								4,345
Net cash used by investing activities						(491,938)		(452,015)
Cash flow from financing activities:
Borrowings from credit facilities						285,532		304,787
Principal repayments on credit facilities						(214,354)		(131,479)
Debt issuance costs						(3,413)		(2,085)
Capital lease payments						(150,302)		(83,414)
Employee Stock Ownership Plan						(3,960)		(4,653)
Securitization deposits						(186)		245
Common stock dividends paid						(19,587)		(19,586)
Investment contract deposits
Investment contract withdrawals
Net cash provided by (used in) financing activities						(106,270)		63,815
Effects of exchange rate on cash						10,277		(10,517)
Increase (decrease) in cash and cash equivalents						74,258		322,195
Cash and cash equivalents at the beginning of period						671,665		585,666
Cash and cash equivalents at the end of the period		745,923		907,861		745,923		907,861
Operating Segments [Member] | Property and Casualty Insurance [Member]
Cash flow from operating activities:
Net earnings		3,996	[1]	4,688	[2]	7,570	[3]	9,565	[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							[3]		[4]
Interest credited to policyholders							[3]		[4]
Change in allowance for losses on trade receivables							[3]		[4]
Change in allowance for inventory reserves							[3]		[4]
Net gain on sale of real and personal property							[3]		[4]
Net (gain) loss on sale of investments						(748)	[3]	(2,709)	[4]
Deferred income tax						(1,730)	[3]	24	[4]
Net change in other operating assets and liabilities:
Reinsurance recoverables and trade receivables						6,281	[3]	429	[4]
Inventories							[3]		[4]
Prepaid expenses							[3]		[4]
Capitalization of deferred policy acquisition costs							[3]		[4]
Other assets						1,563	[3]	2,150	[4]
Related party assets						2,902	[3]	(523)	[4]
Accounts payable and accrued expenses						3,282	[3]	1,766	[4]
Policy benefits and losses, claims and loss expenses payable						(5,604)	[3]	(2,888)	[4]
Other policyholders' funds and liabilities						5,685	[3]	566	[4]
Deferred income							[3]		[4]
Related party liabilities						292	[3]	456	[4]
Net cash provided by operating activities						19,493	[3]	8,836	[4]
Cash flow from investing activities:
Property, plant and equipment							[3]		[4]
Short term investments						(27,059)	[3]	(36,646)	[4]
Fixed maturities investments						(29,381)	[3]	(13,469)	[4]
Equity securities							[3]		[4]
Preferred stock	[3]					(1,000)
Real estate							[3]	(4,580)	[4]
Mortgage loans						(7,609)	[3]	(3,063)	[4]
Proceeds from sale of:
Property, plant and equipment							[3]		[4]
Short term investments						28,879	[3]	17,771	[4]
Fixed maturities investments						12,033	[3]	16,623	[4]
Preferred stock						988	[3]	2,651	[4]
Equity securities	[4]
Real estate	[3]
Mortgage loans						1,722	[3]	9,603	[4]
Net cash used by investing activities						(21,427)	[3]	(11,110)	[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							[3]		[4]
Securitization deposits							[3]		[4]
Common stock dividends paid							[3]		[4]
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						(1,934)	[3]	(2,274)	[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		10,791	[8]	11,775	[4]	10,791	[8]	11,775	[4]
Operating Segments [Member] | Life Insurance [Member]
Cash flow from operating activities:
Net earnings		4,369	[1]	4,617	[2]	6,605	[3]	7,314	[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		5,944	[1]	5,989	[2]	12,265	[5]	13,931	[6]
Amortization of debt issuance costs							[3]		[4]
Interest credited to policyholders						15,119	[3]	11,028	[4]
Change in allowance for losses on trade receivables						14	[3]	(58)	[4]
Change in allowance for inventory reserves							[3]		[4]
Net gain on sale of real and personal property							[3]		[4]
Net (gain) loss on sale of investments						(2,311)	[3]	(1,936)	[4]
Deferred income tax						(792)	[3]	588	[4]
Net change in other operating assets and liabilities:
Reinsurance recoverables and trade receivables						(394)	[3]	(2,266)	[4]
Inventories							[3]		[4]
Prepaid expenses							[3]		[4]
Capitalization of deferred policy acquisition costs						(15,154)	[3]	(14,360)	[4]
Other assets						(145)	[3]	80	[4]
Related party assets							[3]		[4]
Accounts payable and accrued expenses						6,597	[3]	1,438	[4]
Policy benefits and losses, claims and loss expenses payable						1,580	[3]	6,645	[4]
Other policyholders' funds and liabilities						4,620	[3]	997	[4]
Deferred income							[3]		[4]
Related party liabilities						(9)	[3]	(54)	[4]
Net cash provided by operating activities						27,995	[3]	23,347	[4]
Cash flow from investing activities:
Property, plant and equipment							[3]		[4]
Short term investments						(7,706)	[3]	(373,279)	[4]
Fixed maturities investments						(190,239)	[3]	(155,348)	[4]
Equity securities						(662)	[3]	(489)	[4]
Preferred stock	[3]
Real estate						(118)	[3]	(7,698)	[4]
Mortgage loans						(43,208)	[3]	(131,637)	[4]
Proceeds from sale of:
Property, plant and equipment							[3]		[4]
Short term investments						10,048	[3]	368,737	[4]
Fixed maturities investments						58,759	[3]	103,902	[4]
Preferred stock							[3]		[4]
Equity securities	[4]							831
Real estate	[3]
Mortgage loans						7,862	[3]	91,783	[4]
Net cash used by investing activities						(165,264)	[3]	(103,198)	[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							[3]		[4]
Securitization deposits							[3]		[4]
Common stock dividends paid							[3]		[4]
Investment contract deposits						232,752	[3]	130,166	[4]
Investment contract withdrawals						(97,262)	[3]	(49,555)	[4]
Net cash provided by (used in) financing activities						135,490	[3]	80,611	[4]
Effects of exchange rate on cash							[3]		[4]
Increase (decrease) in cash and cash equivalents						(1,779)	[3]	760	[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		11,637	[8]	1,691	[4]	11,637	[8]	1,691	[4]
Consolidation, Eliminations [Member]
Cash flow from operating activities:
Net earnings		(8,365)		(9,305)		(14,175)		(16,879)
Earnings from consolidated entities						14,175		16,879
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 real and personal property
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
Accounts payable and accrued expenses
Policy benefits and losses, claims and loss expenses payable
Other policyholders' funds and liabilities
Deferred income
Related party liabilities
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
Proceeds from sale of:
Property, plant and equipment
Short term investments
Fixed maturities investments
Preferred stock
Equity securities
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 June 30, 2017

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

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

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

[5] Balances for the six months ended June 30, 2017

[6] Balances for the six months ended June 30, 2016

[7] Balances as of December 31, 2016

[8] Balances as of June 30, 2017