Consolidating financial information by industry segment (Cash Flow Statements) (Details) - USD ($) $ in Thousands		3 Months Ended				9 Months Ended
		Dec. 31, 2016		Dec. 31, 2015		Dec. 31, 2016		Dec. 31, 2015
Cash flow from operating activities:
Net earnings		$ 65,228		$ 81,769		$ 388,876		$ 436,433
Earnings from consolidated entities
Adjustments to reconcile net earnings to cash provided by operations:
Depreciation						354,183		287,562
Amortization of deferred policy acquisition costs		5,200		5,138		19,131		15,559
Amortization of debt issuance costs						3,125		2,319
Interest credited to policyholders						18,190		13,844
Change in allowance for losses on trade receivables						(28)		(182)
Change in allowance for inventory reserves						1,897		(1,939)
Net gain on sale of real and personal property		(4,517)		(8,984)		(32,775)		(87,789)
Net (gain) loss on sale of investments						(3,948)		(3,779)
Deferred income tax						112,448		151,399
Net change in other operating assets and liabilities:
Reinsurance recoverables and trade receivables						(23,919)		8,568
Inventories						(1,901)		(3,887)
Prepaid expenses						79,578		(57,015)
Capitalization of deferred policy acquisition costs						(21,040)		(24,803)
Other assets						(1,431)		18,361
Related party assets						(5,469)		49,803
Accounts payable and accrued expenses						30,773		37,323
Policy benefits and losses, claims and loss expenses payable						12,843		12,976
Other policyholders' funds and liabilities						(382)		(560)
Deferred income						1,105		1,005
Related party liabilities						(711)		(878)
Net cash provided by operating activities						930,545		854,320
Cash flow from investing activities:
Property, plant and equipment						(981,316)		(1,051,830)
Short term investments						(566,371)		(391,683)
Fixed maturities investments						(261,851)		(318,664)
Equity securities						(489)		(1,315)
Preferred stock								(5)
Real estate						(15,863)		(23)
Mortgage loans						(159,309)		(99,549)
Proceeds from sale of:
Property, plant and equipment						412,892		463,602
Short term investments						566,955		400,844
Fixed maturities investments						147,233		135,727
Equity securities								808
Preferred stock						3,351
Real estate						1,681
Mortgage loans						109,260		34,141
Net cash used by investing activities						(743,827)		(827,947)
Cash flow from financing activities:
Borrowings from credit facilities						534,008		508,276
Principal repayments on credit facilities						(244,545)		(280,304)
Debt issuance costs						(4,529)		(5,957)
Capital lease payments						(141,750)		(110,202)
Employee Stock Ownership Plan						(7,541)		(1,559)
Securitization deposits						371		448
Common stock dividends paid						(39,171)		(78,374)
Investment contract deposits						180,554		232,912
Investment contract withdrawals						(64,459)		(41,258)
Net cash provided by (used in) financing activities						212,938		223,982
Effects of exchange rate on cash						(16,117)		(17,578)
Increase (decrease) in cash and cash equivalents						383,539		232,777
Cash and cash equivalents at the beginning of period						600,646		441,850
Cash and cash equivalents at the end of the period		984,185		674,627		984,185		674,627
Operating Segments [Member] | Moving and Storage Consolidations [Member]
Cash flow from operating activities:
Net earnings		65,228		81,769		388,876		436,433
Earnings from consolidated entities						(25,925)		(25,219)
Adjustments to reconcile net earnings to cash provided by operations:
Depreciation						354,183		287,562
Amortization of deferred policy acquisition costs
Amortization of debt issuance costs						3,125		2,319
Interest credited to policyholders
Change in allowance for losses on trade receivables						22		29
Change in allowance for inventory reserves						1,897		(1,939)
Net gain on sale of real and personal property						(32,775)		(87,789)
Net (gain) loss on sale of investments
Deferred income tax						114,017		145,104
Net change in other operating assets and liabilities:
Reinsurance recoverables and trade receivables						(24,147)		(5,420)
Inventories						(1,901)		(3,887)
Prepaid expenses						79,578		(57,015)
Capitalization of deferred policy acquisition costs
Other assets						(3,953)		16,907
Related party assets						(5,906)		49,512
Accounts payable and accrued expenses						22,313		16,703
Policy benefits and losses, claims and loss expenses payable						11,805		20,712
Other policyholders' funds and liabilities
Deferred income						1,105		1,005
Related party liabilities						(1,018)		(752)
Net cash provided by operating activities						881,296		794,265
Cash flow from investing activities:
Property, plant and equipment						(981,316)		(1,051,830)
Short term investments
Fixed maturities investments
Equity securities
Preferred stock
Real estate						(3,510)
Mortgage loans						(9,738)		(15,104)
Proceeds from sale of:
Property, plant and equipment						412,892		463,602
Short term investments
Fixed maturities investments
Equity securities
Preferred stock
Real estate
Mortgage loans						4,986		11,635
Net cash used by investing activities						(576,686)		(591,697)
Cash flow from financing activities:
Borrowings from credit facilities						507,008		461,276
Principal repayments on credit facilities						(217,545)		(233,304)
Debt issuance costs						(4,529)		(5,957)
Capital lease payments						(141,750)		(110,202)
Employee Stock Ownership Plan						(7,541)		1,559
Securitization deposits						371		448
Common stock dividends paid						(39,171)		78,374
Investment contract deposits
Investment contract withdrawals
Net cash provided by (used in) financing activities						96,843		32,328
Effects of exchange rate on cash						(16,117)		(17,578)
Increase (decrease) in cash and cash equivalents						385,336		217,318
Cash and cash equivalents at the beginning of period						585,666		431,873
Cash and cash equivalents at the end of the period		971,002		649,191		971,002		649,191
Operating Segments [Member] | Property and Casualty Insurance [Member]
Cash flow from operating activities:
Net earnings		4,731	[1]	4,076	[2]	14,296	[3]	12,229	[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 real and personal property							[3]		[4]
Net (gain) loss on sale of investments						(2,717)	[3]	(652)	[4]
Deferred income tax						(549)	[3]	5,321	[4]
Net change in other operating assets and liabilities:
Reinsurance recoverables and trade receivables						2,388	[3]	12,077	[4]
Inventories							[3]		[4]
Prepaid expenses							[3]		[4]
Capitalization of deferred policy acquisition costs							[3]		[4]
Other assets						2,439	[3]	1,358	[4]
Related party assets						437	[3]	291	[4]
Accounts payable and accrued expenses						2,363	[3]	822	[4]
Policy benefits and losses, claims and loss expenses payable						(5,650)	[3]	(15,402)	[4]
Other policyholders' funds and liabilities						1,024	[3]	(1,239)	[4]
Deferred income							[3]		[4]
Related party liabilities						371	[3]	(169)	[4]
Net cash provided by operating activities						14,402	[3]	14,636	[4]
Cash flow from investing activities:
Property, plant and equipment							[3]		[4]
Short term investments						(67,094)	[3]	(30,536)	[4]
Fixed maturities investments						(22,138)	[3]	(32,593)	[4]
Equity securities							[3]		[4]
Preferred stock	[4]							(5)
Real estate						(4,648)	[3]	(6)	[4]
Mortgage loans						(16,686)	[3]	(1,800)	[4]
Proceeds from sale of:
Property, plant and equipment							[3]		[4]
Short term investments						59,583	[3]	31,816	[4]
Fixed maturities investments						20,697	[3]	19,428	[4]
Equity securities	[4]
Preferred stock						3,351
Real estate
Mortgage loans						9,742		4,447	[4]
Net cash used by investing activities						(17,193)		(9,249)	[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]
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						(2,791)	[3]	5,387	[4]
Cash and cash equivalents at the beginning of period						14,049	[7]	8,495	[4]
Cash and cash equivalents at the end of the period		11,258	[8]	13,882	[4]	11,258	[8]	13,882	[4]
Operating Segments [Member] | Life Insurance [Member]
Cash flow from operating activities:
Net earnings		4,315	[1]	5,014	[2]	11,629	[3]	12,990	[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		5,200	[1]	5,138	[2]	19,131	[5]	15,559	[6]
Amortization of debt issuance costs
Interest credited to policyholders						18,190		13,844
Change in allowance for losses on trade receivables						(50)	[3]	(211)	[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						(1,231)	[3]	(3,127)	[4]
Deferred income tax						(1,020)	[3]	974	[4]
Net change in other operating assets and liabilities:
Reinsurance recoverables and trade receivables						(2,160)	[3]	1,911	[4]
Inventories							[3]		[4]
Prepaid expenses							[3]		[4]
Capitalization of deferred policy acquisition costs						(21,040)	[3]	(24,803)	[4]
Other assets						83	[3]	96	[4]
Related party assets							[3]		[4]
Accounts payable and accrued expenses						6,097	[3]	19,798	[4]
Policy benefits and losses, claims and loss expenses payable						6,688	[3]	7,666	[4]
Other policyholders' funds and liabilities						(1,406)	[3]	679	[4]
Deferred income							[3]		[4]
Related party liabilities						(64)	[3]	43	[4]
Net cash provided by operating activities						34,847	[3]	45,419	[4]
Cash flow from investing activities:
Property, plant and equipment							[3]		[4]
Short term investments						(499,277)	[3]	(361,147)	[4]
Fixed maturities investments						(239,713)	[3]	(286,071)	[4]
Equity securities						(489)	[3]	(1,315)	[4]
Preferred stock	[4]
Real estate						(7,705)	[3]	(17)	[4]
Mortgage loans						(132,885)	[3]	(82,645)	[4]
Proceeds from sale of:
Property, plant and equipment							[3]		[4]
Short term investments						507,372	[3]	369,028	[4]
Fixed maturities investments						126,536	[3]	116,299	[4]
Equity securities	[4]							808
Preferred stock
Real estate						1,681
Mortgage loans						94,532		18,059	[4]
Net cash used by investing activities						(149,948)		(227,001)	[4]
Cash flow from financing activities:
Borrowings from credit facilities						27,000	[3]	47,000	[4]
Principal repayments on credit facilities						(27,000)	[3]	(47,000)	[4]
Debt issuance costs							[3]		[4]
Capital lease payments							[3]		[4]
Employee Stock Ownership Plan							[3]		[4]
Securitization deposits							[3]
Common stock dividends paid							[3]
Investment contract deposits						180,554	[3]	232,912	[4]
Investment contract withdrawals						(64,459)	[3]	(41,258)	[4]
Net cash provided by (used in) financing activities						116,095	[3]	191,654	[4]
Effects of exchange rate on cash							[3]		[4]
Increase (decrease) in cash and cash equivalents						994	[3]	10,072	[4]
Cash and cash equivalents at the beginning of period						931	[7]	1,482	[4]
Cash and cash equivalents at the end of the period		1,925	[8]	11,554	[4]	1,925	[8]	11,554	[4]
Consolidation, Eliminations [Member]
Cash flow from operating activities:
Net earnings		(9,046)		(9,090)		(25,925)		(25,219)
Earnings from consolidated entities						25,925		25,219
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									[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:
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
Equity securities
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, 2016

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

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

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

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

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

[7] Balances as of December 31, 2015

[8] Balances as of September 30, 2016

[9] Elimination of intercompany investments