Consolidating financial information by industry segment (Cash Flow Statements) (Details) - USD ($) $ in Thousands		3 Months Ended
		Jun. 30, 2018		Jun. 30, 2017
Cash flow from operating activities:
Net earnings		$ 127,849		$ 126,207
Earnings from consolidated entities
Adjustments to reconcile net earnings to cash provided by operations:
Depreciation		142,722		131,423
Amortization of deferred policy acquisition costs		6,031		6,321
Amortization of debt issuance costs		984		932
Interest credited to policyholders		8,060		7,651
Change in allowance for losses on trade receivables		38		(26)
Change in allowance for inventory reserves		2,139		1,114
Net gain on sale of real and personal property		(16,295)		(5,088)
Net losses on disposal of real estate				347
Net (gain) loss on sale of investments		506		(1,985)
Deferred income tax		38,678		12,024
Net change in other operating assets and liabilities:
Reinsurance recoverables and trade receivables		(14,543)		(8,870)
Inventories		(7,170)		(11,982)
Prepaid expenses		(17,999)		44,788
Capitalization of deferred policy acquisition costs		(5,808)		(8,228)
Other assets		(761)		(2,523)
Related party assets		2,205		7,836
Accounts payable and accrued expenses		89,348		61,704
Policy benefits and losses, claims and loss expenses payable		5,291		4,747
Other policyholders' funds and liabilities		(184)		4,083
Deferred income		7,732		8,393
Related party liabilities		474		(2,532)
Net cash provided by operating activities		369,297		376,336
Cash flow from investing activities:
Escrow deposits		(4,559)		23,005
Purchase of:
Property, plant and equipment		(584,147)		(480,259)
Short term investments		(14,390)		(16,491)
Fixed maturity investments		(103,121)		(123,090)
Equity securities		(46)
Preferred stock		(81)
Real estate		(80)		(505)
Mortgage loans		(8,262)		(24,382)
Proceeds from sale of:
Property, plant and equipment		187,546		142,343
Short term investments		20,416		24,639
Fixed maturity investments		14,946		36,559
Preferred stock		500
Real estate				2,664
Mortgage loans		9,402		6,054
Net cash used by investing activities		(445,876)		(409,463)
Cash flow from financing activities:
Borrowings from credit facilities		103,641		155,367
Principal repayments on credit facilities		(73,770)		(64,819)
Payment of debt issuance costs		(1,420)		(1,734)
Capital lease payments		(84,374)		(56,522)
Employee stock ownership plan shares		(57)		3,516
Securitization deposits				49
Common stock dividends paid		(9,795)
Investment contract deposits		76,343		155,437
Investment contract withdrawals		(38,763)		(54,205)
Net cash provided by (used in) financing activities		(28,195)		137,089
Effects of exchange rate on cash		(4,275)		4,424
Increase (decrease) in cash and cash equivalents		(109,049)		108,386
Cash and cash equivalents at the beginning of period		759,388		697,806
Cash and cash equivalents at the end of the period		650,339		806,192
Operating Segments [Member] | Moving and Storage Consolidations [Member]
Cash flow from operating activities:
Net earnings		127,849		126,207
Earnings from consolidated entities		(3,656)		(5,810)
Adjustments to reconcile net earnings to cash provided by operations:
Depreciation		142,722		131,423
Amortization of deferred policy acquisition costs
Amortization of debt issuance costs		984		932
Interest credited to policyholders
Change in allowance for losses on trade receivables		40		(26)
Change in allowance for inventory reserves		2,139		1,114
Net gain on sale of real and personal property		(16,295)		(5,088)
Net losses on disposal of real estate				347
Net (gain) loss on sale of investments
Deferred income tax		38,011		16,765
Net change in other operating assets and liabilities:
Reinsurance recoverables and trade receivables		(14,763)		(10,955)
Inventories		(7,170)		(11,982)
Prepaid expenses		(17,999)		44,788
Capitalization of deferred policy acquisition costs
Other assets		(132)		(4,098)
Related party assets		4,713		7,721
Accounts payable and accrued expenses		84,004		48,255
Policy benefits and losses, claims and loss expenses payable		4,208		7,125
Other policyholders' funds and liabilities
Deferred income		7,732		8,393
Related party liabilities		(913)		(2,812)
Net cash provided by operating activities		351,474		352,299
Cash flow from investing activities:
Escrow deposits		(4,559)		23,005
Purchase of:
Property, plant and equipment		(548,147)		(480,259)
Short term investments
Fixed maturity investments
Equity securities
Preferred stock
Real estate				(505)
Mortgage loans
Proceeds from sale of:
Property, plant and equipment		187,546		142,343
Short term investments
Fixed maturity investments
Preferred stock
Real estate				2,664
Mortgage loans
Net cash used by investing activities		(365,160)		(312,752)
Cash flow from financing activities:
Borrowings from credit facilities		103,641		155,367
Principal repayments on credit facilities		(73,770)		(64,819)
Payment of debt issuance costs		(1,420)		(1,734)
Capital lease payments		(84,374)		(56,522)
Employee stock ownership plan shares		(57)		3,516
Securitization deposits				49
Common stock dividends paid		(9,795)
Investment contract deposits
Investment contract withdrawals
Net cash provided by (used in) financing activities		(65,775)		35,857
Effects of exchange rate on cash		(4,275)		4,424
Increase (decrease) in cash and cash equivalents		(83,736)		79,828
Cash and cash equivalents at the beginning of period		702,036		671,665
Cash and cash equivalents at the end of the period		618,300		751,493
Operating Segments [Member] | Property and Casualty Insurance [Member]
Cash flow from operating activities:
Net earnings		2,168	[1]	3,574	[2]
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]
Amortization of debt issuance costs			[3]		[4]
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 losses on disposal of real estate
Net (gain) loss on sale of investments		(38)	[3]	(589)	[4]
Deferred income tax		1,140	[3]	(1,600)	[4]
Net change in other operating assets and liabilities:
Reinsurance recoverables and trade receivables		2,331	[3]	4,375	[4]
Inventories			[3]		[4]
Prepaid expenses			[3]		[4]
Capitalization of deferred policy acquisition costs			[3]		[4]
Other assets		(243)	[3]	1,665	[4]
Related party assets		(2,508)	[3]	115	[4]
Accounts payable and accrued expenses		835	[3]	1,249	[4]
Policy benefits and losses, claims and loss expenses payable		(1,466)	[3]	(6,051)	[4]
Other policyholders' funds and liabilities		(577)	[3]	101	[4]
Deferred income			[3]		[4]
Related party liabilities		2,003	[3]	(117)	[4]
Net cash provided by operating activities		3,645	[3]	2,722	[4]
Cash flow from investing activities:
Escrow deposits
Purchase of:
Property, plant and equipment			[3]		[4]
Short term investments		(14,220)	[3]	(10,779)	[4]
Fixed maturity investments		(12,754)	[3]	(11,602)	[4]
Equity securities
Preferred stock
Real estate		(59)	[3]		[4]
Mortgage loans		(2,287)	[3]	(6,059)	[4]
Proceeds from sale of:
Property, plant and equipment			[3]		[4]
Short term investments		20,287	[3]	15,424	[4]
Fixed maturity investments		3,170	[3]	4,275	[4]
Preferred stock	[3]	500
Real estate
Mortgage loans		198	[3]	1,585
Net cash used by investing activities		(5,165)	[3]	(7,156)
Cash flow from financing activities:
Borrowings from credit facilities			[3]		[4]
Principal repayments on credit facilities			[3]		[4]
Payment of debt issuance costs			[3]
Capital lease payments			[3]		[4]
Employee stock ownership plan shares
Securitization deposits
Common stock dividends paid
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		(1,520)	[3]	(4,434)	[4]
Cash and cash equivalents at the beginning of period		6,639	[5]	12,725
Cash and cash equivalents at the end of the period		5,119	[6]	8,291
Operating Segments [Member] | Life Insurance [Member]
Cash flow from operating activities:
Net earnings		1,488	[1]	2,236	[2]
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		6,031	[1]	6,321	[2]
Amortization of debt issuance costs			[3]		[4]
Interest credited to policyholders		8,060		7,651
Change in allowance for losses on trade receivables		(2)	[3]		[4]
Change in allowance for inventory reserves			[3]		[4]
Net gain on sale of real and personal property			[3]		[4]
Net losses on disposal of real estate
Net (gain) loss on sale of investments		544	[3]	(1,396)	[4]
Deferred income tax		(473)	[3]	(3,141)	[4]
Net change in other operating assets and liabilities:
Reinsurance recoverables and trade receivables		(2,111)	[3]	(2,290)	[4]
Inventories			[3]		[4]
Prepaid expenses			[3]		[4]
Capitalization of deferred policy acquisition costs		(5,808)	[3]	(8,228)	[4]
Other assets		(386)	[3]	(90)	[4]
Related party assets			[3]		[4]
Accounts payable and accrued expenses		4,509	[3]	12,200	[4]
Policy benefits and losses, claims and loss expenses payable		2,549	[3]	3,673	[4]
Other policyholders' funds and liabilities		393	[3]	3,982	[4]
Deferred income			[3]		[4]
Related party liabilities		(616)	[3]	397	[4]
Net cash provided by operating activities		14,178	[3]	21,315	[4]
Cash flow from investing activities:
Escrow deposits
Purchase of:
Property, plant and equipment			[3]		[4]
Short term investments		(170)	[3]	(5,712)	[4]
Fixed maturity investments		(90,367)	[3]	(111,488)	[4]
Equity securities		(46)
Preferred stock		(81)
Real estate		(21)	[3]		[4]
Mortgage loans		(5,975)	[3]	(18,323)	[4]
Proceeds from sale of:
Property, plant and equipment			[3]		[4]
Short term investments		129	[3]	9,215	[4]
Fixed maturity investments		11,776	[3]	32,284	[4]
Preferred stock	[3]
Real estate
Mortgage loans		9,204	[3]	4,469
Net cash used by investing activities		(75,551)	[3]	(89,555)
Cash flow from financing activities:
Borrowings from credit facilities			[3]		[4]
Principal repayments on credit facilities			[3]		[4]
Payment of debt issuance costs			[3]
Capital lease payments			[3]		[4]
Employee stock ownership plan shares
Securitization deposits
Common stock dividends paid
Investment contract deposits		76,343	[3]	155,437	[4]
Investment contract withdrawals		(38,763)	[3]	(54,205)	[4]
Net cash provided by (used in) financing activities		37,580	[3]	101,232	[4]
Effects of exchange rate on cash			[3]		[4]
Increase (decrease) in cash and cash equivalents		(23,793)	[3]	32,992	[4]
Cash and cash equivalents at the beginning of period		50,713	[5]	13,416
Cash and cash equivalents at the end of the period		26,920	[6]	46,408
Consolidation, Eliminations [Member]
Cash flow from operating activities:
Net earnings		(3,656)		(5,810)
Earnings from consolidated entities		3,656		5,810
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 losses 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
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:
Escrow deposits
Purchase of:
Property, plant and equipment
Short term investments
Fixed maturity investments
Equity securities
Preferred stock
Real estate
Mortgage loans
Proceeds from sale of:
Property, plant and equipment
Short term investments
Fixed maturity 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
Payment of debt issuance costs
Capital lease payments
Employee stock ownership plan shares
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 March 31, 2018

[2] Balances for the quarter ended March 31, 2017

[3] Balance for the period ended March 31, 2018

[4] Balance for the period ended March 31, 2017

[5] Balances as of December 31, 2017

[6] Balances as of March 31, 2018