Consolidating financial information by industry segment (Cash Flow Statements) (Details) - USD ($) $ in Thousands	3 Months Ended
	Jun. 30, 2017		Jun. 30, 2016
Cash flow from operating activities:
Net earnings	$ 126,207		$ 147,173
Earnings from consolidated entities
Adjustments to reconcile net earnings to cash provided by operations:
Depreciation	131,423		114,021
Amortization of deferred policy acquisition costs	6,321		7,942
Amortization of debt issuance costs	932		961
Interest credited to policyholders	7,651		5,059
Change in allowance for losses on trade receivables	(26)		21
Change in allowance for inventory reserves	1,114		1,221
Net gain on sale of real and personal property	(4,741)		(18,640)
Net (gain) loss on sale of investments	(1,985)		(2,406)
Deferred income tax	12,024		22,733
Net change in other operating assets and liabilities:
Reinsurance recoverables and trade receivables	(8,870)		(14,138)
Inventories	(11,982)		(4,391)
Prepaid expenses	44,788		39,828
Capitalization of deferred policy acquisition costs	(8,228)		(7,252)
Other assets	17,812		(3,392)
Related party assets	7,836		4,084
Accounts payable and accrued expenses	61,704		57,099
Policy benefits and losses, claims and loss expenses payable	4,747		1,373
Other policyholders' funds and liabilities	4,083		242
Deferred income	8,393		8,727
Related party liabilities	(2,532)		781
Net cash provided by operating activities	396,671		361,046
Cash flow from investing activities:
Property, plant and equipment	(480,259)		(437,287)
Short term investments	(16,491)		(277,038)
Fixed maturity investments	(123,090)		(166,648)
Real estate	(505)		(3,495)
Mortgage loans	(24,382)		(62,572)
Proceeds from sale of:
Property, plant and equipment	142,343		147,196
Short term investments	24,639		279,341
Fixed maturity investments	36,559		55,946
Preferred stock			2,000
Real estate	2,664		831
Mortgage loans	6,054		94,015
Net cash used by investing activities	(432,468)		(367,711)
Cash flow from financing activities:
Borrowings from credit facilities	155,367		103,338
Principal repayments on credit facilities	(64,819)		(48,326)
Debt issuance costs	(1,734)		(223)
Capital lease payments	(56,522)		(37,405)
Employee stock ownership plan	3,516		(1,393)
Securitization deposits	49		93
Common stock dividends paid			(19,586)
Investment contract deposits	155,437		74,157
Investment contract withdrawals	(54,205)		(14,051)
Net cash provided by (used in) financing activities	137,089		56,604
Effects of exchange rate on cash	4,424		(4,397)
Increase (decrease) in cash and cash equivalents	105,716		45,542
Cash and cash equivalents at the beginning of period	697,806		600,646
Cash and cash equivalents at the end of the period	803,522		646,188
Operating Segments [Member] | Moving and Storage Consolidations [Member]
Cash flow from operating activities:
Net earnings	126,207		147,173
Earnings from consolidated entities	(5,810)		(7,574)
Adjustments to reconcile net earnings to cash provided by operations:
Depreciation	131,423		114,021
Amortization of deferred policy acquisition costs
Amortization of debt issuance costs	932		961
Interest credited to policyholders
Change in allowance for losses on trade receivables	(26)		21
Change in allowance for inventory reserves	1,114		1,221
Net gain on sale of real and personal property	(4,741)		(18,640)
Net (gain) loss on sale of investments
Deferred income tax	16,765		22,401
Net change in other operating assets and liabilities:
Reinsurance recoverables and trade receivables	(10,955)		(10,746)
Inventories	(11,982)		(4,391)
Prepaid expenses	44,788		39,828
Capitalization of deferred policy acquisition costs
Other assets	16,237		(5,817)
Related party assets	7,721		3,687
Accounts payable and accrued expenses	48,255		58,699
Policy benefits and losses, claims and loss expenses payable	7,125		(1,600)
Other policyholders' funds and liabilities
Deferred income	8,393		8,727
Related party liabilities	(2,812)		861
Net cash provided by operating activities	372,634		348,832
Cash flow from investing activities:
Property, plant and equipment	(480,259)		(437,287)
Short term investments
Fixed maturity investments
Real estate	(505)		(3,495)
Mortgage loans			(1,838)
Proceeds from sale of:
Property, plant and equipment	142,343		147,196
Short term investments
Fixed maturity investments
Preferred stock
Real estate	2,664
Mortgage loans			3,490
Net cash used by investing activities	(335,757)		(291,934)
Cash flow from financing activities:
Borrowings from credit facilities	155,367		103,338
Principal repayments on credit facilities	(64,819)		(48,326)
Debt issuance costs	(1,734)		(223)
Capital lease payments	(56,522)		(37,405)
Employee stock ownership plan	3,516		(1,393)
Securitization deposits	49		93
Common stock dividends paid			(19,586)
Investment contract deposits
Investment contract withdrawals
Net cash provided by (used in) financing activities	35,857		(3,502)
Effects of exchange rate on cash	4,424		(4,397)
Increase (decrease) in cash and cash equivalents	77,158		48,999
Cash and cash equivalents at the beginning of period	671,665		585,666
Cash and cash equivalents at the end of the period	748,823		634,665
Operating Segments [Member] | Property and Casualty Insurance [Member]
Cash flow from operating activities:
Net earnings	3,574		4,877
Earnings from consolidated entities		[1]		[2]
Adjustments to reconcile net earnings to cash provided by operations:
Depreciation		[1]		[2]
Amortization of deferred policy acquisition costs		[3]		[4]
Amortization of debt issuance costs		[1]		[2]
Interest credited to policyholders
Change in allowance for losses on trade receivables		[1]		[2]
Change in allowance for inventory reserves		[1]		[2]
Net gain on sale of real and personal property		[1]		[2]
Net (gain) loss on sale of investments	(589)	[1]	(2,163)	[2]
Deferred income tax	(1,600)	[1]	(21)	[2]
Net change in other operating assets and liabilities:
Reinsurance recoverables and trade receivables	4,375	[1]	(421)	[2]
Inventories		[1]		[2]
Prepaid expenses		[1]		[2]
Capitalization of deferred policy acquisition costs		[1]		[2]
Other assets	1,665	[1]	2,377	[2]
Related party assets	115	[1]	397	[2]
Accounts payable and accrued expenses	1,249	[1]	(142)	[2]
Policy benefits and losses, claims and loss expenses payable	(6,051)	[1]	(1,746)	[2]
Other policyholders' funds and liabilities	101	[1]	8	[2]
Deferred income		[1]		[2]
Related party liabilities	(117)	[1]	(7)	[2]
Net cash provided by operating activities	2,722	[1]	3,159	[2]
Cash flow from investing activities:
Property, plant and equipment		[1]		[2]
Short term investments	(10,779)	[1]	(18,901)	[2]
Fixed maturity investments	(11,602)	[1]	(13,469)	[2]
Real estate		[1]		[2]
Mortgage loans	(6,059)	[1]	(3,063)	[2]
Proceeds from sale of:
Property, plant and equipment		[1]		[2]
Short term investments	15,424	[1]	11,246	[2]
Fixed maturity investments	4,275	[1]	8,201	[2]
Preferred stock		[1]	2,000
Real estate		[1]
Mortgage loans	1,585	[1]	6,217
Net cash used by investing activities	(7,156)	[1]	(7,769)
Cash flow from financing activities:
Borrowings from credit facilities		[1]		[2]
Principal repayments on credit facilities		[1]		[2]
Debt issuance costs		[1]
Capital lease payments		[1]		[2]
Employee stock ownership plan
Securitization deposits		[1]
Common stock dividends paid
Investment contract deposits		[1]		[2]
Investment contract withdrawals		[1]		[2]
Net cash provided by (used in) financing activities		[1]		[2]
Effects of exchange rate on cash		[1]		[2]
Increase (decrease) in cash and cash equivalents	(4,434)	[1]	(4,610)	[2]
Cash and cash equivalents at the beginning of period	12,725	[5]	14,049
Cash and cash equivalents at the end of the period	8,291	[6]	9,439
Operating Segments [Member] | Life Insurance [Member]
Cash flow from operating activities:
Net earnings	2,236		2,697
Earnings from consolidated entities		[1]		[2]
Adjustments to reconcile net earnings to cash provided by operations:
Depreciation		[1]		[2]
Amortization of deferred policy acquisition costs	6,321	[3]	7,942	[4]
Amortization of debt issuance costs		[1]		[2]
Interest credited to policyholders	7,651		5,059
Change in allowance for losses on trade receivables		[1]		[2]
Change in allowance for inventory reserves		[1]		[2]
Net gain on sale of real and personal property		[1]		[2]
Net (gain) loss on sale of investments	(1,396)	[1]	(243)	[2]
Deferred income tax	(3,141)	[1]	353	[2]
Net change in other operating assets and liabilities:
Reinsurance recoverables and trade receivables	(2,290)	[1]	(2,971)	[2]
Inventories		[1]		[2]
Prepaid expenses		[1]		[2]
Capitalization of deferred policy acquisition costs	(8,228)	[1]	(7,252)	[2]
Other assets	(90)	[1]	48	[2]
Related party assets		[1]		[2]
Accounts payable and accrued expenses	12,200	[1]	(1,458)	[2]
Policy benefits and losses, claims and loss expenses payable	3,673	[1]	4,719	[2]
Other policyholders' funds and liabilities	3,982	[1]	234	[2]
Deferred income		[1]		[2]
Related party liabilities	397	[1]	(73)	[2]
Net cash provided by operating activities	21,315	[1]	9,055	[2]
Cash flow from investing activities:
Property, plant and equipment		[1]		[2]
Short term investments	(5,712)	[1]	(258,137)	[2]
Fixed maturity investments	(111,488)	[1]	(153,179)	[2]
Real estate		[1]		[2]
Mortgage loans	(18,323)	[1]	(57,671)	[2]
Proceeds from sale of:
Property, plant and equipment		[1]		[2]
Short term investments	9,215	[1]	268,095	[2]
Fixed maturity investments	32,284	[1]	47,745	[2]
Preferred stock		[1]
Real estate		[1]	831
Mortgage loans	4,469	[1]	84,308
Net cash used by investing activities	(89,555)	[1]	(68,008)
Cash flow from financing activities:
Borrowings from credit facilities		[1]		[2]
Principal repayments on credit facilities		[1]		[2]
Debt issuance costs		[1]
Capital lease payments		[1]		[2]
Employee stock ownership plan
Securitization deposits		[1]
Common stock dividends paid
Investment contract deposits	155,437	[1]	74,157	[2]
Investment contract withdrawals	(54,205)	[1]	(14,051)	[2]
Net cash provided by (used in) financing activities	101,232	[1]	60,106	[2]
Effects of exchange rate on cash		[1]		[2]
Increase (decrease) in cash and cash equivalents	32,992	[1]	1,153	[2]
Cash and cash equivalents at the beginning of period	13,416	[5]	931
Cash and cash equivalents at the end of the period	46,408	[6]	2,084
Consolidation, Eliminations [Member]
Cash flow from operating activities:
Net earnings	(5,810)		(7,574)
Earnings from consolidated entities	5,810		7,574
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 maturity investments
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
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] Balance for the period ended March 31, 2017

[2] Balance for the period ended March 31, 2016

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

[4] Balances for the quarter ended March 31, 2016

[5] Balances as of December 31, 2016

[6] Balances as of March 31, 2017