Consolidating financial information by industry segment (Cash Flow Statements) (Details) - USD ($) $ in Thousands		3 Months Ended				9 Months Ended
		Dec. 31, 2018		Dec. 31, 2017		Dec. 31, 2018		Dec. 31, 2017
Cash flow from operating activities:
Net earnings		$ 78,635		$ 528,894		$ 370,026		$ 779,740
Earnings from consolidated entities
Adjustments to reconcile net earnings to cash provided by operations:
Depreciation						431,652		410,800
Amortization of deferred policy acquisition costs		6,654		5,952		18,584		18,217
Amortization of debt issuance costs						2,922		2,910
Interest credited to policyholders						28,540		23,250
Change in allowance for losses on trade receivables						124		(25)
Change in allowance for inventory reserves						2,539		4,334
Net gain on sale of personal property		(796)		(4,235)		(29,127)		(14,260)
Net gains on disposal of real estate				(192,404)		10		(192,223)
Net (gain) loss on sale of investments						(3,594)		(4,250)
Deferred income tax						108,614		(179,047)
Net change in other operating assets and liabilities:
Reinsurance recoverables and trade receivables						1,601		(27,659)
Inventories						(8,858)		(17,410)
Prepaid expenses						(12,533)		(22,220)
Capitalization of deferred policy acquisition costs						(19,994)		(21,501)
Other assets						159,125		6,279
Related party assets						(1,838)		47,804
Accounts payable and accrued expenses						(5,420)		26,764
Policy benefits and losses, claims and loss expenses payable						(159,285)		2,767
Other policyholders' funds and liabilities						2,867		590
Deferred income						(4,982)		(1,297)
Related party liabilities						(3,269)		(4,542)
Net cash provided by operating activities						877,704		839,021
Cash flow from investing activities:
Escrow Deposits						(3,292)		19,707
Purchases of:
Property, plant and equipment						(1,325,365)		(970,472)
Short term investments						(39,494)		(48,743)
Fixed maturities investments						(394,266)		(274,283)
Equity securities						(957)		(662)
Preferred stock						(81)		(1,000)
Real estate						(505)		(1,783)
Mortgage loans						(56,892)		(80,707)
Proceeds from sale of:
Property, plant and equipment						561,848		591,040
Short term investments						47,012		54,319
Fixed maturities investments						83,767		102,404
Equity securities						8,608
Preferred stock						1,625		3,188
Real estate								5,348
Mortgage loans						116,800		23,726
Net cash used by investing activities						(1,001,192)		(577,918)
Cash flow from financing activities:
Borrowings from credit facilities						693,132		426,262
Principal repayments on credit facilities						(255,123)		(303,212)
Debt issuance costs						(5,097)		(4,581)
Capital lease payments						(236,683)		(219,623)
Employee stock ownership plan		(303)		(2,804)		(203)		(6,764)
Securitization deposits								(2,181)
Common stock dividends paid						(29,385)		(19,587)
Investment contract deposits						300,920		347,695
Investment contract withdrawals						(109,641)		(163,499)
Net cash provided by (used in) financing activities						357,920		54,510
Effects of exchange rate on cash						(9,435)		9,468
Increase (decrease) in cash and cash equivalents						224,997		325,081
Cash and cash equivalents at the beginning of period						759,388		697,806
Cash and cash equivalents at the end of the period		984,385		1,022,887		984,385		1,022,887
Operating Segments [Member] | Moving and Storage Consolidations [Member]
Cash flow from operating activities:
Net earnings		78,635		528,894		370,026		779,740
Earnings from consolidated entities						(30,306)		(25,998)
Adjustments to reconcile net earnings to cash provided by operations:
Depreciation						431,652		410,800
Amortization of deferred policy acquisition costs
Amortization of debt issuance costs						2,922		2,910
Interest credited to policyholders
Change in allowance for losses on trade receivables						129		(22)
Change in allowance for inventory reserves						2,539		4,334
Net gain on sale of personal property						(29,127)		(14,260)
Net gains on disposal of real estate				(192,404)		10		(192,223)
Net (gain) loss on sale of investments
Deferred income tax						108,618		(176,566)
Net change in other operating assets and liabilities:
Reinsurance recoverables and trade receivables						2,323		(32,898)
Inventories						(8,858)		(17,410)
Prepaid expenses						(12,533)		(22,220)
Capitalization of deferred policy acquisition costs
Other assets						159,232		4,649
Related party assets						(1,428)		43,822
Accounts payable and accrued expenses						(16,639)		15,455
Policy benefits and losses, claims and loss expenses payable						(157,470)		8,427
Other policyholders' funds and liabilities
Deferred income						(4,982)		(1,297)
Related party liabilities						(3,039)		(4,412)
Net cash provided by operating activities						813,069		782,831
Cash flow from investing activities:
Escrow Deposits						(3,292)		19,707
Purchases of:
Property, plant and equipment						(1,325,365)		(970,472)
Short term investments
Fixed maturities investments
Equity securities
Preferred stock
Real estate						(236)		(1,637)
Mortgage loans
Proceeds from sale of:
Property, plant and equipment						561,848		591,040
Short term investments
Fixed maturities investments
Equity securities
Preferred stock
Real estate								5,348
Mortgage loans
Net cash used by investing activities						(767,045)		(356,014)
Cash flow from financing activities:
Borrowings from credit facilities						666,232		426,262
Principal repayments on credit facilities						(228,223)		(303,212)
Debt issuance costs						(5,097)		(4,581)
Capital lease payments						(236,683)		(219,623)
Employee stock ownership plan						(203)		(6,764)
Securitization deposits								(2,181)
Common stock dividends paid						(29,385)		19,587
Investment contract deposits
Investment contract withdrawals
Net cash provided by (used in) financing activities						166,641		(129,686)
Effects of exchange rate on cash						(9,435)		9,468
Increase (decrease) in cash and cash equivalents						203,230		306,599
Cash and cash equivalents at the beginning of period						702,036		671,665
Cash and cash equivalents at the end of the period		905,266		978,264		905,266		978,264
Operating Segments [Member] | Property and Casualty Insurance [Member]
Cash flow from operating activities:
Net earnings		8,815	[1]	5,067	[2]	17,214	[3]	12,637	[4]
Earnings from consolidated entities							[5]		[6]
Adjustments to reconcile net earnings to cash provided by operations:
Depreciation							[5]		[6]
Amortization of deferred policy acquisition costs			[1]		[2]		[3]		[4]
Amortization of debt issuance costs							[5]		[6]
Interest credited to policyholders							[5]		[6]
Change in allowance for losses on trade receivables							[5]		[6]
Change in allowance for inventory reserves							[5]		[6]
Net gain on sale of personal property							[5]		[6]
Net gains on disposal of real estate			[1]		[2]		[3]		[4]
Net (gain) loss on sale of investments						(3,007)	[5]	(881)	[6]
Deferred income tax						3,624	[5]	(1,315)	[6]
Net change in other operating assets and liabilities:
Reinsurance recoverables and trade receivables						2,000	[5]	6,908	[6]
Inventories							[5]		[6]
Prepaid expenses							[5]		[6]
Capitalization of deferred policy acquisition costs							[5]		[6]
Other assets						391	[5]	1,796	[6]
Related party assets						(410)	[5]	3,982	[6]
Accounts payable and accrued expenses						1,174	[5]	1,229	[6]
Policy benefits and losses, claims and loss expenses payable						(4,751)	[5]	(6,896)	[6]
Other policyholders' funds and liabilities						(327)	[5]	1,099	[6]
Deferred income							[5]		[6]
Related party liabilities						318	[5]	(205)	[6]
Net cash provided by operating activities						16,226	[5]	18,354	[6]
Cash flow from investing activities:
Escrow Deposits							[5]		[6]
Purchases of:
Property, plant and equipment							[5]		[6]
Short term investments						(39,251)	[5]	(39,701)	[6]
Fixed maturities investments						(32,862)	[5]	(34,284)	[6]
Equity securities							[5]		[6]
Preferred stock							[5]	(1,000)	[6]
Real estate						(187)	[5]	(16)	[6]
Mortgage loans						(13,312)	[5]	(11,609)	[6]
Proceeds from sale of:
Property, plant and equipment							[5]		[6]
Short term investments						47,012	[5]	43,570	[6]
Fixed maturities investments						9,886	[5]	17,821	[6]
Equity securities	[5]					8,608
Preferred stock						1,625	[5]	3,188	[6]
Real estate							[5]		[6]
Mortgage loans						1,331	[5]	3,248	[6]
Net cash used by investing activities						(17,150)	[5]	(18,783)	[6]
Cash flow from financing activities:
Borrowings from credit facilities							[5]		[6]
Principal repayments on credit facilities							[5]		[6]
Debt issuance costs							[5]		[6]
Capital lease payments							[5]		[6]
Employee stock ownership plan							[5]		[6]
Securitization deposits							[5]		[6]
Common stock dividends paid							[5]		[6]
Investment contract deposits							[5]		[6]
Investment contract withdrawals							[5]		[6]
Net cash provided by (used in) financing activities							[5]		[6]
Effects of exchange rate on cash							[5]		[6]
Increase (decrease) in cash and cash equivalents						(924)	[5]	(429)	[6]
Cash and cash equivalents at the beginning of period						6,639	[7]	12,725	[6]
Cash and cash equivalents at the end of the period		5,715	[8]	12,296	[6]	5,715	[8]	12,296	[6]
Operating Segments [Member] | Life Insurance [Member]
Cash flow from operating activities:
Net earnings		5,849	[1]	6,756	[2]	13,092	[3]	13,361	[4]
Earnings from consolidated entities							[5]		[6]
Adjustments to reconcile net earnings to cash provided by operations:
Depreciation							[5]		[6]
Amortization of deferred policy acquisition costs		6,654	[1]	5,952	[2]	18,584	[3]	18,217	[4]
Amortization of debt issuance costs							[5]		[6]
Interest credited to policyholders						28,540	[5]	23,250	[6]
Change in allowance for losses on trade receivables						(5)	[5]	(3)	[6]
Change in allowance for inventory reserves							[5]		[6]
Net gain on sale of personal property							[5]		[6]
Net gains on disposal of real estate			[1]		[2]		[3]		[4]
Net (gain) loss on sale of investments						(587)	[5]	(3,369)	[6]
Deferred income tax						(3,628)	[5]	(1,166)	[6]
Net change in other operating assets and liabilities:
Reinsurance recoverables and trade receivables						(2,722)	[5]	(1,669)	[6]
Inventories							[5]		[6]
Prepaid expenses							[5]		[6]
Capitalization of deferred policy acquisition costs						(19,994)	[5]	(21,501)	[6]
Other assets						(498)	[5]	(166)	[6]
Related party assets							[5]		[6]
Accounts payable and accrued expenses						10,045	[5]	10,080	[6]
Policy benefits and losses, claims and loss expenses payable						2,936	[5]	1,236	[6]
Other policyholders' funds and liabilities						3,194	[5]	(509)	[6]
Deferred income							[5]		[6]
Related party liabilities						(548)	[5]	75	[6]
Net cash provided by operating activities						48,409	[5]	37,836	[6]
Cash flow from investing activities:
Escrow Deposits							[5]		[6]
Purchases of:
Property, plant and equipment							[5]		[6]
Short term investments						(243)	[5]	(9,042)	[6]
Fixed maturities investments						(361,404)	[5]	(239,999)	[6]
Equity securities						(957)	[5]	(662)	[6]
Preferred stock						(81)	[5]		[6]
Real estate						(82)	[5]	(130)	[6]
Mortgage loans						(43,580)	[5]	(69,098)	[6]
Proceeds from sale of:
Property, plant and equipment							[5]		[6]
Short term investments							[5]	10,749	[6]
Fixed maturities investments						73,881	[5]	84,583	[6]
Equity securities	[5]
Preferred stock							[5]		[6]
Real estate							[5]		[6]
Mortgage loans						115,469	[5]	20,478	[6]
Net cash used by investing activities						(216,997)	[5]	(203,121)	[6]
Cash flow from financing activities:
Borrowings from credit facilities						26,900	[5]		[6]
Principal repayments on credit facilities						(26,900)	[5]		[6]
Debt issuance costs							[5]		[6]
Capital lease payments							[5]		[6]
Employee stock ownership plan							[5]		[6]
Securitization deposits							[5]		[6]
Common stock dividends paid							[5]		[6]
Investment contract deposits						300,920	[5]	347,695	[6]
Investment contract withdrawals						(109,641)	[5]	(169,499)	[6]
Net cash provided by (used in) financing activities						191,279	[5]	184,196	[6]
Effects of exchange rate on cash							[5]		[6]
Increase (decrease) in cash and cash equivalents						22,691	[5]	18,911	[6]
Cash and cash equivalents at the beginning of period						50,713	[7]	13,416	[6]
Cash and cash equivalents at the end of the period		73,404	[8]	32,327	[6]	73,404	[8]	32,327	[6]
Consolidation, Eliminations [Member]
Cash flow from operating activities:
Net earnings		(14,664)		(11,823)		(30,306)		(25,998)
Earnings from consolidated entities						30,306		25,998
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
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, 2018

[2] Balances for the quarter ended September 30, 2017

[3] Balances for the nine months ended September 30, 2018

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

[5] Balance for the period ended September 30, 2018

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

[7] Balances as of December 31, 2017

[8] Balances as of September 30, 2018

[9] Elimination of intercompany investments