Consolidating financial information by industry segment (Cash Flow Statements) (Details) - USD ($) $ in Thousands	12 Months Ended
	Mar. 31, 2016		Mar. 31, 2015		Mar. 31, 2014
Cash flow from operating activities:
Net earnings	$ 489,001		$ 356,741		$ 342,391
Earnings from consolidated subsidiaries
Adjustments to reconcile net earnings to cash provided by operations:
Depreciation	$ 389,393		$ 352,796		$ 293,169
Amortization of deferred policy acquisition costs	23,272		19,661		19,982
Interest credited to policy holders	20,465		18,110		22,890
Change in allowance for losses on trade receivables	(205)		(168)		(36)
Change in allowance for inventory reserves	(1,343)		(872)		871
Net gain on sale of real and personal property	(98,703)		(74,631)		(33,557)
Net gain (loss) on sale of investments	(4,491)		(3,925)		(6,411)
Deferred income taxes	138,075		76,500		46,371
Net change in other operating assets and liabilities:
Reinsurance recoverables and trade receivables	14,765		9,632		62,506
Inventories	(9,009)		(1,579)		(11,495)
Prepaid expenses	(10,338)		(65,720)		2,186
Capitalization of deferred policy acquisition costs	(32,590)		(27,084)		(32,611)
Other assets	15,322		3,735		7,667
Related party assets	56,644		27,706		7,554
Accounts payable and accrued expenses	37,387		98,877		36,365
Policy benefits and losses, claims and loss expenses payable	9,626		(17,621)		(30,496)
Other policyholders' funds and liabilities	(349)		988		631
Deferred income	4,757		(13,181)		1,259
Related party liabilities	(616)		(866)		4,730
Net cash provided by operating activities	1,041,063		759,099		733,966
Cash flow from investing activities:
Property, plant and equipment	(1,509,154)		(1,041,931)		(1,000,243)
Short term investments	(515,899)		(290,379)		(270,690)
Fixed maturities investments	(417,062)		(214,371)		(282,424)
Equity securities	(1,315)		(3,759)		(1,562)
Preferred stock	(1,005)		(2,006)		(640)
Real estate	(75)		(15,399)		(532)
Mortgage loans	(102,588)		(42,683)		(52,419)
Proceeds from sale and paydowns of:
Property, plant and equipment	539,256		411,629		270,053
Short term investments	528,180		287,883		269,052
Fixed maturities investments	154,536		107,867		138,401
Equity securities	2,044		3,082		29,139
Preferred stock	$ 1,126		2,427		6,004
Real estate			396		544
Mortgage loans	$ 48,557		41,983		48,686
Net cash used by investing activities	(1,273,399)		(755,261)		(846,631)
Cash flow from financing activities:
Borrowings from credit facilities	855,972		657,535		431,029
Principal repayments on credit facilities	(428,403)		(593,722)		(293,068)
Debt issuance costs	(10,184)		(12,327)		(3,943)
Capital lease payments	(168,661)		(121,202)		(53,079)
Employee stock ownership plan	(9,302)		$ (7,939)		$ (207)
Securitization deposits	544
Common stock dividends paid	(78,374)		$ (19,594)		$ (19,568)
Investment contract deposits	298,237		105,019		117,723
Investment contract withdrawals	(52,957)		(54,108)		(34,677)
Net cash provided by financing activities	406,872		(46,338)		144,210
Effects of exchange rate on cash	(15,740)		(10,762)		(177)
Increase (decrease) in cash and cash equivalents	158,796		(53,262)		31,368
Cash and cash equivalents at the beginning of period	441,850		495,112		463,744
Cash and cash equivalents at the end of the period	600,646		441,850		495,112
Operating Segments [Member] | Moving and Storage Consolidations [Member]
Cash flow from operating activities:
Net earnings	489,001		356,741		342,391
Earnings from consolidated subsidiaries	(35,522)		(34,783)		(29,992)
Adjustments to reconcile net earnings to cash provided by operations:
Depreciation	$ 389,393		$ 352,796		$ 293,169
Amortization of deferred policy acquisition costs
Interest credited to policy holders
Change in allowance for losses on trade receivables	$ 7		$ (179)		$ (28)
Change in allowance for inventory reserves	(1,343)		(872)		871
Net gain on sale of real and personal property	$ (98,703)		$ (74,631)		(33,557)
Net gain (loss) on sale of investments					(1,325)
Deferred income taxes	$ 124,838		$ 66,628		34,605
Net change in other operating assets and liabilities:
Reinsurance recoverables and trade receivables	(2,169)		(3,213)		14,328
Inventories	(9,009)		(1,579)		(11,495)
Prepaid expenses	$ (10,338)		$ (65,720)		$ 2,186
Capitalization of deferred policy acquisition costs
Other assets	$ 16,231		$ 4,437		$ 8,670
Related party assets	55,962		27,753		11,060
Accounts payable and accrued expenses	26,093		91,409		32,394
Policy benefits and losses, claims and loss expenses payable	$ 23,215		$ (4,327)		$ (8,202)
Other policyholders' funds and liabilities
Deferred income	$ 4,757		$ (13,181)		$ 1,259
Related party liabilities	(779)		(1,016)		5,647
Net cash provided by operating activities	971,634		700,263		661,981
Cash flow from investing activities:
Property, plant and equipment	$ (1,509,154)		$ (1,041,931)		$ (1,000,243)
Short term investments
Fixed maturities investments
Equity securities
Preferred stock
Real estate
Mortgage loans	$ (15,384)		$ (22,876)		$ (21,349)
Proceeds from sale and paydowns of:
Property, plant and equipment	$ 539,256		$ 411,629		$ 270,053
Short term investments
Fixed maturities investments
Equity securities					$ 26,569
Preferred stock
Real estate					$ 193
Mortgage loans	$ 21,589		$ 28,089		38,959
Net cash used by investing activities	(963,693)		(625,089)		(685,818)
Cash flow from financing activities:
Borrowings from credit facilities	808,972		657,535		431,029
Principal repayments on credit facilities	(381,403)		(593,722)		(293,068)
Debt issuance costs	(10,184)		(12,327)		(3,943)
Capital lease payments	(168,661)		(121,202)		(53,079)
Employee stock ownership plan	(9,302)		(7,939)		$ (207)
Securitization deposits	544
Common stock dividends paid	$ (78,374)		$ (19,594)		$ (19,568)
Investment contract deposits
Investment contract withdrawals
Net cash provided by financing activities	$ 161,592		$ (97,249)		$ 61,164
Effects of exchange rate on cash	(15,740)		(10,762)		(177)
Increase (decrease) in cash and cash equivalents	153,793		(32,837)		37,150
Cash and cash equivalents at the beginning of period	431,873		464,710		427,560
Cash and cash equivalents at the end of the period	585,666		431,873		464,710
Operating Segments [Member] | Property and Casualty Insurance [Member]
Cash flow from operating activities:
Net earnings	$ 16,168	[1]	$ 15,417	[2]	$ 12,662	[3]
Earnings from consolidated subsidiaries		[4]		[5]		[6]
Adjustments to reconcile net earnings to cash provided by operations:
Depreciation		[4]		[5]		[6]
Amortization of deferred policy acquisition costs		[1]		[2]		[3]
Interest credited to policy holders		[4]		[5]		[6]
Change in allowance for losses on trade receivables		[4]		[5]		[6]
Change in allowance for inventory reserves		[4]		[5]		[6]
Net gain on sale of real and personal property		[4]		[5]		[6]
Net gain (loss) on sale of investments	$ (1,317)	[4]	$ (841)	[5]	$ (536)	[6]
Deferred income taxes	9,311	[4]	8,030	[5]	7,301	[6]
Net change in other operating assets and liabilities:
Reinsurance recoverables and trade receivables	$ 13,528	[4]	$ 16,830	[5]	$ 43,675	[6]
Inventories		[4]		[5]		[6]
Prepaid expenses		[4]		[5]		[6]
Capitalization of deferred policy acquisition costs		[4]		[5]		[6]
Other assets	$ (1,050)	[4]	$ 102	[5]	$ (781)	[6]
Related party assets	682	[4]	(258)	[5]	(4,231)	[6]
Accounts payable and accrued expenses	1,533	[4]	22	[5]	62	[6]
Policy benefits and losses, claims and loss expenses payable	(18,925)	[4]	(23,472)	[5]	(34,968)	[6]
Other policyholders' funds and liabilities	$ (1,056)	[4]	$ 317	[5]	$ 513	[6]
Deferred income		[4]		[5]		[6]
Related party liabilities	$ 115	[4]	$ 428	[5]	$ (131)	[6]
Net cash provided by operating activities	$ 18,989	[4]	$ 16,575	[5]	$ 23,566	[6]
Cash flow from investing activities:
Property, plant and equipment		[4]		[5]		[6]
Short term investments	$ (44,735)	[4]	$ (40,583)	[5]	$ (60,551)	[6]
Fixed maturities investments	$ (45,048)	[4]	(43,062)	[5]	(58,790)	[6]
Equity securities		[4]	(3,333)	[5]	(746)	[6]
Preferred stock	$ (1,005)	[4]	(1,006)	[5]	$ (640)	[6]
Real estate	(36)	[4]	(7,857)	[5]		[6]
Mortgage loans	$ (1,800)	[4]	$ (4,350)	[5]	$ (3,500)	[6]
Proceeds from sale and paydowns of:
Property, plant and equipment		[4]		[5]		[6]
Short term investments	$ 44,756	[4]	$ 53,112	[5]	$ 68,852	[6]
Fixed maturities investments	26,193	[4]	18,556	[5]	17,106	[6]
Equity securities	1,236	[4]	3,082	[5]	2,570	[6]
Preferred stock	$ 1,126	[4]	$ 400	[5]	$ 4,504	[6]
Real estate		[4]		[5]		[6]
Mortgage loans	$ 5,878	[4]	$ 4,203	[5]	$ 6,267	[6]
Net cash used by investing activities	$ (13,435)	[4]	$ (20,838)	[5]	$ (24,928)	[6]
Cash flow from financing activities:
Borrowings from credit facilities		[4]		[5]		[6]
Principal repayments on credit facilities		[4]		[5]		[6]
Debt issuance costs		[4]		[5]		[6]
Capital lease payments		[4]		[5]		[6]
Employee stock ownership plan		[4]		[5]		[6]
Securitization deposits		[4]				[6]
Common stock dividends paid		[4]		[5]		[6]
Investment contract deposits		[4]		[5]		[6]
Investment contract withdrawals		[4]		[5]		[6]
Net cash provided by financing activities		[4]		[5]		[6]
Effects of exchange rate on cash		[4]		[5]		[6]
Increase (decrease) in cash and cash equivalents	$ 5,554	[4]	$ (4,263)	[5]	$ (1,362)	[6]
Cash and cash equivalents at the beginning of period	8,495	[7]	12,758	[6]	14,120	[6]
Cash and cash equivalents at the end of the period	14,049	[8]	8,495	[7]	12,758	[6]
Operating Segments [Member] | Life Insurance [Member]
Cash flow from operating activities:
Net earnings	$ 19,354	[1]	$ 19,366	[2]	$ 17,330	[3]
Earnings from consolidated subsidiaries		[4]		[5]		[6]
Adjustments to reconcile net earnings to cash provided by operations:
Depreciation		[4]		[5]		[6]
Amortization of deferred policy acquisition costs	$ 23,272	[1]	$ 19,661	[2]	$ 19,982	[3]
Interest credited to policy holders	20,465	[4]	18,110	[5]	22,890	[6]
Change in allowance for losses on trade receivables	$ (212)	[4]	$ 11	[5]	$ (8)	[6]
Change in allowance for inventory reserves		[4]		[5]		[6]
Net gain on sale of real and personal property		[4]		[5]		[6]
Net gain (loss) on sale of investments	$ (3,174)	[4]	$ (3,084)	[5]	$ (4,550)	[6]
Deferred income taxes	3,926	[4]	1,842	[5]	4,465	[6]
Net change in other operating assets and liabilities:
Reinsurance recoverables and trade receivables	$ 3,406	[4]	$ (3,985)	[5]	$ 4,503	[6]
Inventories		[4]		[5]		[6]
Prepaid expenses		[4]		[5]		[6]
Capitalization of deferred policy acquisition costs	$ (32,590)	[4]	$ (27,084)	[5]	$ (32,611)	[6]
Other assets	$ 141	[4]	$ (804)	[5]	$ (222)	[6]
Related party assets		[4]		[5]		[6]
Accounts payable and accrued expenses	$ 9,761	[4]	$ 7,446	[5]	$ 3,909	[6]
Policy benefits and losses, claims and loss expenses payable	5,336	[4]	10,178	[5]	12,674	[6]
Other policyholders' funds and liabilities	$ 707	[4]	$ 671	[5]	$ 118	[6]
Deferred income		[4]		[5]		[6]
Related party liabilities	$ 48	[4]	$ (67)	[5]	$ (61)	[6]
Net cash provided by operating activities	$ 50,440	[4]	$ 42,261	[5]	$ 48,419	[6]
Cash flow from investing activities:
Property, plant and equipment		[4]		[5]		[6]
Short term investments	$ (471,164)	[4]	$ (249,796)	[5]	$ (210,139)	[6]
Fixed maturities investments	(372,014)	[4]	(171,309)	[5]	(223,634)	[6]
Equity securities	$ (1,315)	[4]	(426)	[5]	$ (816)	[6]
Preferred stock		[4]	(1,000)	[5]		[6]
Real estate	$ (39)	[4]	(7,542)	[5]	$ (532)	[6]
Mortgage loans	$ (85,404)	[4]	$ (15,457)	[5]	$ (39,159)	[6]
Proceeds from sale and paydowns of:
Property, plant and equipment		[4]		[5]		[6]
Short term investments	$ 483,424	[4]	$ 234,771	[5]	$ 200,200	[6]
Fixed maturities investments	128,343	[4]	$ 89,311	[5]	$ 121,295	[6]
Equity securities	$ 808	[4]		[5]		[6]
Preferred stock		[4]	$ 2,027	[5]	$ 1,500	[6]
Real estate		[4]	396	[5]	351	[6]
Mortgage loans	$ 21,090	[4]	9,691	[5]	15,049	[6]
Net cash used by investing activities	(296,271)	[4]	$ (109,334)	[5]	$ (135,885)	[6]
Cash flow from financing activities:
Borrowings from credit facilities	47,000	[4]		[5]		[6]
Principal repayments on credit facilities	$ (47,000)	[4]		[5]		[6]
Debt issuance costs		[4]		[5]		[6]
Capital lease payments		[4]		[5]		[6]
Employee stock ownership plan		[4]		[5]		[6]
Securitization deposits		[4]				[6]
Common stock dividends paid		[4]		[5]		[6]
Investment contract deposits	$ 298,237	[4]	$ 105,019	[5]	$ 117,723	[6]
Investment contract withdrawals	(52,957)	[4]	(54,108)	[5]	(34,677)	[6]
Net cash provided by financing activities	$ 245,280	[4]	$ 50,911	[5]	$ 83,046	[6]
Effects of exchange rate on cash		[4]		[5]		[6]
Increase (decrease) in cash and cash equivalents	$ (551)	[4]	$ (16,162)	[5]	$ (4,420)	[6]
Cash and cash equivalents at the beginning of period	1,482	[7]	17,644	[6]	22,064	[6]
Cash and cash equivalents at the end of the period	931	[8]	1,482	[7]	17,644	[6]
Eliminations [Member]
Cash flow from operating activities:
Net earnings	(35,522)		(34,783)		(29,992)
Earnings from consolidated subsidiaries	$ 35,522		$ 34,783		$ 29,992
Adjustments to reconcile net earnings to cash provided by operations:
Depreciation
Amortization of deferred policy acquisition costs
Interest credited to policy holders
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 taxes
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			$ 211	[9]	$ 725	[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			$ (211)	[9]	$ (725)	[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					$ 11,589	[9]
Proceeds from sale and paydowns of:
Property, plant and equipment
Short term investments
Fixed maturities investments
Equity securities
Preferred stock
Real estate
Mortgage loans					$ (11,589)	[9]
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 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 year ended December 31, 2015

[2] Balances for the year ended December 31, 2014

[3] Balances for the year ended December 31, 2013

[4] Balance for the period ended December 31, 2015

[5] Balance for the period ended December 31, 2014

[6] Balance for the period ended December 31, 2013

[7] Balances as of December 31, 2014

[8] Balances as of December 31, 2015

[9] Eliminate intercompany investments