SUPPLEMENTAL CONDENSED CONSOLIDATING FINANCIAL INFORMATION BS (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2013	Mar. 31, 2013	Sep. 30, 2012	Mar. 31, 2012
Condensed Financial Statements, Captions [Line Items]
Cash and cash equivalents	$ 313,521	$ 215,623	$ 348,349	$ 261,550
Accounts Receivable, Net, Current	240,876	262,781
Inventories	158,622	153,969
Assets held for sale	26,719	8,290
Prepaid expenses and other current assets	30,950	35,095
Total current assets	770,688	675,758
Intercompany investment	0	0
Investment in unconsolidated affiliates	272,345	272,123
Intercompany notes receivable	0	0
Total property and equipment, at cost	2,552,805	2,414,647
Less - Accumulated depreciation and amortization	(518,142)	(493,575)
Property, Plant and Equipment, Net	2,034,663	1,921,072
Goodwill	29,804	28,897
Other assets	58,492	52,842
Total assets	3,165,992	2,950,692
Accounts payable	70,157	69,821
Accrued Liabilities, Current	169,751	147,681
Current deferred taxes	2,394	0
Short-term borrowings and current maturities of long-term debt	6,989	22,323
Total current liabilities	249,291	239,825
Long-term debt, less current maturities	824,094	764,946
Intercompany notes payable	0	0
Accrued pension liabilities	127,296	126,647
Other liabilities and deferred credits	49,529	57,196
Deferred taxes	155,303	151,121
Common stock	372	367
Additional paid-in capital	752,614	731,883
Retained earnings	1,214,157	1,094,803
Accumulated other comprehensive income (loss)	(188,476)	(199,683)
Treasury shares	(26,304)	(26,304)
Stockholders' equity	1,752,363	1,601,066
Noncontrolling interests	8,116	9,891
Total stockholders' investment	1,760,479	1,610,957
Total liabilities and stockholders' investment	3,165,992	2,950,692
Parent Company [Member]
Condensed Financial Statements, Captions [Line Items]
Cash and cash equivalents	3,982	31,853	134,682	76,609
Accounts Receivable, Net, Current	9,631	18,498
Inventories	0	0
Assets held for sale	0	0
Prepaid expenses and other current assets	2,899	16,071
Total current assets	16,512	66,422
Intercompany investment	1,278,799	1,163,935
Investment in unconsolidated affiliates	0	0
Intercompany notes receivable	1,361,139	1,401,680
Total property and equipment, at cost	43,456	32,249
Less - Accumulated depreciation and amortization	(12,038)	(10,680)
Property, Plant and Equipment, Net	31,418	21,569
Goodwill	0	0
Other assets	220,258	40,877
Total assets	2,908,126	2,694,483
Accounts payable	4,066	4,049
Accrued Liabilities, Current	51,636	29,534
Current deferred taxes	(6,000)	(4,184)
Short-term borrowings and current maturities of long-term debt	6,919	21,875
Total current liabilities	56,621	51,274
Long-term debt, less current maturities	824,094	764,946
Intercompany notes payable	0	0
Accrued pension liabilities	0	0
Other liabilities and deferred credits	9,203	10,761
Deferred taxes	134,639	128,153
Common stock	372	367
Additional paid-in capital	752,614	731,883
Retained earnings	1,214,157	1,094,803
Accumulated other comprehensive income (loss)	(58,867)	(62,892)
Treasury shares	(26,304)	(26,304)
Stockholders' equity	1,881,972	1,737,857
Noncontrolling interests	1,597	1,492
Total stockholders' investment	1,883,569	1,739,349
Total liabilities and stockholders' investment	2,908,126	2,694,483
Guarantor Subsidiaries [Member]
Condensed Financial Statements, Captions [Line Items]
Cash and cash equivalents	4,368	5,370	3,529	3,155
Accounts Receivable, Net, Current	85,951	80,615
Inventories	51,925	51,970
Assets held for sale	19,867	1,268
Prepaid expenses and other current assets	6,331	12,415
Total current assets	168,442	151,638
Intercompany investment	111,435	111,435
Investment in unconsolidated affiliates	150	150
Intercompany notes receivable	0	0
Total property and equipment, at cost	1,297,901	1,219,438
Less - Accumulated depreciation and amortization	(206,507)	(205,746)
Property, Plant and Equipment, Net	1,091,394	1,013,692
Goodwill	4,755	4,756
Other assets	1,219	1,341
Total assets	1,377,395	1,283,012
Accounts payable	50,257	44,017
Accrued Liabilities, Current	24,977	22,404
Current deferred taxes	(542)	115
Short-term borrowings and current maturities of long-term debt	0	0
Total current liabilities	74,692	66,536
Long-term debt, less current maturities	0	0
Intercompany notes payable	510,861	463,184
Accrued pension liabilities	0	0
Other liabilities and deferred credits	8,083	8,530
Deferred taxes	8,743	8,328
Common stock	4,996	4,996
Additional paid-in capital	9,291	9,291
Retained earnings	760,729	722,147
Accumulated other comprehensive income (loss)	0	0
Treasury shares	0	0
Stockholders' equity	775,016	736,434
Noncontrolling interests	0	0
Total stockholders' investment	775,016	736,434
Total liabilities and stockholders' investment	1,377,395	1,283,012
Non-Guarantor Subsidiaries [Member]
Condensed Financial Statements, Captions [Line Items]
Cash and cash equivalents	305,171	178,400	210,138	181,786
Accounts Receivable, Net, Current	221,222	246,612
Inventories	106,697	101,999
Assets held for sale	6,852	7,022
Prepaid expenses and other current assets	21,721	23,263
Total current assets	661,663	557,296
Intercompany investment	0	0
Investment in unconsolidated affiliates	272,195	271,973
Intercompany notes receivable	0	0
Total property and equipment, at cost	1,211,448	1,162,960
Less - Accumulated depreciation and amortization	(299,597)	(277,149)
Property, Plant and Equipment, Net	911,851	885,811
Goodwill	25,049	24,141
Other assets	39,964	149,544
Total assets	1,910,722	1,888,765
Accounts payable	86,996	101,021
Accrued Liabilities, Current	96,608	115,112
Current deferred taxes	8,936	4,069
Short-term borrowings and current maturities of long-term debt	70	448
Total current liabilities	192,610	220,650
Long-term debt, less current maturities	0	0
Intercompany notes payable	1,054,227	963,687
Accrued pension liabilities	127,296	126,647
Other liabilities and deferred credits	32,501	178,525
Deferred taxes	11,921	14,640
Common stock	22,876	22,876
Additional paid-in capital	270,905	270,905
Retained earnings	193,928	62,602
Accumulated other comprehensive income (loss)	(2,061)	19,834
Treasury shares	0	0
Stockholders' equity	485,648	376,217
Noncontrolling interests	6,519	8,399
Total stockholders' investment	492,167	384,616
Total liabilities and stockholders' investment	1,910,722	1,888,765
Consolidations, Eliminations [Member]
Condensed Financial Statements, Captions [Line Items]
Cash and cash equivalents	0	0	0	0
Accounts Receivable, Net, Current	(75,928)	(82,944)
Inventories	0	0
Assets held for sale	0	0
Prepaid expenses and other current assets	(1)	(16,654)
Total current assets	(75,929)	(99,598)
Intercompany investment	(1,390,234)	(1,275,370)
Investment in unconsolidated affiliates	0	0
Intercompany notes receivable	(1,361,139)	(1,401,680)
Total property and equipment, at cost	0	0
Less - Accumulated depreciation and amortization	0	0
Property, Plant and Equipment, Net	0	0
Goodwill	0	0
Other assets	(202,949)	(138,920)
Total assets	(3,030,251)	(2,915,568)
Accounts payable	(71,162)	(79,266)
Accrued Liabilities, Current	(3,470)	(19,369)
Current deferred taxes	0	0
Short-term borrowings and current maturities of long-term debt	0	0
Total current liabilities	(74,632)	(98,635)
Long-term debt, less current maturities	0	0
Intercompany notes payable	(1,565,088)	(1,426,871)
Accrued pension liabilities	0	0
Other liabilities and deferred credits	(258)	(140,620)
Deferred taxes	0	0
Common stock	(27,872)	(27,872)
Additional paid-in capital	(280,196)	(280,196)
Retained earnings	(954,657)	(784,749)
Accumulated other comprehensive income (loss)	(127,548)	(156,625)
Treasury shares	0	0
Stockholders' equity	(1,390,273)	(1,249,442)
Noncontrolling interests	0	0
Total stockholders' investment	(1,390,273)	(1,249,442)
Total liabilities and stockholders' investment	(3,030,251)	(2,915,568)
Land and Building [Member]
Condensed Financial Statements, Captions [Line Items]
Total property and equipment, at cost	111,406	108,593
Land and Building [Member] | Parent Company [Member]
Condensed Financial Statements, Captions [Line Items]
Total property and equipment, at cost	982	939
Land and Building [Member] | Guarantor Subsidiaries [Member]
Condensed Financial Statements, Captions [Line Items]
Total property and equipment, at cost	49,411	48,907
Land and Building [Member] | Non-Guarantor Subsidiaries [Member]
Condensed Financial Statements, Captions [Line Items]
Total property and equipment, at cost	61,013	58,747
Land and Building [Member] | Consolidations, Eliminations [Member]
Condensed Financial Statements, Captions [Line Items]
Total property and equipment, at cost	0	0
Aircraft And Equipment [Member]
Condensed Financial Statements, Captions [Line Items]
Total property and equipment, at cost	2,441,399	2,306,054
Aircraft And Equipment [Member] | Parent Company [Member]
Condensed Financial Statements, Captions [Line Items]
Total property and equipment, at cost	42,474	31,310
Aircraft And Equipment [Member] | Guarantor Subsidiaries [Member]
Condensed Financial Statements, Captions [Line Items]
Total property and equipment, at cost	1,248,490	1,170,531
Aircraft And Equipment [Member] | Non-Guarantor Subsidiaries [Member]
Condensed Financial Statements, Captions [Line Items]
Total property and equipment, at cost	1,150,435	1,104,213
Aircraft And Equipment [Member] | Consolidations, Eliminations [Member]
Condensed Financial Statements, Captions [Line Items]
Total property and equipment, at cost	$ 0	$ 0