ACCOUNTING CHANGES AND NEW ACCOUNTING PRONOUNCEMENTS (Details)	3 Months Ended
	Sep. 30, 2012 Change In Estimated Residual Values [Member]	Mar. 31, 2012 Change In Estimated Useful Life [Member]
Change In Accounting Estimate [Line Items]
Change in accounting estimate, financial effect	During third quarter 2012, the Company changed the estimated residual values of its entire fleet of owned 737-300 and 737-500 aircraft.  This change was based on an agreement entered into during July 2012, pursuant to which the Company will lease or sublease certain aircraft to Delta Air Lines, Inc. (“Delta”), and the resulting impact this transaction will have on how the Company manages the ultimate retirement of its owned 737-300 and 737-500 aircraft.  See Note 8 for further information on the lease/sublease transaction.  Based on the expected retirement dates and current and expected future market conditions related to its owned 737-300 and 737-500 aircraft, the Company reduced the residual values of these aircraft from approximately ten percent of original cost to approximately two percent of original cost.  As this reduction in residual value is considered a change in estimate, it has been accounted for on a prospective basis, and thus the Company will record additional depreciation expense over the remainder of the useful lives for each aircraft.  The impact of this change on the year ended December 31, 2012 was an increase in depreciation expense of approximately $34 million, excluding the impact of profitsharing and income taxes ($18 million after the impact of profitsharing and taxes, with a $.02 decrease in both basic and diluted net income per share).	During first quarter 2012, the Company changed the estimated retirement dates of several 737-300 and 737-500 aircraft based on revisions in the Company’s fleet plan.  This change, which was accounted for on a prospective basis, resulted in an acceleration of depreciation expense, since the majority of these aircraft had previously been expected to retire in periods beyond 2012, but were subsequently expected to be retired during 2012.  For the year ended December 31, 2012, the impact of this change was an increase in depreciation expense of approximately $12 million, excluding the impact of profitsharing and income taxes ($6 million after the impact of profitsharing and taxes, with a $.01 decrease in both basic and diluted net income per share).