Fair values of financial instruments on the consolidated balance sheet (in millions):



March 31, 2012	Level 1		Level 2			Total

Assets
Marketable securities
U.S. government securities	$	347.8	$	—		$	347.8
Foreign government bonds	—		22.9			22.9
Asset-back securities	—		84.4			84.4
Mortgage-back securities	—		114.7			114.7
Corporate notes and bonds	—		508.2			508.2
Municipal securities	—		15.0			15.0
Derivative instruments
Fuel hedge contracts	—		131.5			131.5

Liabilities
Derivative instruments
Interest rate swap agreements	—		(25.6		)	(25.6		)



December 31, 2011	Level 1		Level 2			Total

Assets
Marketable securities
U.S. government securities	$	295.9	$	—		$	295.9
Foreign government bonds	—		25.4			25.4
Asset-back securities	—		58.0			58.0
Mortgage-back securities	—		124.9			124.9
Corporate notes and bonds	—		522.6			522.6
Municipal securities	—		11.9			11.9
Derivative instruments
Fuel hedge contracts	—		116.9			116.9

Liabilities
Derivative instruments
Fuel hedge contracts	—		(10.3		)	(10.3		)
Interest rate swap agreements	—		(28.8		)	(28.8		)

Tabular disclosure of the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments, assets, and liabilities. Such certain disclosures about the financial instruments, assets, and liabilities include: (1) the fair value of the required items together with their carrying amounts (as appropriate) and (2) the methodology and assumptions used in developing such estimates of fair value.

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- Definition

Tabular disclosure of the fair value measurement of assets and liabilities which includes [financial] instruments measured at fair value that are classified in stockholders' equity. Such assets and liabilities may be measured on a recurring or nonrecurring basis. The disclosures which may be required or desired include: (1) for assets and liabilities measured on a recurring basis, disclosure may include: (a) the fair value measurements at the reporting date; (b) the level within the fair value hierarchy in which the fair value measurements in their entirety fall, segregating fair value measurements using quoted prices in active markets for identical assets or liabilities (Level 1), significant other observable inputs (Level 2), and significant unobservable inputs (Level 3); (c) for fair value measurements using significant unobservable inputs (Level 3), a reconciliation of the beginning and ending balances, separately presenting changes during the period attributable to the following: (i) total gains or losses for the period (realized and unrealized), segregating those gains or losses included in earnings (or changes in net assets), and a description of where those gains or losses included in earnings (or changes in net assets) are reported in the statement of income (or activities); (ii) purchases, sales, issuances, and settlements (net); (iii) transfers in and transfers out of Level 3 (for example, transfers due to changes in the observability of significant inputs); (d) the amount of the total gains or losses for the period in subparagraph (c) (i) above included in earnings (or changes in net assets) that are attributable to the change in unrealized gains or losses relating to those assets and liabilities still held at the reporting date and a description of where those unrealized gains or losses are reported in the statement of income (or activities); (e) the valuation technique(s) used to measure fair value and a discussion of changes in valuation techniques, if any, during the period and (2) for assets and liabilities that are measured at fair value on a nonrecurring basis (for example, impaired assets) disclosure may include, in addition to (a) above: (a) the reasons for the fair value measurements recorded; (b) the same as (b) above; (c) for fair value measurements using significant unobservable inputs (Level 3), a description of the inputs and the information used to develop the inputs; and (d) the valuation technique(s) used to measure fair value and a discussion of changes, if any, in the valuation technique(s) used to measure similar assets and/or liabilities in prior periods. Where the quoted price in an active market for the identical liability is not available, the Level 1 input is the quoted price of an identical liability when traded as an asset.

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