FAIR VALUE MEASUREMENTS

3 Months Ended

Mar. 31, 2017

In determining fair value, there is a three-level hierarchy based on the reliability of the inputs used. Level 1 refers to fair values based on quoted prices in active markets for identical assets or liabilities. Level 2 refers to fair values estimated using significant other observable inputs and Level 3 refers to fair values estimated using significant unobservable inputs.

Fair Value of Financial Instruments on a Recurring Basis

As of March 31, 2017, total cost basis for all marketable securities was $1,529 million. There were no significant differences between the cost basis and fair value of any individual class of marketable securities. Fair values of financial instruments on the consolidated balance sheet (in millions):



March 31, 2017	Level 1		Level 2			Total
Assets
Marketable securities
U.S. government and agency securities	$	416	$	—		$	416
Foreign government bonds	—		38			38
Asset-backed securities	—		194			194
Mortgage-backed securities	—		88			88
Corporate notes and bonds	—		780			780
Municipal securities	—		11			11
Total Marketable securities	416		1,111			1,527
Derivative instruments
Fuel hedge call options	—		10			10
Interest rate swap agreements	—		9			9
Total Assets	416		1,130			1,546

Liabilities
Derivative instruments
Interest rate swap agreements	—		(12		)	(12		)
Total Liabilities	—		(12		)	(12		)



December 31, 2016	Level 1		Level 2			Total
Assets
Marketable securities
U.S. government and agency securities	$	287	$	—		$	287
Foreign government bonds	—		36			36
Asset-backed securities	—		138			138
Mortgage-backed securities	—		89			89
Corporate notes and bonds	—		691			691
Municipal securities	—		11			11
Total Marketable securities	287		965			1,252
Derivative instruments
Fuel hedge call options	—		20			20
Total Assets	287		985			1,272

Liabilities
Derivative instruments
Interest rate swap agreements	—		(5		)	(5		)
Total Liabilities	—		(5		)	(5		)

The Company uses the market and income approach to determine the fair value of marketable securities. U.S. government securities are Level 1 as the fair value is based on quoted prices in active markets. Foreign government bonds, asset-backed securities, mortgage-backed securities, corporate notes and bonds, and municipal securities are Level 2 as the fair value is based on standard valuation models that are calculated based on observable inputs such as quoted interest rates, yield curves, credit ratings of the security and other observable market information.

The Company uses the market approach and the income approach to determine the fair value of derivative instruments. The fair value for fuel hedge call options is determined utilizing an option pricing model based on inputs that are readily available in active markets or can be derived from information available in active markets. In addition, the fair value considers the exposure to credit losses in the event of non-performance by counterparties. Interest rate swap agreements are Level 2 as the fair value of these contracts is determined based on the difference between the fixed interest rate in the agreements and the observable LIBOR-based interest forward rates at period end multiplied by the total notional value.

Activity and Maturities for Marketable Securities

Activity for marketable securities (in millions):



	Three Months Ended March 31,
	2017			2016
Proceeds from sales and maturities	$	285		$	140
Gross realized gains	1			—
Gross realized losses	(1		)	—
Gross unrealized gains	3			10
Gross unrealized losses	(5		)	(2		)

Maturities for marketable securities (in millions):



March 31, 2017	Cost Basis		Fair Value
Due in one year or less	$	236	$	236
Due after one year through five years	1,281		1,278
Due after five years through 10 years	12		13
Due after 10 years	—		—
Total	$	1,529	$	1,527

Unrealized losses from fixed-income securities are primarily attributable to changes in interest rates. Management does not believe any remaining unrealized losses represent other-than-temporary impairments based on its evaluation of available information as of March 31, 2017.

Fair Value of Other Financial Instruments

The Company used the following methods and assumptions to determine the fair value of financial instruments that are not recognized at fair value as described below.

Cash and Cash Equivalents: Carried at amortized cost, which approximates fair value.

Debt: The carrying amount of the Company's variable-rate debt approximates fair value. For fixed-rate debt, the Company uses the income approach to determine the estimated fair value, calculated as the sum of future cash flows discounted at borrowing rates for comparable debt over the weighted life of the outstanding debt. The estimated fair value of the fixed-rate debt is Level 3 as certain inputs used are unobservable.

Fixed-rate debt that is not carried at fair value on the consolidated balance sheet and the estimated fair value of long-term fixed-rate debt is as follows (in millions):



	March 31, 2017		December 31, 2016
Carrying amount	$	1,116	$	1,179
Fair value	1,130		1,199

Assets and Liabilities Measured at Fair Value on Nonrecurring Basis

Certain assets and liabilities are recognized or disclosed at fair value on a nonrecurring basis, including property, plant and equipment, goodwill, and intangible assets. These assets are subject to fair valuation when there is evidence of impairment. No impairment was recognized in the three months ended March 31, 2017.

- Definition

The entire disclosure for the fair value of financial instruments (as defined), including financial assets and financial liabilities (collectively, as defined), and the measurements of those instruments as well as disclosures related to the fair value of non-financial assets and liabilities. Such disclosures about the financial instruments, assets, and liabilities would include: (1) the fair value of the required items together with their carrying amounts (as appropriate); (2) for items for which it is not practicable to estimate fair value, disclosure would include: (a) information pertinent to estimating fair value (including, carrying amount, effective interest rate, and maturity, and (b) the reasons why it is not practicable to estimate fair value; (3) significant concentrations of credit risk including: (a) information about the activity, region, or economic characteristics identifying a concentration, (b) the maximum amount of loss the entity is exposed to based on the gross fair value of the related item, (c) policy for requiring collateral or other security and information as to accessing such collateral or security, and (d) the nature and brief description of such collateral or security; (4) quantitative information about market risks and how such risks are managed; (5) for items measured on both a recurring and nonrecurring basis information regarding the inputs used to develop the fair value measurement; and (6) for items presented in the financial statement for which fair value measurement is elected: (a) information necessary to understand the reasons for the election, (b) discussion of the effect of fair value changes on earnings, (c) a description of [similar groups] items for which the election is made and the relation thereof to the balance sheet, the aggregate carrying value of items included in the balance sheet that are not eligible for the election; (7) all other required (as defined) and desired information.

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