Fair value measurement

To estimate the fair value of our financial assets and liabilities, we use valuation approaches within a hierarchy that maximizes the use of observable inputs and minimizes the use of unobservable inputs by requiring that observable inputs be used when available. Observable inputs are inputs that market participants would use in pricing an asset or liability based on market data obtained from sources independent of the Company. Unobservable inputs are inputs that reflect the Company’s assumptions about the inputs that market participants would use in pricing an asset or liability and are developed based on the best information available in the circumstances. The fair value hierarchy is divided into three levels based on the source of inputs as follows:



Level 1	—	Valuations based on unadjusted quoted prices in active markets for identical assets or liabilities that the Company has the ability to access
Level 2	—	Valuations for which all significant inputs are observable, either directly or indirectly, other than level 1 inputs
Level 3	—	Valuations based on inputs that are unobservable and significant to the overall fair value measurement

The availability of observable inputs can vary among the various types of financial assets and liabilities. To the extent that the valuation is based on models or inputs that are less observable or unobservable in the market, the determination of fair value requires more judgment. In certain cases, the inputs used for measuring fair value may fall into different levels of the fair value hierarchy. In such cases, for financial statement disclosure purposes, the level in the fair value hierarchy within which the fair value measurement is categorized is based on the lowest level of input used that is significant to the overall fair value measurement.

The fair values of each major class of the Company’s financial assets and liabilities measured at fair value on a recurring basis were as follows (in millions):



	Quoted prices in active markets for identical assets (Level 1)		Significant other observable inputs (Level 2)		Significant unobservable inputs (Level 3)

Fair value measurement as of March 31, 2018, using:							Total
Assets:
Interest-bearing securities:
U.S. Treasury securities	$	5,103	$	—	$	—	$	5,103
Other government-related debt securities:
U.S.	—		129		—		129
Foreign and other	—		1,674		—		1,674
Corporate debt securities:
Financial	—		6,053		—		6,053
Industrial	—		5,565		—		5,565
Other	—		896		—		896
Residential-mortgage-backed securities	—		1,699		—		1,699
Other mortgage- and asset-backed securities	—		1,267		—		1,267
Money market mutual funds	9,234		—		—		9,234
Other short-term interest-bearing securities	—		50		—		50
Equity securities	155		—		—		155
Derivatives:
Foreign currency contracts	—		17		—		17
Cross-currency swap contracts	—		433		—		433
Total assets	$	14,492	$	17,783	$	—	$	32,275

Liabilities:
Derivatives:
Foreign currency contracts	$	—	$	259	$	—	$	259
Cross-currency swap contracts	—		148		—		148
Interest rate swap contracts	—		215		—		215
Contingent consideration obligations in connection with business combinations	—		—		110		110
Total liabilities	$	—	$	622	$	110	$	732



	Quoted prices in active markets for identical assets (Level 1)		Significant other observable inputs (Level 2)		Significant unobservable inputs (Level 3)

Fair value measurement as of December 31, 2017, using:							Total
Assets:
Interest-bearing securities:
U.S. Treasury securities	$	8,242	$	—	$	—	$	8,242
Other government-related debt securities:
U.S.	—		223		—		223
Foreign and other	—		2,422		—		2,422
Corporate debt securities:
Financial	—		10,072		—		10,072
Industrial	—		9,670		—		9,670
Other	—		1,390		—		1,390
Residential-mortgage-backed securities	—		2,168		—		2,168
Other mortgage- and asset-backed securities	—		2,297		—		2,297
Money market mutual funds	3,245		—		—		3,245
Other short-term interest-bearing securities	—		1,440		—		1,440
Equity securities	149		—		—		149
Derivatives:
Foreign currency contracts	—		6		—		6
Cross-currency swap contracts	—		270		—		270
Interest rate swap contracts	—		10		—		10
Total assets	$	11,636	$	29,968	$	—	$	41,604

Liabilities:
Derivatives:
Foreign currency contracts	$	—	$	204	$	—	$	204
Cross-currency swap contracts	—		220		—		220
Interest rate swap contracts	—		61		—		61
Contingent consideration obligations in connection with business combinations	—		—		69		69
Total liabilities	$	—	$	485	$	69	$	554

Interest-bearing and equity securities

The fair values of our U.S. Treasury securities, money market mutual funds and equity securities are based on quoted market prices in active markets with no valuation adjustment.

Most of our other government-related and corporate debt securities are investment grade and have maturity dates of five years or less from the balance sheet date. Our other government-related debt securities portfolio is composed of securities with weighted-average credit ratings of BBB+ or equivalent by Standard & Poor’s Financial Services LLC (S&P), and A- or equivalent by Moody’s Investors Service, Inc. (Moody’s) or Fitch Ratings Inc. (Fitch); and our corporate debt securities portfolio has a weighted-average credit rating of A- or equivalent by Fitch, and BBB + or equivalent by S&P or Moody’s. We estimate the fair values of these securities by taking into consideration valuations obtained from third-party pricing services. The pricing services use industry standard valuation models, including both income- and market-based approaches, for which all significant inputs are observable, either directly or indirectly, to estimate fair value. The inputs include reported trades of and broker-dealer quotes on the same or similar securities; issuer credit spreads; benchmark securities; and other observable inputs.

Our residential-mortgage-, other-mortgage- and asset-backed-securities portfolio is composed entirely of senior tranches, with credit ratings of AAA by S&P, Moody’s or Fitch. We estimate the fair values of these securities by taking into consideration valuations obtained from third-party pricing services. The pricing services use industry standard valuation models, including both income- and market-based approaches, for which all significant inputs are observable, either directly or indirectly, to estimate fair value. The inputs include reported trades of and broker-dealer quotes on the same or similar securities; issuer credit spreads; benchmark securities; prepayment or default projections based on historical data; and other observable inputs.

We value our other short-term interest-bearing securities at amortized cost, which approximates fair value given their near-term maturity dates.

Derivatives

All of our foreign currency forward and option derivative contracts have maturities of three years or less, and all are with counterparties that have minimum credit ratings of A- or equivalent by S&P, Moody’s or Fitch. We estimate the fair values of these contracts by taking into consideration valuations obtained from a third-party valuation service that uses an income-based industry standard valuation model for which all significant inputs are observable, either directly or indirectly. These inputs include foreign currency exchange rates, London Interbank Offered Rate (LIBOR), swap rates and obligor credit default swap rates. In addition, inputs for our foreign currency option contracts include implied volatility measures. These inputs, where applicable, are at commonly quoted intervals. See Note 13, Derivative instruments.

Our cross-currency swap contracts are with counterparties that have minimum credit ratings of A- or equivalent by S&P, Moody’s or Fitch. We estimate the fair values of these contracts by taking into consideration valuations obtained from a third-party valuation service that uses an income-based industry standard valuation model for which all significant inputs are observable either directly or indirectly. These inputs include foreign currency exchange rates, LIBOR, swap rates, obligor credit default swap rates and cross-currency basis swap spreads. See Note 13, Derivative instruments.

Our interest rate swap contracts are with counterparties that have minimum credit ratings of A- or equivalent by S&P, Moody’s or Fitch. We estimate the fair values of these contracts by using an income-based industry standard valuation model for which all significant inputs are observable either directly or indirectly. These inputs include LIBOR, swap rates and obligor credit default swap rates. See Note 13, Derivative instruments.

Contingent consideration obligations

As a result of our business acquisitions, we incurred contingent consideration obligations, as discussed below. The contingent consideration obligations are recorded at their fair values by using probability-adjusted discounted cash flows, and we revalue these obligations each reporting period until the related contingencies have been resolved. The fair value measurements of these obligations are based on significant unobservable inputs related to licensing rights and product candidates acquired in business combinations, and are reviewed quarterly by management in our R&D and commercial sales organizations. These inputs include, as applicable, estimated probabilities and timing of achieving specified regulatory and commercial milestones and estimated annual sales. Significant changes that increase or decrease the probabilities of achieving the related regulatory and commercial events, or that shorten or lengthen the time required to achieve such events, or that increase or decrease estimated annual sales would result in corresponding increases or decreases in the fair values of the obligations, as applicable. Changes in the fair values of contingent consideration obligations are recognized in Other operating expenses in the Condensed Consolidated Statements of Income.

Changes in the carrying amounts of contingent consideration obligations were as follows (in millions):



	Three months ended March 31,
	2018			2017
Beginning balance	$	69		$	179
Addition from K-A acquisition	45			—
Net changes in valuations	(4		)	5
Ending balance	$	110		$	184

As a result of our acquisition of BioVex Group, Inc., in 2011, we are obligated to pay its former shareholders additional consideration contingent upon achieving certain sales-related milestones with regard to IMLYGIC^®(talimogene laherparepvec).

As a result of our acquisition of K-A in 2018, we are obligated to make single-digit-percentage royalty payments to Kirin contingent upon sales of brodalumab. See Note 3, Business combinations.

During the three months ended March 31, 2018 and 2017, there were no transfers of assets or liabilities between fair value measurement levels, and there were no material remeasurements to the fair values of assets and liabilities that are not measured at fair value on a recurring basis.

Summary of the fair values of other financial instruments

Cash equivalents

The fair values of cash equivalents approximate their carrying values due to the short-term nature of such financial instruments.

Borrowings

We estimated the fair values of our borrowings by using Level 2 inputs. As of March 31, 2018 and December 31, 2017, the aggregate fair values of our borrowings were $37.6 billion and $38.6 billion, respectively, and the carrying values were $35.5 billion and $35.3 billion, respectively.