4. Available-for-Sale Securities and Fair Value Measurements

Available-for-Sale Securities

The classification of available-for-sale securities in the condensed consolidated balance sheets is as follows:

(In thousands)	June 30, 2015		December 31, 2014
Cash and cash equivalents	$	140,146	$	95,090
Short-term marketable securities	79,684		143,698
Marketable securities	—		42,856

Total	$	219,830	$	281,644

The estimated fair value of available-for-sale securities is based on quoted market prices for these or similar investments that were based on prices obtained from a commercial pricing service. Available-for-sale securities are summarized below:

	June 30, 2015
(In thousands)	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Estimated Fair Value
U.S. government securities	$	7,499	$	4	$	—		$	7,503
U.S. government agencies	15,965		2		—			15,967
Corporate notes	46,241		4		(20		)	46,225
Commercial paper	9,989		—		—			9,989
Money market funds	140,146		—		—			140,146

Total	$	219,840	$	10	$	(20	)	$	219,830

	December 31, 2014
(In thousands)	Amortized Cost		Gross Unrealized Gains		Gross Unrealized Losses			Other Than Temporary Impairment Loss			Estimated Fair Value
U.S. government securities	$	30,019	$	24	$	—		$	—		$	30,043
U.S. government agencies	34,756		6		(12		)	—			34,750
Corporate notes	80,880		5		(110		)	—			80,775
Commercial paper	34,469		—		—			—			34,469
Ordinary shares of Theravance Biopharma	10,269		—		—			(3,752		)	6,517
Money market funds	95,090		—		—			—			95,090

Total	$	285,483	$	35	$	(122	)	$	(3,752	)	$	281,644

At June 30, 2015, all of the available-for-sale securities had contractual maturities within one year and the weighted average duration of marketable securities was approximately four months. We do not intend to sell the investments that are in an unrealized loss position, and it is unlikely that we will be required to sell the investments before recovery of their amortized cost basis, which may be maturity. We have determined that the gross unrealized losses on our marketable securities at June 30, 2015 were temporary in nature. All marketable securities with unrealized losses at June 30, 2015 have been in a loss position for less than twelve months.

During the six months ended June 30, 2015, we recognized a gain of $1.2 million from the sale of all of the ordinary shares of Theravance Biopharma that we held at December 31, 2014, which is included in other income (expense), net in the condensed consolidated statement of operations. In addition, we sold other available-for-sale securities totaling $49.4 million, and the related realized gains and losses were not significant during the six months ended June 30, 2015.

Fair Value Measurements

Our available-for-sale securities are measured at fair value on a recurring basis and our debt is carried at the amortized cost basis. The estimated fair values were as follows:

	Estimated Fair Value Measurements at Reporting Date Using:
Types of Instruments	Quoted Price in Active Markets for Identical Assets		Significant Other Observable Inputs		Significant Unobservable Inputs
(In thousands)	Level 1		Level 2		Level 3		Total
Assets at June 30, 2015
U.S. government securities	$	7,503	$	—	$	—	$	7,503
U.S. government agencies	—		15,967		—		15,967
Corporate notes	—		46,225		—		46,225
Commercial paper	—		9,989		—		9,989
Money market funds	140,146		—		—		140,146

Total assets measured at estimated fair value	$	147,649	$	72,181	$	—	$	219,830

Liabilities at June 30, 2015
Convertible subordinated notes due 2023	$	—	$	239,802	$	—	$	239,802
Non-recourse notes due 2029	—		476,113		—		476,113

Total fair value of liabilities	$	—	$	715,915	$	—	$	715,915

	Estimated Fair Value Measurements at Reporting Date Using:
Types of Instruments	Quoted Price in Active Markets for Identical Assets		Significant Other Observable Inputs		Significant Unobservable Inputs
(In thousands)	Level 1		Level 2		Level 3		Total
Assets at December 31, 2014
U.S. government securities	$	30,043	$	—	$	—	$	30,043
U.S. government agencies	—		34,750		—		34,750
Corporate notes	—		80,775		—		80,775
Commercial paper	—		34,469		—		34,469
Ordinary shares of Theravance Biopharma	6,517		—		—		6,517
Money market funds	95,090		—		—		95,090

Total assets measured at estimated fair value	$	131,650	$	149,994	$	—	$	281,644

Liabilities at December 31, 2014
Convertible subordinated notes due 2023	$	—	$	197,095	$	—	$	197,095
Non-recourse notes due 2029	—		456,411		—		456,411

Total fair value of liabilities	$	—	$	653,506	$	—	$	653,506

The fair value of our marketable securities classified within Level 2 were derived from observable inputs that may include benchmark yields, reported trades, broker/dealer quotes, issuer spreads, two-sided markets, benchmark securities, bids, offers and reference data including market research publications.

The fair value of our convertible subordinated notes due 2023 and non-recourse notes due 2029 is based on recent trading prices of the instruments, if applicable, or pricing models that utilize current observable market characteristics for similar types of instruments.