Marketable Securities

6 Months Ended

Jun. 30, 2017

Investments Debt And Equity Securities [Abstract]

3. Marketable Securities

The following tables present a summary of the Company’s marketable securities, which consist solely of available-for-sale securities (in thousands):

	Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Value
June 30, 2017
Corporate bonds	$	146,069	$	18	$	(229	)	$	145,858
Commercial paper		4,993		—		—			4,993
	$	151,062	$	18	$	(229	)	$	150,851

	Amortized Cost		Unrealized Gains		Unrealized Losses			Fair Value
December 31, 2016
Corporate bonds	$	133,424	$	82	$	(298	)	$	133,208
Common equity securities		300		618		—			918
	$	133,724	$	700	$	(298	)	$	134,126

Common equity securities reported as of December 31, 2016 consisted of shares of common stock of Audentes Therapeutics, Inc. (Audentes), which became a publicly traded company in July 2016. The Company obtained these shares in connection with a license granted to Audentes in July 2013. The Company sold all of its shares of Audentes common stock during the first quarter of 2017.

As of June 30, 2017 and December 31, 2016, no available-for-sale securities had remaining maturities greater than three years.

The amortized cost of available-for-sale securities is adjusted for amortization of premiums and accretion of discounts to maturity. As of June 30, 2017 and December 31, 2016, the balance in the Company’s accumulated other comprehensive loss consisted solely of net unrealized gains and losses on available-for-sale securities, net of income tax effects and reclassification adjustments for realized gains and losses. During the three and six months ended June 30, 2017, the Company recognized net unrealized losses on available-for-sale securities of $0.1 million and $0.1 million, respectively, and income tax expense of $0 in other comprehensive loss for the periods. The Company recognized realized gains of $0 and $0.5 million on the sale or maturity of available-for-sale securities during the three and six months ended June 30, 2017, respectively, which were reclassified out of accumulated other comprehensive loss during the periods and are included in investment income in the consolidated statements of operations and comprehensive loss. During the three and six months ended June 30, 2016, the Company recognized net unrealized gains on available-for-sale securities of $0.2 million and $1.2 million, respectively, and income tax expense of $0 in other comprehensive income for the periods. The Company did not recognize any realized gains or losses on the sale or maturity of marketable securities for the three or six months ended June 30, 2016.

The Company did not hold any securities in an unrealized loss position for more than 12 months as of June 30, 2017 or December 31, 2016. The aggregate fair value of securities held by the Company in an unrealized loss position for less than 12 months as of June 30, 2017 and December 31, 2016 was $127.2 million and $102.5 million, respectively. As of June 30, 2017, securities held by the Company which were in an unrealized loss position consisted of 45 investment grade corporate bond positions. The Company has the intent and ability to hold such securities until recovery and has determined that none of its investments were other-than-temporarily impaired as of June 30, 2017 or December 31, 2016.