Financial Instruments (Tables)

9 Months Ended

Sep. 30, 2016

Investments, Debt and Equity Securities [Abstract]

Marketable Securities

Investments in available-for-sale securities at December 31, 2015 were classified as follows:

	December 31, 2015
Current	$	520,144
Non-current	48,081
Total available-for-sale securities	$	568,225

Available-for-sale Securities

The cost, gross unrealized gains, gross unrealized losses and fair value of the Company's available-for-sale securities were as follows:

	December 31, 2015
	Cost		Gross Unrealized Gains		Gross Unrealized Losses (1)			Fair Value
Debt securities
Corporate bonds	$	336,665	$	55	$	(1,076	)	$	335,644
U.S. government debt (2)	135,226		2		(374		)	134,854
Asset-backed securities	49,759		2		(115		)	49,646
Equity securities	54,371		466		(6,756		)	48,081
Total available-for-sale securities	$	576,021	$	525	$	(8,321	)	$	568,225

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(1) All unrealized loss positions were held at a loss for less than 12 months.

(2) U.S. Treasury obligations, U.S. government agency obligations and U.S. government agency mortgage-backed securities.

Schedule of Realized Gain (Loss)

The proceeds from sales and maturities of available-for-sale securities included in the consolidated statements of cash flows and the gross realized gains and losses included in the consolidated statements of operations are reflected in the table below. The cost of securities sold was determined using the specific identification method.

	Three Months Ended September 30,				Nine Months Ended September 30,
	2016		2015		2016		2015
Proceeds from sales and maturities of securities	$	360,506	$	1,019	$	662,938	$	16,056
Gross realized gains	52,414		—		53,755		3,795
Gross realized losses	13		—		35		—