Fair Value of Financial Instruments - Unrestricted Marketable Securities (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Fair Value of Financial Instruments
Corporate debt securities, Amortized Cost	$ 83,535	$ 57,910
Corporate debt securities, Gross Unrealized Gains	5	4
Corporate debt securities, Gross Unrealized Losses	(493)	(158)
Corporate debt securities, Fair Value	83,047	57,756
Contractual maturities of the unrestricted marketable securities held
Less Than 1 Year	28,038
1-5 years	55,009
Corporate debt securities, Fair Value	$ 83,047	$ 57,756

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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Amount before tax of unrealized gain in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

+ References

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-Publisher FASB
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Amount before tax of unrealized loss in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

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This item represents the cost of debt and equity securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any.

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Fair value of available-for-sale debt securities maturing in the second fiscal year through the fifth fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

+ References

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Fair value of available-for-sale debt securities maturing in the next fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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