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Short-term Investments | 12 Months Ended
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Dec. 31, 2018
Short Term Investments [Abstract] |
Short-term Investments | (4) Short-term Investments The Company periodically invests a portion of its excess cash in short-term investment instruments. Substantially all of the Company’s short-term investments are in U.S. Treasury securities and all short-term investments have stated maturity dates between three months and one year from the purchase date. All short-term investments are included within “Short-term investments” on the accompanying Consolidated Balance Sheets. The fair value of the Company’s short-term investments is determined based on quoted market prices in active markets for identical securities (Level 1 inputs). In the fourth quarter of 2018, the Company began to redeem certain short-term investments prior to their stated maturity dates. As a result, all short-term investments were reclassified from held-to-maturity to available-for-sale. As of December 31, 2018, all short-term investments are classified as available-for-sale and reported at fair value. The amortized cost and fair value of available-for-sale investments at December 31, 2018 were $466.6 million and $466.2 million, respectively. The gross unrecognized holding losses accumulated in other comprehensive loss were $0.4 million for the year ended December 31, 2018. The gross unrecognized holding gains accumulated in other comprehensive loss were not material for the year-ended December 31, 2018. No other-than-temporary impairments related to these available-for-sale investments have been recognized as of December 31, 2018. As of December 31, 2017, all short-term investments were classified as held-to-maturity and reported at amortized cost. The amortized cost, carrying value, and fair value of held-to-maturity investments at December 31, 2017 were $254.9 million, $254.9 million, and $254.8 million, respectively. The gross unrecognized holding gains and losses were not material for the years ended December 31, 2017 and 2016. No other-than-temporary impairments related to these held-to-maturity investments have been recognized as of December 31, 2017.

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- Definition The entire disclosure for investments in certain debt and equity securities. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 320 -URI http://asc.fasb.org/subtopic&trid=2209399 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 946 -SubTopic 320 -URI http://asc.fasb.org/subtopic&trid=2324412 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -URI http://asc.fasb.org/topic&trid=2196928 Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 940 -SubTopic 320 -URI http://asc.fasb.org/subtopic&trid=2176304 + Details
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