Short-term Investments	12 Months Ended
Dec. 31, 2019
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. 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 classified as available-for-sale and reported at fair value 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). The amortized cost and fair value of available-for-sale investments at December 31, 2019 were $108.8 million and $108.9 million, respectively. 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 not material as of December 31, 2019 and 2018. The gross unrecognized holding gains accumulated in other comprehensive loss were not material as of December 31, 2019 and 2018. No other-than-temporary impairments related to these available-for-sale investments have been recognized as of December 31, 2019 and 2018.

Short-term Investments

12 Months Ended

Dec. 31, 2019

(4) Short-term Investments

The Company periodically invests a portion of its excess cash in short-term investment instruments. 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 classified as available-for-sale and reported at fair value 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).

The amortized cost and fair value of available-for-sale investments at December 31, 2019 were $108.8 million and $108.9 million, respectively. 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 not material as of December 31, 2019 and 2018. The gross unrecognized holding gains accumulated in other comprehensive loss were not material as of December 31, 2019 and 2018. No other-than-temporary impairments related to these available-for-sale investments have been recognized as of December 31, 2019 and 2018.