Cash, Cash Equivalents, and Investments | Cash, Cash Equivalents, and Investments Cash, cash equivalents, and investments consisted of the following (in thousands): September 29, 2019 December 31, 2018 Cash $ 105,620 $ 104,655 Money market instruments 16,081 3,557 Cash and cash equivalents 121,701 108,212 Treasury bills 105,454 198,477 Asset-backed securities 89,576 78,407 Corporate bonds 87,209 137,871 Sovereign bonds 6,300 8,101 Municipal bonds 3,533 4,492 Current investments 292,072 427,348 Treasury bills 256,615 32,760 Corporate bonds 167,998 162,566 Asset-backed securities 56,816 53,631 Sovereign bonds 16,000 6,316 Agency bonds 5,905 5,921 Municipal bonds 1,307 845 Non-current investments 504,641 262,039 $ 918,414 $ 797,599 Treasury bills consist of debt securities issued by the U.S. government; asset-backed securities consist of debt securities collateralized by pools of receivables or loans with credit enhancement; corporate bonds consist of debt securities issued by both domestic and foreign companies; sovereign bonds consist of direct debt issued by foreign governments; municipal bonds consist of debt securities issued by state and local government entities; agency bonds consist of domestic or foreign obligations of government agencies and government sponsored enterprises that have government backing. All securities are denominated in U.S. Dollars. The following table summarizes the Company’s available-for-sale investments as of September 29, 2019 (in thousands): Amortized Gross Gross Fair Value Current: Treasury bills $ 105,254 $ 212 $ (12 ) $ 105,454 Asset-backed securities 89,226 359 (9 ) 89,576 Corporate bonds 86,990 222 (3 ) 87,209 Sovereign bonds 6,286 14 — 6,300 Municipal bonds 3,535 — (2 ) 3,533 Non-current: Treasury bills 255,441 1,253 (79 ) 256,615 Corporate bonds 167,464 584 (50 ) 167,998 Asset-backed securities 56,636 195 (15 ) 56,816 Sovereign bonds 15,969 43 (12 ) 16,000 Agency bonds 5,930 — (25 ) 5,905 Municipal bonds 1,300 7 — 1,307 $ 794,031 $ 2,889 $ (207 ) $ 796,713 The following table summarizes the Company’s gross unrealized losses and fair values for available-for-sale investments in an unrealized loss position as of September 29, 2019 (in thousands): Unrealized Loss Position For: Less than 12 Months 12 Months or Greater Total Fair Value Unrealized Losses Fair Value Unrealized Losses Fair Value Unrealized Losses Treasury bills $ 108,863 $ (91 ) $ — $ — $ 108,863 $ (91 ) Corporate bonds 23,263 (17 ) 20,713 (36 ) 43,976 (53 ) Asset-backed securities 11,149 (15 ) 8,093 (9 ) 19,242 (24 ) Sovereign bonds 11,558 (12 ) — — 11,558 (12 ) Agency bonds 5,905 (25 ) — — 5,905 (25 ) Municipal bonds — — 343 (2 ) 343 (2 ) $ 160,738 $ (160 ) $ 29,149 $ (47 ) $ 189,887 $ (207 ) As of September 29, 2019 , the Company did not recognize any other-than-temporary impairment of these investments. In its evaluation, management considered the type of security, the credit rating of the security, the length of time the security has been in a loss position, the size of the loss position, the Company's intent and ability to hold the security to expected recovery of value, and other meaningful information. The Company does not intend to sell, and is unlikely to be required to sell, any of these available-for-sale investments before their effective maturity or market price recovery. The Company recorded gross realized gains and gross realized losses on the sale of debt securities totaling $361,000 and $67,000 , respectively, during the three-month period ended September 29, 2019 and $283,000 and $17,000 , respectively, during the three-month period ended September 30, 2018 . The Company recorded gross realized gains and gross realized losses on the sale of debt securities totaling $818,000 and $103,000 , respectively, during the nine-month period ended September 29, 2019 and $646,000 and $111,000 , respectively, during the nine-month period ended September 30, 2018 . These gains and losses are included in "Investment income" on the Consolidated Statements of Operations. Prior to the sale of these securities, unrealized gains and losses for these debt securities, net of tax, are recorded in shareholders’ equity as accumulated other comprehensive loss. The following table presents the effective maturity dates of the Company’s available-for-sale investments as of September 29, 2019 (in thousands): <1 year 1-2 Years 2-3 Years 3-4 Years 4-5 Years Total Treasury bills $ 105,454 $ 188,398 $ 68,217 $ — $ — $ 362,069 Corporate bonds 87,209 115,941 47,842 1,348 2,867 255,207 Asset-backed securities 89,576 21,425 26,142 7,633 1,616 146,392 Sovereign bonds 6,300 16,000 — — — 22,300 Agency bonds — — 5,905 — — 5,905 Municipal bonds 3,533 — 1,307 — — 4,840 $ 292,072 $ 341,764 $ 149,413 $ 8,981 $ 4,483 $ 796,713 |