Investments	9 Months Ended
Sep. 30, 2021
Debt Securities, Available-for-sale [Abstract]
Investments	InvestmentsHistorically, we have invested our excess cash primarily in debt instruments of financial institutions, corporations, U.S. government-sponsored agencies and the U.S. Treasury. We generally hold our investments to maturity and do not sell our investments before we have recovered our amortized cost basis. As of September 30, 2021 and December 31, 2020, our cash balance was comprised entirely of cash and cash equivalents (money market funds).

The entire disclosure for investments in certain debt and equity securities.

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

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher SEC
-Name Regulation S-K (SK)
-Number 229
-Section 1403
-Paragraph (b)

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