Investments (Narrative) (Details)	9 Months Ended
Sep. 30, 2021
Minimum [Member]
Schedule of Available-for-sale Securities [Line Items]
Treasury Bills, term	1 month
Maximum [Member]
Schedule of Available-for-sale Securities [Line Items]
Treasury Bills, term	5 months

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

No definition available.

Name:	us-gaap_ScheduleOfAvailableForSaleSecuritiesLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration