Marketable Securities - Narrative (Q3) (Details)	9 Months Ended
Sep. 30, 2021 USD ($)
Investments, Debt and Equity Securities [Abstract]
Unrealized gain (loss) on marketable securities	$ 0

Amount of unrealized gain (loss) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

No definition available.

Name:	us-gaap_DebtSecuritiesAvailableForSaleUnrealizedGainLoss
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration