Summary of Significant Accounting Policies (Q3) (Tables)

9 Months Ended

12 Months Ended

Sep. 30, 2021

Dec. 31, 2020

Accounting Policies [Abstract]

Schedule of Cash and Cash Equivalents

The following table summarizes the period ending cash and cash equivalents from the Company's Condensed Consolidated Balance Sheets and the total cash, cash equivalents, and restricted cash as presented on the Condensed Consolidated Statements of Cash Flows (in thousands):

	Nine Months Ended September 30,
	2021		2020
Cash and cash equivalents	$	243,448	$	10,219
Customer funds		19,288		22,654
Restricted cash (1)		2,596		3,276
Total cash, cash equivalents, and restricted cash	$	265,332	$	36,149

(1) Restricted cash consists of collateral for letters of credit required for leased office space. At September 30, 2021 restricted cash is included in other assets in the Condensed Consolidated Balance Sheets. At December 31, 2020 restricted cash is included in other current assets in the Condensed Consolidated Balance Sheets. The short-term or long-term classification is determined in accordance with the expiration of the underlying letters of credit.

Schedule of Restricted Cash and Cash Equivalents

The following table summarizes the period ending cash and cash equivalents from the Company's Condensed Consolidated Balance Sheets and the total cash, cash equivalents, and restricted cash as presented on the Condensed Consolidated Statements of Cash Flows (in thousands):

	Nine Months Ended September 30,
	2021		2020
Cash and cash equivalents	$	243,448	$	10,219
Customer funds		19,288		22,654
Restricted cash (1)		2,596		3,276
Total cash, cash equivalents, and restricted cash	$	265,332	$	36,149

(1) Restricted cash consists of collateral for letters of credit required for leased office space. At September 30, 2021 restricted cash is included in other assets in the Condensed Consolidated Balance Sheets. At December 31, 2020 restricted cash is included in other current assets in the Condensed Consolidated Balance Sheets. The short-term or long-term classification is determined in accordance with the expiration of the underlying letters of credit.

Schedule of Change in Previously Reported Line Items in the Statements of Cash Flows

The following table presents the effect of the change in presentation to the previously reported line items for the nine months ended September 30, 2020:

	Nine Months Ended September 30, 2020
	As Previously Reported		Adjustment		Revised
Cash flows from financing activities:
Change in customer funds payable	$	—	$	1,528	$	1,528
Net cash provided by financing activities		14,306		1,528		15,834
Net increase in cash, cash equivalents, and restricted cash		8,759		1,528		10,287
Cash, cash equivalents, and restricted cash, beginning of period		4,736		21,126		25,862
Cash, cash equivalents, and restricted cash, end of period	$	13,495	$	22,654	$	36,149

The following tables present the effect of the change in presentation to the previously reported line items in the Statements of Cash Flows for each period indicated:

	Year Ended December 31, 2020								Year Ended December 31, 2019						Year Ended December 31, 2018
	As Previously								As Previously						As Previously
	Reported		Adjustment			Revised			Reported		Adjustment		Revised		Reported			Adjustment		Revised
Cash flows from financing activities:
Change in customer funds payable	$	—	$	(202	)	$	(202	)	$	—	$	3,505	$	3,505	$	—		$	2,854	$	2,854
Net cash provided by financing activities		15,156		(202	)		14,954			19,268		3,505		22,773		(1,143	)		2,854		1,711
Net increase in cash, cash equivalents, and restricted cash		13,183		(202	)		12,981			1,341		3,505		4,846		(31,646	)		2,854		(28,792	)
Cash, cash equivalents, and restricted cash, beginning of period		4,736		21,126			25,862			3,395		17,621		21,016		35,041			14,767		49,808
Cash, cash equivalents, and restricted cash, end of period	$	17,919	$	20,924		$	38,843		$	4,736	$	21,126	$	25,862	$	3,395		$	17,621	$	21,016