Redeemable Convertible Preferred Stock and Redeemable Convertible A-1 Common Stock - Narrative (Details)	1 Months Ended			3 Months Ended		12 Months Ended
	Dec. 31, 2020 shares	Aug. 31, 2019 USD ($) $ / shares shares	Jun. 30, 2019 USD ($) $ / shares shares	Apr. 30, 2021 USD ($) $ / shares shares	Apr. 30, 2019 USD ($) $ / shares shares	Apr. 30, 2021 USD ($) vote $ / shares shares	Apr. 30, 2020 USD ($) shares	Apr. 30, 2019 USD ($) $ / shares shares	Apr. 30, 2018 shares
Temporary Equity [Line Items]
Shares issued, issuance cost | $						$ 7,179,000	$ 0	$ 0
Dividend rate						6.00%
Dividends, declared | $						$ 0	$ 0	$ 0
Redeemable Convertible Preferred Stock, Excluding Series A Preferred Stock
Temporary Equity [Line Items]
Conversion of stock, converted (in shares) | shares	33,628,776
Conversion ratio	1
Series A*
Temporary Equity [Line Items]
Conversion of stock, converted (in shares) | shares	3,499,992
Conversion ratio	1
Shares outstanding (in shares) | shares							3,499,992
Initial conversion price (in dollars per share)				$ 1.998	$ 1.998	$ 1.998		$ 1.998
Liquidation preference, price per share (in dollars per share)				$ 1.998		$ 1.998
Voting rights, votes per share | vote						50
Redeemable Convertible Preferred Stock
Temporary Equity [Line Items]
Carrying value reclassified into stockholders' equity | $				$ 399,800,000		$ 399,753,000
Shares outstanding (in shares) | shares				0	34,192,000	0	37,128,768	34,192,000	31,582,000
Redeemable Convertible A-1 Common Stock
Temporary Equity [Line Items]
Conversion of stock, converted (in shares) | shares	6,666,665
Conversion ratio	1					1
Carrying value reclassified into stockholders' equity | $				$ 18,800,000		$ 18,800,000
Shares outstanding (in shares) | shares				0	6,667,000	0	6,666,665	6,667,000	6,667,000
Liquidation preference, price per share (in dollars per share)				$ 2.82		$ 2.82
Series G
Temporary Equity [Line Items]
Shares outstanding (in shares) | shares							3,893,701
Sale of stock, number of shares issued (in shares) | shares			1,283,325		2,610,376
Sale of stock, shares issued, price per share (in dollars per share)			$ 19.8252		$ 19.8252			$ 19.8252
Proceeds from issuance of stock, net of issuance costs | $			$ 25,400,000		$ 51,500,000	$ 0	$ 25,333,000	$ 51,567,000
Shares issued, issuance cost | $			$ 100,000		$ 300,000		$ 34,000	$ 257,000
Initial conversion price (in dollars per share)				19.8252	$ 19.8252	$ 19.8252		$ 19.8252
Liquidation preference, price per share (in dollars per share)				19.8252		19.8252
Liquidation preference, after initial distribution, price per share threshold (in dollars per share)				29.7378		$ 29.7378
Series H
Temporary Equity [Line Items]
Shares outstanding (in shares) | shares							1,653,928
Sale of stock, number of shares issued (in shares) | shares		1,653,928
Sale of stock, shares issued, price per share (in dollars per share)		$ 30.2310
Proceeds from issuance of stock, net of issuance costs | $		$ 49,800,000				$ 0	$ 49,836,000	$ 0
Shares issued, issuance cost | $		$ 200,000					$ 164,000
Initial conversion price (in dollars per share)				30.231	30.231	$ 30.231		$ 30.231
Liquidation preference, price per share (in dollars per share)				30.231		30.231
Liquidation preference, after initial distribution, price per share threshold (in dollars per share)				$ 45.3468		$ 45.3468
Class B Common Stock
Temporary Equity [Line Items]
Terms of conversion, per share offering price as a multiple of outstanding shares, proceeds (not less than) | $				$ 50,000,000.0		$ 50,000,000.0
Terms of conversion, gross cash proceeds (at least) | $				30,000,000.0		30,000,000.0
Class A Common Stock
Temporary Equity [Line Items]
Terms of conversion, gross cash proceeds (at least) | $				$ 75,000,000.0		$ 75,000,000.0
Terms of conversion, share price (not less than) (in dollars per share)				$ 8.4426		$ 8.4426
Series B*
Temporary Equity [Line Items]
Shares outstanding (in shares) | shares							4,559,999
Initial conversion price (in dollars per share)				1.998	1.998	1.998		1.998
Liquidation preference, price per share (in dollars per share)				1.998		1.998
Series B-1A*
Temporary Equity [Line Items]
Shares outstanding (in shares) | shares							2,430,635
Initial conversion price (in dollars per share)				6.522	6.522	6.522		6.522
Liquidation preference, price per share (in dollars per share)				6.522		6.522
Series B-1B*
Temporary Equity [Line Items]
Shares outstanding (in shares) | shares							92,769
Initial conversion price (in dollars per share)				13.038	13.038	13.038		13.038
Liquidation preference, price per share (in dollars per share)				13.038		13.038
Series C*
Temporary Equity [Line Items]
Shares outstanding (in shares) | shares							2,779,738
Initial conversion price (in dollars per share)				6.84	6.84	6.84		6.84
Liquidation preference, price per share (in dollars per share)				6.84		6.84
Series D
Temporary Equity [Line Items]
Shares outstanding (in shares) | shares							12,278,422
Initial conversion price (in dollars per share)				8.442	8.4426	8.442		8.4426
Liquidation preference, price per share (in dollars per share)				8.4426		8.4426
Liquidation preference, after initial distribution, price per share threshold (in dollars per share)				12.6642		12.6642
Series E
Temporary Equity [Line Items]
Shares outstanding (in shares) | shares							540,003
Initial conversion price (in dollars per share)				21.858	21.8574	21.858		21.8574
Liquidation preference, price per share (in dollars per share)				21.8574		21.8574
Series F
Temporary Equity [Line Items]
Shares outstanding (in shares) | shares							5,399,581
Initial conversion price (in dollars per share)				19.608	$ 19.6068	19.608		$ 19.6068
Liquidation preference, price per share (in dollars per share)				19.6068		19.6068
Liquidation preference, after initial distribution, price per share threshold (in dollars per share)				29.4102		29.4102
Common Stock
Temporary Equity [Line Items]
Minimum share price to avoid conversion adjustment (in dollars per share)				$ 29.4102		$ 29.4102
Series E or Ratchet Preferred
Temporary Equity [Line Items]
Conversion price, adjustment criteria, percent (less than)				1.00%		1.00%