Convertible Senior Notes, Net - Convertible Senior Notes (Details) $ / shares in Units, shares in Millions	1 Months Ended		3 Months Ended		9 Months Ended
	Jun. 30, 2020 USD ($) shares	Sep. 30, 2019 USD ($) shares	Oct. 31, 2020 USD ($) $ / shares shares	Oct. 31, 2019 USD ($)	Oct. 31, 2020 USD ($) day $ / shares shares	Oct. 31, 2019 USD ($)
Debt Instrument [Line Items]
Loss on early extinguishment of debt			$ 89,000	$ 14,572,000	$ 2,263,000	$ 14,572,000
Convertible Senior Notes Due 2023
Debt Instrument [Line Items]
Limitation on sale of common stock due to sale price threshold (in days) | day					80
Convertible Senior Notes Due 2025
Debt Instrument [Line Items]
Redemption price percentage					130.00%
Convertible Senior Notes Due 2026
Debt Instrument [Line Items]
Redemption price percentage					130.00%
Senior Notes | Convertible Senior Notes Due 2023
Debt Instrument [Line Items]
Fixed interest rate			0.25%		0.25%
Net proceeds from notes					$ 335,000,000.0
Debt repurchased, total consideration		$ 224,400,000
Debt repurchase, total consideration	$ 260,500,000	604,800,000
Consideration allocated to debt component	61,800,000	197,700,000
Consideration allocated to equity component	$ 198,700,000	$ 407,100,000
Effective interest rate	4.90%	4.00%	5.68%		5.68%
Face amount of debt instrument	$ 59,600,000	$ 183,100,000
Loss on early extinguishment of debt				14,600,000	$ 2,200,000	14,600,000
Issuance costs			$ 10,000,000.0	$ 3,800,000	10,000,000.0	$ 3,800,000
Senior notes	69,900,000
Debt repurchase, cash portion	$ 200,000
Write off of deferred debt issuance cost					1,000,000.0
Aggregate principal amount			$ 40,246,000		$ 40,246,000
Conversion price (in dollars per share) | $ / shares			$ 48.36		$ 48.36
Limitation on sale of common stock (in days) | day					20
Limitation on sale of common stock due to sale price threshold (in days) | day					30
Threshold percentage of stock price trigger					130.00%
Limit within threshold of consecutive trading days | day					20
Percentage of closing sale price in excess of convertible notes					98.00%
Repayments of debt			$ 300,000		$ 300,000
Original debt amount			10,400,000		$ 10,400,000
Redemption price percentage					100.00%
Issuance costs attributable to liability component			$ 7,700,000		$ 7,700,000
Initial conversion rate of common stock					0.0206795
Period after consecutive trading days | day					5
Senior Notes | Convertible Senior Notes Due 2025
Debt Instrument [Line Items]
Fixed interest rate			0.125%		0.125%
Effective interest rate			4.10%		4.10%
Issuance costs			$ 19,300,000		$ 19,300,000
Aggregate principal amount			$ 1,060,000,000		$ 1,060,000,000
Conversion price (in dollars per share) | $ / shares			$ 188.71		$ 188.71
Limitation on sale of common stock due to sale price threshold (in days) | day					30
Limit within threshold of consecutive trading days | day					20
Percentage of closing sale price in excess of convertible notes					98.00%
Redemption price percentage					100.00%
Redemption face amount			$ 0		$ 0
Issuance costs attributable to liability component			$ 15,300,000		$ 15,300,000
Initial conversion rate of common stock					0.0052991
Period after consecutive trading days | day					5
Sales price as a percentage of conversion price					130.00%
Proceeds from issuance of debt					$ 1,040,700,000
Senior Notes | Convertible Senior Notes Due 2026
Debt Instrument [Line Items]
Fixed interest rate			0.375%		0.375%
Effective interest rate			5.75%		5.75%
Issuance costs			$ 15,200,000		$ 15,200,000
Aggregate principal amount			$ 1,150,000,000		$ 1,150,000,000
Conversion price (in dollars per share) | $ / shares			$ 238.60		$ 238.60
Limitation on sale of common stock due to sale price threshold (in days) | day					30
Limit within threshold of consecutive trading days | day					20
Percentage of closing sale price in excess of convertible notes					98.00%
Redemption price percentage					100.00%
Redemption face amount			$ 0		$ 0
Issuance costs attributable to liability component			11,000,000.0		$ 11,000,000.0
Initial conversion rate of common stock					0.0041912
Period after consecutive trading days | day					5
Sales price as a percentage of conversion price					130.00%
Proceeds from issuance of debt					$ 1,134,800,000
Additional Paid-in Capital | Senior Notes | Convertible Senior Notes Due 2023
Debt Instrument [Line Items]
Issuance costs attributable to equity component			$ 2,300,000		$ 2,300,000
Class A Common Stock | Senior Notes | Convertible Senior Notes Due 2023
Debt Instrument [Line Items]
Shares of class a common stock transferred (in shares) | shares	1.4	3.0
Shares issued during the period | shares			0.2		0.2