Convertible Debt - Narrative (Details)							1 Months Ended
	Aug. 19, 2019 USD ($) day $ / shares	Aug. 14, 2019 $ / shares	Nov. 19, 2018 USD ($) day $ / shares	Nov. 14, 2018 $ / shares	Sep. 15, 2017 USD ($) day $ / shares	Sep. 11, 2017 institution $ / shares	Nov. 30, 2018 USD ($)	Apr. 08, 2020 USD ($) $ / shares	Mar. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)
Debt Instrument [Line Items]
Number of initial purchasers | institution						2
2.50% Accreting Convertible Senior Notes due 2025 | Subsequent Event
Debt Instrument [Line Items]
Debt, aggregate principal								$ 535,000,000.0
Interest rate, stated percentage								2.50%
Conversion price (in usd per share) | $ / shares								$ 72.50
Convertible Debt | 0.375% 2017 Senior Notes due 2022
Debt Instrument [Line Items]
Debt, aggregate principal					$ 431,250,000				$ 431,250,000	$ 431,250,000
Interest rate, stated percentage					0.375%
Proceeds from sale of Notes, net of discounts and offering expenses					$ 420,400,000
Premiums paid for capped call confirmations					44,200,000
Equity component of Notes					$ 95,800,000
Debt, fair value									332,500,000
Initial conversion rate					0.00961
Conversion price (in usd per share) | $ / shares					$ 104.06
Number of trading days (whether or not consecutive) | day					20
Number of trading days (consecutive) | day					30
Percentage of conversion stock price					130.00%
During number of business day period					5 days
Consecutive trading day period (after any)					10 days
Principal amount of Notes					$ 1,000
Measurement period, percentage (less than)					98.00%
Minimum trading days immediately preceding date notice of redemption provided | day					1
Trading days immediately preceding date notice of redemption provided | day					5
Redemption price, percentage of principal amount to be redeemed					100.00%
Default percentage of aggregate principal amount of notes outstanding (not less than)					25.00%
Convertible Debt | 0.375% 2017 Senior Notes due 2022 | Class A common stock
Debt Instrument [Line Items]
Cap price, per share (in usd per share) | $ / shares						$ 154.16
Premium over last reported sale price, percentage						100.00%
Convertible Debt | 0.375% 2017 Senior Notes due 2022 | Over-Allotment Option
Debt Instrument [Line Items]
Over-allotment option included in issuance of notes					$ 56,250,000
Effective interest rate					6.00%
Convertible Debt | 1.125% 2018 Senior Notes Due 2024
Debt Instrument [Line Items]
Debt, aggregate principal			$ 500,000,000.0				$ 575,000,000.0		575,000,000	575,000,000
Interest rate, stated percentage							1.125%
Over-allotment option included in issuance of notes			$ 75,000,000.0				$ 75,000,000.0
Proceeds from sale of Notes, net of discounts and offering expenses							562,000,000.0
Premiums paid for capped call confirmations							$ 93,400,000
Effective interest rate							8.10%
Equity component of Notes							$ 181,500,000
Debt, fair value									401,800,000
Initial conversion rate			0.008591
Number of trading days (whether or not consecutive) | day			20
Number of trading days (consecutive) | day			30
Percentage of conversion stock price			130.00%
During number of business day period			5 days
Consecutive trading day period (after any)			10 days
Principal amount of Notes			$ 1,000
Measurement period, percentage (less than)			98.00%
Minimum trading days immediately preceding date notice of redemption provided | day			1
Trading days immediately preceding date notice of redemption provided | day			5
Redemption price, percentage of principal amount to be redeemed			100.00%
Default percentage of aggregate principal amount of notes outstanding (not less than)			25.00%
Convertible Debt | 1.125% 2018 Senior Notes Due 2024 | Class A common stock
Debt Instrument [Line Items]
Interest rate, stated percentage			1.125%
Conversion price (in usd per share) | $ / shares			$ 116.40
Cap price, per share (in usd per share) | $ / shares			$ 219.63	$ 219.63
Premium over last reported sale price, percentage				150.00%
Convertible Debt | 1.00% 2019 Senior Notes Due 2026
Debt Instrument [Line Items]
Debt, aggregate principal	$ 948,750,000								948,750,000	$ 948,750,000
Interest rate, stated percentage	1.00%
Over-allotment option included in issuance of notes	$ 123,750,000
Proceeds from sale of Notes, net of discounts and offering expenses	935,100,000
Premiums paid for capped call confirmations	$ 145,700,000
Effective interest rate	6.40%
Equity component of Notes	$ 280,300,000
Debt, fair value									$ 538,400,000
Initial conversion rate	0.0067349
Number of trading days (consecutive) | day	30
Percentage of conversion stock price	130.00%
During number of business day period	5 days
Consecutive trading day period (after any)	10 days
Principal amount of Notes	$ 1,000
Measurement period, percentage (less than)	98.00%
Redemption price, percentage of principal amount to be redeemed	100.00%
Default percentage of aggregate principal amount of notes outstanding (not less than)	25.00%
Convertible Debt | 1.00% 2019 Senior Notes Due 2026 | Class A common stock
Debt Instrument [Line Items]
Interest rate, stated percentage	1.00%
Conversion price (in usd per share) | $ / shares	$ 148.48
Number of trading days (whether or not consecutive) | day	20
Number of trading days (consecutive) | day	30
Cap price, per share (in usd per share) | $ / shares	$ 280.15	$ 280.15
Premium over last reported sale price, percentage		150.00%