Convertible Senior Notes - Summary of Debt (Details) - Convertible Senior Notes	1 Months Ended
	Aug. 31, 2019 USD ($) $ / shares	Jun. 30, 2018 USD ($) $ / shares	Jun. 30, 2020 USD ($) $ / shares	Dec. 31, 2019 USD ($)
Convertible Senior Note due 2023, 0.5%
Debt Instrument [Line Items]
Original Principal (including over-allotment)		$ 230,000,000	$ 84,759,000	$ 84,759,000
Coupon Interest Rate		0.50%
Effective Interest Rate		7.00%
Conversion Rate		0.0225572
Initial Conversion Price | $ / shares		$ 44.33	$ 44.33
Principal		$ 230,000,000	$ 84,759,000	84,759,000
Less: debt discount and issuance costs, net of amortization			(14,414,000)	(16,605,000)
Net carrying amount			70,345,000	68,154,000
Equity, net of issuance costs			46,474,000	46,474,000
Convertible Senior Note due 2024, 0.50%
Debt Instrument [Line Items]
Original Principal (including over-allotment)	$ 400,000,000		400,000,000	400,000,000
Coupon Interest Rate	0.50%
Effective Interest Rate	4.96%
Conversion Rate	0.0052809
Initial Conversion Price | $ / shares	$ 189.36
Principal	$ 400,000,000		400,000,000	400,000,000
Less: debt discount and issuance costs, net of amortization			(65,521,000)	(72,669,000)
Net carrying amount			334,479,000	327,331,000
Equity, net of issuance costs			69,749,000	69,749,000
Convertible Senior Note due 2026, 1.0%
Debt Instrument [Line Items]
Original Principal (including over-allotment)	$ 400,000,000.0		400,000,000	400,000,000
Coupon Interest Rate	1.00%
Effective Interest Rate	5.41%
Conversion Rate	0.0052809
Initial Conversion Price | $ / shares	$ 189.36
Principal	$ 400,000,000.0		400,000,000	400,000,000
Less: debt discount and issuance costs, net of amortization			(90,789,000)	(97,010,000)
Net carrying amount			309,211,000	302,990,000
Equity, net of issuance costs			$ 93,380,000	$ 93,380,000