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Debt - Schedule of Convertible Senior Notes (Detail) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	May 19, 2020	May 15, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Interest Expense	$ 39,470,000	$ 26,502,000	$ 114,652,000	$ 61,865,000
Convertible Debt
Debt Instrument [Line Items]
Aggregate Principal Amount	2,384,664,000		2,384,664,000
Unamortized Debt Discount and Debt Issuance Costs	539,070,000		539,070,000				$ 463,348,000
Fair Value	4,829,067,000		4,829,067,000				2,304,376,000
Contractual Coupon Interest	9,652,000	4,464,000	24,646,000	12,000,000
Accretion of bond discount	26,252,000	11,143,000	71,404,000	27,288,000
Amortization of Debt Issuance Costs	1,416,000	926,000	4,010,000	2,563,000
Interest Expense	37,320,000	16,533,000	100,060,000	41,851,000
Convertible Debt \| 1.375% convertible senior notes due 2026
Debt Instrument [Line Items]
Aggregate Principal Amount	$ 500,000,000		$ 500,000,000
Stated Interest Rate	1.375%		1.375%
Effective Interest Rate	8.10%		8.10%
Unamortized Debt Discount and Debt Issuance Costs	$ 157,684,000		$ 157,684,000				172,813,000
Fair Value	1,190,750,000		1,190,750,000				597,380,000
Contractual Coupon Interest	1,719,000	420,000	5,157,000	420,000
Accretion of bond discount	5,022,000	1,142,000	14,768,000	1,142,000
Amortization of Debt Issuance Costs	123,000	28,000	361,000	28,000
Interest Expense	6,864,000	1,590,000	20,286,000	1,590,000
Convertible Debt \| 2.75% convertible senior notes due 2025
Debt Instrument [Line Items]
Aggregate Principal Amount	$ 565,000,000		$ 565,000,000		$ 65,000,000.0	$ 500,000,000.0
Stated Interest Rate	2.75%		2.75%		2.75%	2.75%
Effective Interest Rate	10.32%		10.32%
Unamortized Debt Discount and Debt Issuance Costs	$ 156,677,000		$ 156,677,000			$ 3,300,000	0
Fair Value	978,863,000		978,863,000				0
Contractual Coupon Interest	3,884,000	0	5,891,000	0
Accretion of bond discount	6,205,000	0	9,353,000	0
Amortization of Debt Issuance Costs	331,000	0	499,000	0
Interest Expense	10,420,000	0	15,743,000	0
Convertible Debt \| 0.75% convertible senior notes due 2024
Debt Instrument [Line Items]
Aggregate Principal Amount	$ 673,000,000		$ 673,000,000
Stated Interest Rate	0.75%		0.75%
Effective Interest Rate	7.68%		7.68%
Unamortized Debt Discount and Debt Issuance Costs	$ 157,427,000		$ 157,427,000				182,462,000
Fair Value	1,597,480,000		1,597,480,000				819,378,000
Contractual Coupon Interest	1,262,000	275,000	3,772,000	275,000
Accretion of bond discount	8,251,000	1,681,000	24,207,000	1,681,000
Amortization of Debt Issuance Costs	283,000	57,000	828,000	57,000
Interest Expense	9,796,000	2,013,000	28,807,000	2,013,000
Convertible Debt \| 1.50% convertible senior notes due 2023
Debt Instrument [Line Items]
Aggregate Principal Amount	$ 373,750,000		$ 373,750,000
Stated Interest Rate	1.50%		1.50%
Effective Interest Rate	6.99%		6.99%
Unamortized Debt Discount and Debt Issuance Costs	$ 51,215,000		$ 51,215,000				63,575,000
Fair Value	535,771,000		535,771,000				356,464,000
Contractual Coupon Interest	1,402,000	1,402,000	4,206,000	4,206,000
Accretion of bond discount	3,814,000	3,557,000	11,260,000	10,441,000
Amortization of Debt Issuance Costs	373,000	348,000	1,100,000	1,026,000
Interest Expense	5,589,000	5,307,000	16,566,000	15,673,000
Convertible Debt \| 2.00% convertible senior notes due 2021
Debt Instrument [Line Items]
Aggregate Principal Amount	$ 265,330,000		$ 265,330,000
Stated Interest Rate	2.00%		2.00%
Effective Interest Rate	7.43%		7.43%
Unamortized Debt Discount and Debt Issuance Costs	$ 16,067,000		$ 16,067,000				44,498,000
Fair Value	512,949,000		512,949,000				514,312,000
Contractual Coupon Interest	1,326,000	2,300,000	5,429,000	6,900,000
Accretion of bond discount	2,960,000	4,763,000	11,816,000	14,024,000
Amortization of Debt Issuance Costs	306,000	493,000	1,222,000	1,452,000
Interest Expense	4,592,000	7,556,000	18,467,000	22,376,000
Convertible Debt \| 2.75% convertible senior notes due 2020
Debt Instrument [Line Items]
Aggregate Principal Amount	$ 7,584,000		$ 7,584,000
Stated Interest Rate	2.75%		2.75%
Unamortized Debt Discount and Debt Issuance Costs	$ 0		$ 0				0
Fair Value	13,254,000		13,254,000				$ 16,842,000
Contractual Coupon Interest	59,000	67,000	191,000	199,000
Accretion of bond discount	0	0	0	0
Amortization of Debt Issuance Costs	0	0	0	0
Interest Expense	$ 59,000	$ 67,000	$ 191,000	$ 199,000