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Debt - Schedule of Convertible Senior Notes (Detail) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	May 19, 2020	May 15, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Interest Expense	$ 37,590,000	$ 18,897,000	$ 75,182,000	$ 35,363,000
Convertible Debt
Debt Instrument [Line Items]
Aggregate Principal Amount	2,386,717,000		2,386,717,000
Unamortized Debt Discount and Debt Issuance Costs	566,739,000		566,739,000				$ 463,348,000
Fair Value	3,054,058,000		3,054,058,000				2,304,376,000
Contractual Coupon Interest	8,259,000	3,768,000	14,994,000	7,536,000
Accretion of bond discount	23,859,000	8,173,000	45,152,000	16,201,000
Amortization of Debt Issuance Costs	1,340,000	826,000	2,594,000	1,637,000
Interest Expense	33,458,000	12,767,000	62,740,000	25,374,000
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	$ 162,829,000		$ 162,829,000				172,813,000
Fair Value	705,000,000		705,000,000				597,380,000
Contractual Coupon Interest	1,719,000	0	3,438,000	0
Accretion of bond discount	4,922,000	0	9,746,000	0
Amortization of Debt Issuance Costs	120,000	0	238,000	0
Interest Expense	6,761,000	0	13,422,000	0
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	$ 163,214,000		$ 163,214,000			$ 3,300,000	0
Fair Value	659,756,000		659,756,000				0
Contractual Coupon Interest	2,007,000	0	2,007,000	0
Accretion of bond discount	3,148,000	0	3,148,000	0
Amortization of Debt Issuance Costs	168,000	0	168,000	0
Interest Expense	5,323,000	0	5,323,000	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	$ 165,961,000		$ 165,961,000				182,462,000
Fair Value	957,659,000		957,659,000				819,378,000
Contractual Coupon Interest	1,262,000	0	2,510,000	0
Accretion of bond discount	8,095,000	0	15,956,000	0
Amortization of Debt Issuance Costs	278,000	0	545,000	0
Interest Expense	9,635,000	0	19,011,000	0
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	$ 55,402,000		$ 55,402,000				63,575,000
Fair Value	388,113,000		388,113,000				356,464,000
Contractual Coupon Interest	1,402,000	1,402,000	2,804,000	2,804,000
Accretion of bond discount	3,749,000	3,496,000	7,446,000	6,933,000
Amortization of Debt Issuance Costs	366,000	342,000	727,000	678,000
Interest Expense	5,517,000	5,240,000	10,977,000	10,415,000
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	$ 19,333,000		$ 19,333,000				44,498,000
Fair Value	326,688,000		326,688,000				514,312,000
Contractual Coupon Interest	1,803,000	2,300,000	4,103,000	4,600,000
Accretion of bond discount	3,945,000	4,677,000	8,856,000	9,268,000
Amortization of Debt Issuance Costs	408,000	484,000	916,000	959,000
Interest Expense	6,156,000	7,461,000	13,875,000	14,827,000
Convertible Debt \| 2.75% convertible senior notes due 2020
Debt Instrument [Line Items]
Aggregate Principal Amount	$ 9,637,000		$ 9,637,000
Stated Interest Rate	2.75%		2.75%
Unamortized Debt Discount and Debt Issuance Costs	$ 0		$ 0				0
Fair Value	16,842,000		16,842,000				$ 16,842,000
Contractual Coupon Interest	66,000	66,000	132,000	132,000
Accretion of bond discount	0	0	0	0
Amortization of Debt Issuance Costs	0	0	0	0
Interest Expense	$ 66,000	$ 66,000	$ 132,000	$ 132,000