Debt Facilities - Convertible Debt (Detail) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended	12 Months Ended				24 Months Ended
	Jun. 30, 2016	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2009	Dec. 31, 2015	Jun. 15, 2016	Jun. 30, 2009
Debt Instrument [Line Items]
Issuance of common stock, convertible securities				$ 150,025
Shares issued in exchange for convertible subordinated notes	380,779
Repayment of debt		$ 447,473	$ 2,277,798	$ 1,462,888
Common shares reserved for issuance, capped call		7,005,645
Adjustments to APIC, convertible debt with conversion feature	$ 141,700
Share price (dollars per share)							$ 372.10
4.75% convertible subordinated notes
Debt Instrument [Line Items]
Interest rate (percent)	4.75%	4.75%
Convertible Subordinated Debt | 4.75% convertible subordinated notes
Debt Instrument [Line Items]
Aggregate principal debt amount issued								$ 373,800
Interest rate (percent)								4.75%
Issuance of common stock, convertible securities	$ 150,100					$ 223,700
Shares issued in exchange for convertible subordinated notes	1,981,662					2,513,798
Repayment of debt	$ 3,600					$ 51,700
Capped call premium, total					$ 49,700
Common shares reserved for issuance, capped call					4,432,638