0.5% Convertible Senior Notes and Capped Call - Schedule of Liability Component of Convertible Debt (Details) - Convertible Debt - Convertible Senior Notes Due 2023 - USD ($) $ in Thousands	Sep. 30, 2018	May 31, 2018	Mar. 31, 2018
Debt Instrument [Line Items]
Principal	$ 500,250		$ 0
Unamortized debt discount	(95,741)		0
Unamortized issuance costs	(8,685)	$ (11,600)	0
Net carrying amount	$ 395,824		$ 0

Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt.

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Amount, after accumulated amortization, of debt discount.

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Amount, after accumulated amortization, of debt issuance costs. Includes, but is not limited to, legal, accounting, underwriting, printing, and registration costs.

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Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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