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- Definition

Debt Instrument, Convertible, Terms of Conversion Feature, Conversion Amount

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Debt Instrument, Covenant Repurchase Price, Percentage

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Debt Instrument, Redemption Covenant, Percent of Conversion Price, Last Reported Sale Price of Common Stock

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- Definition

Adjustment to additional paid in capital resulting from the recognition of convertible debt instruments as two separate components - a debt component and an equity component. This bifurcation may result in a basis difference associated with the liability component that represents a temporary difference for purposes of applying accounting for income taxes. The initial recognition of deferred taxes for the tax effect of that temporary difference is as an adjustment to additional paid in capital.

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Amount of noncash expense included in interest expense to amortize debt discount and premium associated with the related debt instruments. Excludes amortization of financing costs. Alternate captions include noncash interest expense.

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Amount of amortization expense attributable to debt issuance costs.

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Exercise price per share or per unit of warrants or rights outstanding.

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The number of shares issued in exchange for the original debt being converted in a noncash (or part noncash) transaction. "Part noncash" refers to that portion of the transaction not resulting in cash receipts or payments in the period.

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The price per share of the conversion feature embedded in the debt instrument.

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Ratio applied to the conversion of debt instrument into equity with equity shares divided by debt principal amount.

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Threshold period of specified consecutive trading days within which common stock price to conversion price of convertible debt instrument must exceed threshold percentage for specified number of trading days to trigger conversion feature.

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Minimum percentage of common stock price to conversion price of convertible debt instruments to determine eligibility of conversion.

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Face (par) amount of debt instrument at time of issuance.

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Effective interest rate for the funds borrowed under the debt agreement considering interest compounding and original issue discount or premium.

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Contractual interest rate for funds borrowed, under the debt agreement.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Percentage price of original principal amount of debt at which debt can be redeemed by the issuer.

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The amount of the liability for the conversion option reclassified to stockholders' equity when the embedded option no longer required separation from the host instrument.

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Represents the portion of interest incurred in the period on debt arrangements that was charged against earnings, excluding amortization of debt discount (premium) and financing costs.

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The cash inflow from the issuance of a long-term debt instrument which can be exchanged for a specified amount of another security, typically the entity's common stock, at the option of the issuer or the holder.

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The cash inflow from issuance of rights to purchase common shares at predetermined price (usually issued together with corporate debt).

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Debt 0.75% Senior convertible notes (Details)	1 Months Ended		3 Months Ended		12 Months Ended
Debt 0.75% Senior convertible notes (Details)	Nov. 30, 2018 USD ($) d $ / shares shares	Jun. 30, 2017 USD ($) $ / shares	Mar. 31, 2019 USD ($) d	Mar. 31, 2018 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)
Debt Instrument [Line Items]
Non-cash interest expense			$ 12,200,000	$ 3,700,000
Senior Notes \| Senior convertible notes due 2022
Debt Instrument [Line Items]
Interest rate on convertible notes		0.75%
Aggregate principal amount		$ 400,000,000.0	400,000,000.0		$ 400,000,000.0
Proceeds from convertible debt		$ 389,000,000
Initial conversion price of convertible notes (in dollars per share) \| $ / shares		$ 99.09
Contractual coupon interest rate			700,000	800,000
Non-cash interest expense			3,500,000	3,300,000
Amortization of debt issuance costs			$ 400,000	$ 400,000
Effective interest rate			5.14%
Conversion price in event of fundamental change			100.00%
Conversion multiple			$ 1,000
Conversion percentage based on last reported sale price			140.00%
Debt instrument, redemption price, percentage			100.00%
Senior Notes \| Senior convertible notes due 2023
Debt Instrument [Line Items]
Interest rate on convertible notes	0.75%
Aggregate principal amount	$ 850,000,000		$ 850,000,000.0		850,000,000.0
Proceeds from convertible debt	$ 836,600,000
Initial conversion price of convertible notes (in dollars per share) \| $ / shares	$ 164.29
Contractual coupon interest rate			1,600,000
Non-cash interest expense			7,800,000
Amortization of debt issuance costs			$ 500,000
Effective interest rate			5.63%
Conversion price in event of fundamental change			100.00%
Conversion multiple			$ 1,000
Threshold consecutive trading days \| d	60
Conversion percentage based on last reported sale price			130.00%
Debt instrument, redemption price, percentage			100.00%
Debt instrument, convertible, conversion ratio	0.0060869	0.0100918
Warrants sold to counterparties \| shares	5,200,000
Proceeds from issuance of warrants	$ 183,800,000
Strike price of warrant \| $ / shares	$ 198.3840
Senior Notes \| Additional Paid-In Capital \| Senior convertible notes due 2022
Debt Instrument [Line Items]
Amount reclassified to stockholders' equity						$ 72,600,000
Senior Notes \| Additional Paid-In Capital \| Senior convertible notes due 2023
Debt Instrument [Line Items]
Amount reclassified to stockholders' equity					$ 174,400,000
Senior Notes \| Term of at least 20 trading days during a period of 30 consecutive trading days \| Minimum \| Senior convertible notes due 2022
Debt Instrument [Line Items]
Threshold consecutive trading days \| d			20
Threshold percentage of stock price trigger			130.00%
Senior Notes \| Term of at least 20 trading days during a period of 30 consecutive trading days \| Minimum \| Senior convertible notes due 2023
Debt Instrument [Line Items]
Threshold consecutive trading days \| d			20
Threshold percentage of stock price trigger			130.00%
Senior Notes \| Term of at least 20 trading days during a period of 30 consecutive trading days \| Maximum \| Senior convertible notes due 2022
Debt Instrument [Line Items]
Threshold consecutive trading days \| d			30
Senior Notes \| Term of at least 20 trading days during a period of 30 consecutive trading days \| Maximum \| Senior convertible notes due 2023
Debt Instrument [Line Items]
Threshold consecutive trading days \| d			30
Senior Notes \| Term of five business day period after any five consecutive trading day period \| Senior convertible notes due 2022
Debt Instrument [Line Items]
Threshold consecutive trading days \| d			5
Senior Notes \| Term of five business day period after any five consecutive trading day period \| Senior convertible notes due 2023
Debt Instrument [Line Items]
Threshold consecutive trading days \| d			5
Senior Notes \| Term of five business day period after any five consecutive trading day period \| Maximum \| Senior convertible notes due 2022
Debt Instrument [Line Items]
Threshold consecutive trading days \| d			5
Threshold percentage of stock price trigger			98.00%
Senior Notes \| Term of five business day period after any five consecutive trading day period \| Maximum \| Senior convertible notes due 2023
Debt Instrument [Line Items]
Threshold consecutive trading days \| d			5
Threshold percentage of stock price trigger			98.00%
Designated as Hedging Instrument \| Senior Notes \| Senior convertible notes due 2023
Debt Instrument [Line Items]
Convertible note hedge, number of shares \| shares	5,173,865
Cost of convertible note hedge recognized in additional paid-in capital	$ 218,900,000