Antidilution adjustments of convertible note hedges.

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Class of warrant or right exercise price of warrants or rights issued.

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Debt instrument, convertible, maximum threshold percentage.

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Debt instrument issuance costs amortization period.

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Payments for Convertible Note Hedge, Net, Financing Activities

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Expiration, mandatory redemption, or due date, in CCYY-MM-DD format, of the financial instrument issued in exchange for the original debt being converted in a noncash or part noncash transaction.

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Amount of a favorable spread to a debt holder between the amount of debt being converted and the value of the securities received upon conversion. This is an embedded conversion feature of convertible debt issued that is in-the-money at the commitment date.

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The carrying amount of the equity component of convertible debt which may be settled in cash upon conversion.

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

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Remaining amortization period for discount on the liability component of convertible debt which may be settled in cash upon conversion, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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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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Threshold number of specified trading days that common stock price to conversion price of convertible debt instruments must exceed threshold percentage within a specified consecutive trading period to trigger conversion feature.

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Date the debt agreement requires the first payment to be made, in CCYY-MM-DD format.

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

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Description of the frequency of periodic payments (monthly, quarterly, annual).

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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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Date when the debt instrument is scheduled to be fully repaid, in CCYY-MM-DD format.

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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 of current borrowing capacity under the credit facility considering any current restrictions on the amount that could be borrowed (for example, borrowings may be limited by the amount of current assets), but without considering any amounts currently outstanding under the facility.

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The cash outflow to reacquire common stock during the period.

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The cash inflow from additional borrowings, net of cash paid to third parties in connection with debt origination.

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Number of shares that have been repurchased during the period and have not been retired and are not held in treasury. Some state laws may govern the circumstances under which an entity may acquire its own stock and prescribe the accounting treatment therefore. This element is used when state law does not recognize treasury stock.

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Debt - Additional Information (Detail) $ / shares in Units, $ in Thousands, shares in Millions		3 Months Ended	6 Months Ended		12 Months Ended
	Dec. 12, 2016 USD ($) Customer shares	Jun. 30, 2019 USD ($) $ / shares	Jun. 30, 2019 USD ($) $ / shares	Jul. 01, 2018 USD ($)	Dec. 31, 2018 USD ($) shares	Dec. 31, 2016 USD ($) $ / shares	Apr. 27, 2015 USD ($)
Debt Instrument
Repurchase of common stock			$ 247,222	$ 360,795
1.25% Convertible Senior Unsecured Notes Due December 15, 2023
Debt Instrument
Aggregate principal amount	$ 460,000	$ 460,000	$ 460,000		$ 460,000
Debt instrument, interest rate, stated percentage	1.25%
Debt instrument, net proceeds after issuance costs	$ 450,800
Payment for net cost of convertible note hedges net of warrant proceeds	33,000
Repurchase of common stock	$ 50,100
Repurchase of stock, shares \| shares	2.0
Senior notes maturity date	Dec. 15, 2023
Debt instrument, frequency of periodic payment	payable semiannually in arrears on June 15 and December 15 of each year
Debt instrument, date of first required payment	Jun. 15, 2017
Debt instrument, conversion option expiration date	Sep. 15, 2023
Debt instrument conversion price \| $ / shares		$ 31.70	$ 31.70			$ 31.70
Shares that would be issued upon conversion \| shares					14.5
Strike price per share of warrant \| $ / shares		$ 39.78
Debt instrument, convertible, carrying amount of equity component		$ 100,800	$ 100,800
Financing cost		4,800	$ 4,800			$ 7,200
Debt issuance costs, amortization period			7 years
Unamortized discount		$ 72,800	$ 72,800
Debt Instrument, convertible, remaining discount amortization period			4 years 6 months
Value of notes converted			$ 695,200
1.25% Convertible Senior Unsecured Notes Due December 15, 2023 \| Conversion option one
Debt Instrument
Trading days measurement period \| Customer	20
Consecutive trading days measurement period \| Customer	30
Percentage of conversion price	130.00%
1.25% Convertible Senior Unsecured Notes Due December 15, 2023 \| Conversion option two
Debt Instrument
Trading days measurement period \| Customer	5
Consecutive trading days measurement period \| Customer	5
Percentage of closing sale price of common stock and conversion rate product	98.00%
Revolving Credit Facility \| Maximum
Debt Instrument
Credit facility, borrowing capacity							$ 350,000