Common stock shares covered under capped call transactions.

No definition available.

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- Definition

Debt instrument conversion price measuring average period.

+ References

No definition available.

+ Details

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- Definition

Maturity date of credit facility if certain other conditions have not been met.

+ References

No definition available.

+ Details

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- Definition

To repay early minimum required amount outstanding with certain other conditions have not been met.

+ References

No definition available.

+ Details

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- Definition

Including the current and noncurrent portions, carrying amount of debt identified as being convertible into another form of financial instrument (typically the entity's common stock) as of the balance sheet date, which originally required full repayment more than twelve months after issuance or greater than the normal operating cycle of the company.

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Balance Type:	credit
Period Type:	instant

- Definition

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.

+ References

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- Definition

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

+ References

No definition available.

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Balance Type:	na
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- Definition

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

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-Section 50
-Paragraph 5
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- Definition

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.

+ References

No definition available.

+ Details

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Period Type:	duration

- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
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Balance Type:	na
Period Type:	duration

- Definition

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

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Balance Type:	debit
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- Definition

Difference between the fair value of payments made and the carrying amount of debt which is extinguished prior to maturity.

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- Definition

The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

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Balance Type:	credit
Period Type:	instant

- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

+ Details

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Balance Type:	credit
Period Type:	instant

- Definition

The fee, expressed as a percentage of the line of credit facility, for available but unused credit capacity under the credit facility.

+ References

No definition available.

+ Details

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Balance Type:	na
Period Type:	duration

- Definition

The cash outflow from the repayment 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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Debt - Additional Information (Detail) - USD ($)			1 Months Ended
Debt - Additional Information (Detail) - USD ($)	Oct. 19, 2018	Oct. 15, 2018	Nov. 30, 2016	Sep. 30, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Convertible notes outstanding				$ 1,200,349,000	$ 1,174,470,000
The 2016 Credit Facility
Debt Instrument [Line Items]
Outstanding amount				$ 0	$ 0
The 2016 Credit Facility \| Revolving Credit Facility
Debt Instrument [Line Items]
Maturity date of convertible debt			Nov. 29, 2018
Maximum borrowing capacity			$ 100,000,000
The 2016 Credit Facility \| Letter of credit subfacility
Debt Instrument [Line Items]
Maximum borrowing capacity			10,000,000
The 2016 Credit Facility \| Swingline loan subfacility
Debt Instrument [Line Items]
Maximum borrowing capacity			$ 15,000,000
Subsequent Event \| 0.75% Senior Subordinated Convertible Notes Due in October 2018
Debt Instrument [Line Items]
Maturity date of convertible debt		Oct. 15, 2018
Debt conversion, principal cash settlement amount		$ 375,000,000
Common stock, shares, issued to converting holders		190,220
Debt instrument, convertible, conversion price, per share		$ 94.15
Debt Instrument, conversion price measuring average period		25 days
Common stock shares covered under capped call transactions \| shares		95,127
Gain (loss) on extinguishment or termination of debt		$ 0
Subsequent Event \| The 2016 Credit Facility
Debt Instrument [Line Items]
Gain (loss) on extinguishment or termination of debt	$ 0
Maximum borrowing capacity	$ 200,000,000
Subsequent Event \| The 2018 Credit Facility
Debt Instrument [Line Items]
Maturity date of convertible debt	Oct. 19, 2021
To repay early, minimum required amount outstanding with certain other conditions have not been met	$ 100,000,000
Maturity date of credit facility, if certain other conditions have not been met	Aug. 01, 2020
Debt issuance costs	$ 1,000,000
Subsequent Event \| The 2018 Credit Facility \| Minimum
Debt Instrument [Line Items]
Percentage of commitment fees payable on undrawn amount	0.15%
Subsequent Event \| The 2018 Credit Facility \| Minimum \| LIBOR Rate
Debt Instrument [Line Items]
Debt instrument interest rate percentage	1.00%
Subsequent Event \| The 2018 Credit Facility \| Minimum \| Base Rate
Debt Instrument [Line Items]
Debt instrument interest rate percentage	0.00%
Subsequent Event \| The 2018 Credit Facility \| Maximum
Debt Instrument [Line Items]
Percentage of commitment fees payable on undrawn amount	0.35%
Subsequent Event \| The 2018 Credit Facility \| Maximum \| LIBOR Rate
Debt Instrument [Line Items]
Debt instrument interest rate percentage	1.95%
Subsequent Event \| The 2018 Credit Facility \| Maximum \| Base Rate
Debt Instrument [Line Items]
Debt instrument interest rate percentage	0.95%