Convertible Notes, Net - Summary of Outstanding Convertible Senior Notes (Detail) $ in Thousands	12 Months Ended
Dec. 31, 2017 USD ($)
5.25% Convertible Senior Notes [Member]
Debt Instrument [Line Items]
Convertible Note Issuance	2013-11
Face Value	$ 172,500
Coupon Rate	5.25%
All-in Cost	5.87%
Conversion Rate	36.1380
Maturity	2018-12
4.38% Convertible Senior Notes [Member]
Debt Instrument [Line Items]
Convertible Note Issuance	2017-05
Face Value	$ 402,500
Coupon Rate	4.38%
All-in Cost	4.85%
Conversion Rate	28.0324
Maturity	2022-05

Debt Instrument Interest Rate Stated Percentage Including Amortization Cost

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- Definition

The expiration, mandatory redemption, or due date, month and year (YYYY-MM), of the financial instrument 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 cash payments in the period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=98513485&loc=d3e4332-108586

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-Section 50
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-URI http://asc.fasb.org/extlink&oid=98513485&loc=d3e4304-108586

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- Definition

The month and year (YYYY-MM) the financial instrument was 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 cash payments in the period.

+ References

+ Details

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- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 6
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=84159872&loc=d3e21506-112644

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-Name Accounting Standards Codification
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-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(5))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=64930739&loc=d3e28878-108400

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- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(1))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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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.

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