Stockholders' Equity (Prepaid Share Repurchase Forward Contract) - Additional Information (Detail) - Share Repurchase Plan [Member] $ in Thousands	12 Months Ended
Dec. 31, 2017 USD ($) shares
Subsequent Event [Line Items]
Number of outstanding prepaid share repurchase forward contract	2
Deutsche Bank AG, London Branch [Member] \| 3.875% Convertible Senior Notes [Member]
Subsequent Event [Line Items]
Repurchase of common stock under prepaid forward contract \| $	$ 29,923
Repurchase of Common stock, shares \| shares	622,751
Prepaid stock repurchases forward contract settlement period	2019
Societe Generale [Member] \| 4.25% Convertible Senior Notes [Member]
Subsequent Event [Line Items]
Repurchase of common stock under prepaid forward contract \| $	$ 9,400
Repurchase of Common stock, shares \| shares	191,100
Prepaid stock repurchases forward contract settlement period	2022

Adjustments to additional paid in capital stock repurchase forward contract prepaid amount.

No definition available.

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- Definition

Number of outstanding prepaid share repurchase forward contract.

+ References

No definition available.

+ Details

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- Definition

Prepaid stock repurchase forward contract settlement period.

+ References

No definition available.

+ Details

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- Definition

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.

+ 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(28))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.3-04)
-URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187085-122770

Reference 3: 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(29))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=84159872&loc=d3e21463-112644

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- Definition

Detail information of subsequent event by type. User is expected to use existing line items from elsewhere in the taxonomy as the primary line items for this disclosure, which is further associated with dimension and member elements pertaining to a subsequent event.

+ References

No definition available.

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- Details

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- Details

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- Details

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