Senior Notes - Summary of Fixed-Rate Senior Notes (Parenthetical) (Detail)	12 Months Ended
Dec. 31, 2014
Mortgage Loans On Real Estate [Abstract]
Redemption of notes	The Company may redeem the senior convertible notes any time on or after November 20, 2015, in whole or in part, for cash equal to 100% of the principal amount of the notes plus accrued and unpaid interest through, but excluding, the redemption date. The holders of the senior convertible notes may require the Company to repurchase its notes in whole or in part on specified dates, the first of which is November 15, 2015, upon the fulfillment of certain conditions.

Description of the payment terms of the debt instrument (for example, whether periodic payments include principal and frequency of payments) and discussion about any contingencies associated with the payment.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 22

-Article 5

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 470

-Section 50

-Paragraph 3

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=6479336&loc=d3e64711-112823

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 210.5-02.22(a)(3))

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

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