Acquisition of Crexus - Narrative (Detail) (USD $)	6 Months Ended	12 Months Ended
Jun. 30, 2013	Dec. 31, 2014	Dec. 31, 2013
Business Acquisition [Line Items]
Business acquisition agreement date		Jan. 30, 2013
Goodwill	$ 71,400,000us-gaap_Goodwill	$ 94,781,000us-gaap_Goodwill	$ 94,781,000us-gaap_Goodwill
Goodwill adjustment	400,000us-gaap_GoodwillPeriodIncreaseDecrease
Business combination loss recognized	18,900,000
Business acquisition transaction cost			$ 7,300,000

Date when the business acquisition agreement was executed, in CCYY-MM-DD format.

No definition available.

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- Details

Name:	us-gaap_BusinessAcquisitionLineItems
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- Definition

This element represents acquisition-related costs incurred to effect a business combination which costs have been expensed during the period. Such costs include finder's fees; advisory, legal, accounting, valuation, and other professional or consulting fees; general administrative costs, including the costs of maintaining an internal acquisitions department; and may include costs of registering and issuing debt and equity securities.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 805

-SubTopic 10

-Section 25

-Paragraph 23

-URI http://asc.fasb.org/extlink&oid=34752592&loc=d3e1043-128460

+ Details

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- Definition

In a business combination achieved in stages, this element represents the amount of loss recognized by the entity as a result of remeasuring to fair value the equity interest in the acquiree it held before the business combination.

+ References

No definition available.

+ Details

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- Definition

Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 350

-SubTopic 20

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=35741047&loc=d3e13816-109267

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 350

-SubTopic 20

-Section 45

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6388280&loc=d3e13770-109266

+ Details

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- Definition

Amount of increase (decrease) of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

+ References

+ Details

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