Fair Value Measurement - Amount of Gains and Losses from Changes in Fair Value Included in Earnings (Detail) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2016	Mar. 31, 2015
Fair Value Inputs Assets Quantitative Information [Line Items]
Change in fair value	$ 804	$ 561
Construction [Member]
Fair Value Inputs Assets Quantitative Information [Line Items]
Change in fair value	803	561
Total change in fair value	$ 803	$ 561

For each line item in the statement of financial position, the amounts of gains and losses from fair value changes included in earnings.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 825
-SubTopic 10
-Section 50
-Paragraph 30
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=6957238&loc=d3e14172-108612

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration