Acquisition of Crexus - Narrative (Detail) (USD $)	6 Months Ended	9 Months Ended	12 Months Ended
	Jun. 30, 2013	Sep. 30, 2014	Dec. 31, 2013
Business Acquisition [Line Items]
Business acquisition agreement date		Jan. 30, 2013
Goodwill	$ 71,400,000	$ 94,781,000	$ 94,781,000	[1]
Goodwill adjustment	400,000
Business combination loss recognized	18,900,000
Business acquisition transaction cost			$ 7,300,000

[1] Derived from the audited consolidated financial statements at December 31, 2013.