Subsequent Events - Narrative (Detail) (Merger Agreement [Member], CreXus [Member], USD $) In Millions, except Per Share data, unless otherwise specified	1 Months Ended
	Jan. 30, 2013 Director
Subsequent Event [Line Items]
Acquisition of share price per share	$ 13.00
Percentage of valid tender and purchase number of shares for merger	51.00%
Transaction solicitation period	45 days
Minimum allowable tender offer price increase - per share	$ 0.10
Out-of-pocket expenses reimbursable in case of termination	$ 5
Percentage of outstanding shares ownership before the merger	12.40%
Required outstanding shares holding percentage, short-form merger provision	90.00%
Independent directors	3
Superior Proposal [Member]
Subsequent Event [Line Items]
Required termination notice - days	2 days
Merger termination fee	25
Transaction Solicitation Period [Member]
Subsequent Event [Line Items]
Merger termination fee	$ 15