Summary of Aggregate Consideration and Preliminary Fair Value of Assets Acquired and Liabilities Assumed Recognized at Acquisition Date (Detail) (USD $) In Thousands, unless otherwise specified					0 Months Ended
	Sep. 30, 2014	Dec. 31, 2013		Jun. 30, 2013	Apr. 17, 2013 CreXus	Apr. 17, 2013 CreXus	Apr. 17, 2013 CreXus Commercial real estate investments	Apr. 17, 2013 CreXus Accrued interest receivable	Apr. 17, 2013 CreXus Participation sold
Business Acquisition [Line Items]
Cash consideration transferred					$ 876,267
Fair value of equity interest in CreXus held before the business combination					106,521
Business Combination, Consideration Transferred, Including Equity Interest in Acquiree Held Prior to Combination, Total					982,788
Recognized amounts of identifiable assets acquired and liabilities assumed
Cash and cash equivalents						151,843
Recognized amounts of identifiable assets							796,950	3,485
Other assets						5,617
Mortgages payable						(19,376)
Participation sold									(14,352)
Accounts payable and accrued expenses						(12,729)
Total identifiable net assets						911,438
Goodwill	94,781	94,781	[1]	71,400		71,350
Recognized amounts of identifiable assets						$ 982,788

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