Stockholders' Equity of the REIT - Equity Securities Distributions Paid or Payable Per Unit (Parenthetical) (Detail)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Class of Stock [Line Items]
Conversion basis of common stock	0.4464	0.4464	0.4464