Dividends Declared and Paid on Shares of Common Stock and Noncontrolling Common Units (Detail) (USD $)	3 Months Ended
	Mar. 31, 2013
Dividend Declared [Line Items]
Dividend Period	First Quarter 2013
Amount per Share/Unit	$ 0.21
Dividends Period Covered	January 1, 2013 to March 31, 2013
Dividend Paid Date	Mar. 29, 2013