Equity (Distributions) (Detail) (USD $) In Thousands, except Per Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Distribution per share	$ 0.90	$ 0.35	$ 0
Payment Amount	$ 355,574	$ 137,765	$ 0
First Quarter [Member]
Dividends Payable, Date Declared	Mar. 22, 2012
Dividends Payable, Date to be Paid	Apr. 25, 2012
Dividends Payable, Date of Record	Apr. 11, 2012
Distribution per share	$ 0.21
Payment Amount	82,900
Second Quarter [Member]
Dividends Payable, Date Declared	Jun. 20, 2012
Dividends Payable, Date to be Paid	Jul. 02, 2012
Dividends Payable, Date of Record	Jul. 02, 2012
Distribution per share	$ 0.22
Payment Amount	86,900
Third Quarter [Member]
Dividends Payable, Date Declared	Sep. 19, 2012
Dividends Payable, Date to be Paid	Oct. 01, 2012
Dividends Payable, Date of Record	Oct. 01, 2012
Distribution per share	$ 0.23
Payment Amount	90,900
Fourth Quarter [Member]
Dividends Payable, Date Declared	Dec. 06, 2012
Dividends Payable, Date to be Paid	Dec. 17, 2012
Dividends Payable, Date of Record	Dec. 17, 2012
Distribution per share	$ 0.24
Payment Amount	$ 94,800