Real Property Acquisitions and Development (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Pro forma consolidated results of operations
Revenues	$ 647,269	$ 531,936
Income from continuing operations attributable to common stockholders	$ (30,479)	$ 23,164
Income from continuing operations attributable to common stockholders per share:
Basic	$ (0.12)	$ 0.12
Diluted	$ (0.12)	$ 0.11