Real Property Acquisitions and Development (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012
Pro forma consolidated results of operations
Revenues	$ 1,328,847	$ 1,083,555
Income from continuing operations attributable to common stockholders	$ (7,081)	$ 36,559
Income from continuing operations attributable to common stockholders per share:
Basic	$ (0.03)	$ 0.18
Diluted	$ (0.03)	$ 0.18