Real Estate and Accumulated Depreciation (Details 1) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Investment in real estate:
Balance, beginning of year	$ 512,227	$ 372,746	$ 347,157
Acquisitions, improvements and development expenditures	158,175	140,866	25,937
Disposition of properties	(1,015)	(710)	(71)
Other reclassifications	0	(675)	(277)
Balance, end of year	669,387	512,227	372,746
Accumulated depreciation:
Balance, beginning of year	76,164	57,463	38,999
Depreciation for the year	22,472	18,943	18,299
Disposition of properties	(865)	(242)	(21)
Other reclassifications	49	0	186
Balance, end of year	97,820	76,164	57,463
Development in process	50,781	45,278	24,232
Investment in real estate, net	$ 622,348	$ 481,341	$ 339,515