SCHEDULE II VALUATION AND QUALIFYING ACCOUNTS (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Valuation and qualifying accounts
Balance at beginning of period	$ 2,454	$ 1,333	$ 900
(Recovered) charged to costs and expenses	(14)	2,010	775
Deductions		(889)	(342)
Balance at end of period	2,440	2,454	1,333
Allowance for doubtful accounts and other receivables
Valuation and qualifying accounts
Balance at beginning of period	981	704	760
(Recovered) charged to costs and expenses	(60)	1,166	(56)
Deductions		(889)
Balance at end of period	921	981	704
Straight-line rent receivable allowance
Valuation and qualifying accounts
Balance at beginning of period	1,473	629	140
(Recovered) charged to costs and expenses	46	844	831
Deductions			(342)
Balance at end of period	$ 1,519	$ 1,473	$ 629