SCHEDULE II VALUATION AND QUALIFYING ACCOUNTS (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Valuation and qualifying accounts
Balance at beginning of period	$ 2,440	$ 2,454	$ 1,333
(Recovered) charged to costs and expenses	(101)	(14)	2,010
Charged to other accounts	0
Deductions	0		(889)
Balance at end of period	2,339	2,440	2,454
Allowance for doubtful accounts and other receivables
Valuation and qualifying accounts
Balance at beginning of period	921	981	704
(Recovered) charged to costs and expenses	(139)	(60)	1,166
Charged to other accounts	0
Deductions	0		(889)
Balance at end of period	782	921	981
Straight-line rent receivable allowance
Valuation and qualifying accounts
Balance at beginning of period	1,519	1,473	629
(Recovered) charged to costs and expenses	38	46	844
Charged to other accounts	0
Deductions	0
Balance at end of period	$ 1,557	$ 1,519	$ 1,473