Derivatives (Details 1) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Location and amount of gains (losses) on derivative instruments and related hedged items
Total	$ 0	$ 0	$ 0	$ 0
Interest expense [Member] | Interest rate swap [Member]
Location and amount of gains (losses) on derivative instruments and related hedged items
Derivative: Interest rate swap	218	2,161	(1,952)	1,012
Interest expense [Member] | Fixed-rate debt [Member]
Location and amount of gains (losses) on derivative instruments and related hedged items
Hedged item: Fixed-rate debt	$ (218)	$ (2,161)	$ 1,952	$ (1,012)