Derivatives (Details 1) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 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	(64)	8,251	(2,016)	9,263
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	$ 64	$ (8,251)	$ 2,016	$ (9,263)