Derivatives and Hedging Activities Accumulated Other Comprehensive Income Related to Derivatives (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011	Mar. 31, 2012	Mar. 31, 2011
Derivative [Line Items]
Accumulated other comprehensive income on cash flow hedges, balance at beginning of year			$ (3,106)	$ (1,371)	$ (3,128)	$ (1,935)
Net change in unrealized gain/ (loss) on cash flow hedges	(113)	(1,305)	(135)	(1,869)
Accumulated other comprehensive income on cash flow hedges, balance at end of period	$ (3,241)	$ (3,240)	$ (3,241)	$ (3,240)	$ (3,128)	$ (1,935)