Capital and Financing Transactions - Cash Flow Hedges (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Capital and Financing Transactions [Abstract]
Amount of gain (loss) recognized in other comprehensive loss on derivatives	$ (6,235)	$ 5,992	$ (7,874)	$ 6,481
Amount of loss reclassified from accumulated other comprehensive loss into interest expense	(2,077)	(1,533)	(3,530)	(2,810)
Amount of loss recognized in income on derivatives (ineffective portion, reclassifications of missed forecasted transactions and amounts excluded from effectiveness testing)	$ (197)	$ (386)	$ (197)	$ (386)