Capital and Financing Transactions - Cash Flow Hedges (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Capital and Financing Transactions [Abstract]
Amount of gain (loss) recognized in other comprehensive income (loss) on derivatives	$ 1,448	$ (3,171)	$ (6,235)	$ 3,359
Amount of gain reclassified from accumulated other comprehensive income (loss) into interest expense	1,956	1,393	5,488	4,203
Other comprehensive income (loss)	3,404	(1,778)	(747)	7,562
Amount of gain (loss) recognized in income on derivatives (ineffective portion, reclassifications of missed forecasted transactions and amounts excluded from effectiveness testing)	$ 41	$ (67)	$ (156)	$ (454)