Capital and Financing Transactions - Cash Flow Hedges (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Capital and Financing Transactions [Abstract]
Amount of gain (loss) recognized in other comprehensive income on derivatives	$ 680	$ (6,341)	$ (4,425)	$ (7,874)
Net loss reclassified from accumulated other comprehensive loss into earnings	1,734	2,114	3,592	3,526
Amount of loss recognized in income on derivatives (ineffective portion, reclassifications of missed forecasted transactions and amounts excluded from effectiveness testing)	$ 1,221	$ 197	$ 1,245	$ 197