Derivative Instruments and Hedging Activities Derivative Instruments and Hedging Activities Gain or Loss Recognized Related to 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
Derivative [Line Items]
Amount of gain related to the effective portion recognized in other comprehensive income (loss)		$ 15,639	$ 0	$ 12,106	$ 0
Amount of loss related to the effective portion subsequently reclassified to earnings (1)	[1]	(628)	(624)	(1,255)	(1,253)
Amount of gain (loss) related to the ineffective portion and amount excluded from effectiveness testing		$ 0	$ 0	$ 0	$ 0

[1] (1) Consists of amounts from previous interest rate hedging programs.