Derivative and Hedging Instruments Derivative Instruments and Hedging Activities Gain or Loss Recognized Related to Cash Flow Hedges (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Derivative [Line Items]
Losses from interest rate contracts		$ 0	$ (140)	$ 0
Amount of loss related to the effective portion recognized in other comprehensive loss		(6,133)	(47,144)	(10,302)
Amount of loss related to the effective portion subsequently reclassified to earnings (1)	[1]	(6,033)	(3,751)	(2,510)
Amount of loss related to the ineffective portion and amount excluded from effectiveness testing		$ 0	(140)	$ 0
Prior hedge program [Member]
Derivative [Line Items]
Losses from interest rate contracts			$ (200)

[1] During the year ended December 31, 2016, the Company accelerated the reclassification of amounts in other comprehensive loss to earnings as a result of the hedged forecasted transactions becoming probable not to occur. The accelerated amounts were a loss of approximately $0.2 million and are included in the table above.