Activity of Hedging Instruments in Accumulated OCI (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Accumulated Other Comprehensive Income (Loss), Net of Tax, Beginning of Period	$ (229,327)
Unrealized gain (loss) on derivative instruments	60	$ (2,782)
Realized losses reclassified into net income (loss)	232	176
Accumulated Other Comprehensive Income (Loss), Net of Tax, End of Period	(213,618)
Accumulated Net Gain (Loss) from Derivative and Nonderivative Instruments Designated as Hedging Instruments [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax, Beginning of Period	(14,337)	(14,062)
Accumulated Other Comprehensive Income (Loss), Net of Tax, End of Period	$ (14,045)	$ (16,668)