Derivative Financial Instruments - Schedule of Derivatives, Gain (Loss) on Derivative Activity (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Derivative Instruments, Gain (Loss) [Line Items]
Cash settlements paid			$ (77,526)	$ 9,620
Interest rate swaps | Not designated as hedging instrument
Derivative Instruments, Gain (Loss) [Line Items]
Beginning fair value of interest rate swaps	$ (1,540)	$ (4,047)	(2,080)	(4,759)
Cash settlements paid	698	824	1,386	1,710
Ending fair value of interest rate swaps	(985)	(3,332)	(985)	(3,332)
Interest rate swaps | Not designated as hedging instrument | Interest expense
Derivative Instruments, Gain (Loss) [Line Items]
Total loss on interest rate swaps	$ (143)	$ (109)	$ (291)	$ (283)