Derivative Instruments - Designated as hedging, Financial Performance (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016	Dec. 31, 2015
Derivative Instruments, Gain (Loss) [Line Items]
Accumulated Other Comprehensive Income (Loss), Cumulative Changes in Net Gain (Loss) from Cash Flow Hedges, Effect Net of Tax	$ 0	$ (5,450)	$ 0	$ (5,450)	$ (2,520)	$ (1,790)
Designated as Hedging Instrument [Member] | Interest Rate Swap [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Accumulated Other Comprehensive Income (Loss), Cumulative Changes in Net Gain (Loss) from Cash Flow Hedges, Effect Net of Tax	0		0		$ (2,520)
Designated as Hedging Instrument [Member] | Interest Rate Swap [Member] | Interest Expense [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	20	(250)	(320)	(470)
Designated as Hedging Instrument [Member] | Interest Rate Swap [Member] | Debt financing and related expenses [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Derivative Instruments, Gain (Loss) Reclassified from Accumulated OCI into Income, Effective Portion, Net	$ (4,680)	$ 0	$ (4,680)	$ 0