Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance			$ (3,552)
Net current period other comprehensive income	$ 569	$ 705	1,725	$ 9,073
Ending balance	(1,827)		(1,827)
Tax Expense from Amount Recognized in Other Comprehensive Income Related to Derivatives	0	0	0	0
Interest Expense	61,831	62,391	187,810	189,333
Terminated Interest Rate Contract [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Interest Rate, Designated Derivatives, Deferred Gain or Loss Expected to be Amortized In Next Twelve Months			1,361
Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges Amortization [Member] | Interest Rate Contract | Reclassification out of Accumulated Other Comprehensive Income
Accumulated Other Comprehensive Income [Roll Forward]
Interest Expense	569	705	1,725	9,074
Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member] | Interest Rate Contract
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	0	0	0	(690)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	569	705	1,725	9,763
Accumulated Other Comprehensive Income [Roll Forward]
Beginning balance	(2,396)	(4,845)	(3,552)	(13,213)
Net current period other comprehensive income	569	705	1,725	9,073
Ending balance	(1,827)	(4,140)	(1,827)	(4,140)
Tax Expense from Amount Recognized in Other Comprehensive Income Related to Derivatives	0	0	0	0
Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member] | Interest Rate Contract | Reclassification out of Accumulated Other Comprehensive Income
Accumulated Other Comprehensive Income (Loss) [Line Items]
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	569	705	1,725	9,763
Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges, Net Settlements | Interest Rate Contract | Reclassification out of Accumulated Other Comprehensive Income
Accumulated Other Comprehensive Income [Roll Forward]
Tax Expense from Amount Reclassified from Accumulated Other Comprehensive Income into Income	0	0	0	0
Interest Expense	$ 0	$ 0	$ 0	$ 689