Accumulated Other Comprehensive Income (Schedule of Amounts Recognized in Accumulated Other Comprehensive Income (Loss)) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	$ 1,370,656
Ending Balance	1,353,607
Unrealized (Loss) Income On Derivative Instruments [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	2,303	$ (2,100)
Other comprehensive income (loss) before reclassification	834	(5,640)
Amount of loss reclassified from accumulated other comprehensive income to net income (effective portion)	669	1,777
Other comprehensive income (loss) attributable to common stockholders	1,503	(3,863)
Ending Balance	3,806	(5,963)
Accumulated Other Comprehensive Income (Loss) [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	1,823	(2,580)
Other comprehensive income (loss) before reclassification	834	(5,640)
Amount of loss reclassified from accumulated other comprehensive income to net income (effective portion)	669	1,777
Other comprehensive income (loss) attributable to common stockholders	1,503	(3,863)
Ending Balance	$ 3,326	$ (6,443)