Equity - Changes in Other Comprehensive Income (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning Balance	$ 1,340,835	$ 1,412,491
Ending Balance	1,397,001	1,359,495
AOCI Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning Balance	1,065	(1,033)
Ending Balance	652	510
Accumulated Net Gain (Loss) from Cash Flow Hedges Including Portion Attributable to Noncontrolling Interest [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Other comprehensive income before reclassifications	600	581
Amounts of (income) loss reclassified from accumulated other comprehensive income (loss) to interest expense	$ (1,013)	$ 962