Equity - Changes in Other Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning Balance	$ 1,340,835	$ 1,412,491
Ending Balance	1,274,384	1,429,994
AOCI Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning Balance	1,065	(1,033)
Ending Balance	1,311	259
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	494	688
Amounts of (income) loss reclassified from accumulated other comprehensive income (loss) to interest expense	$ (248)	$ 604