Fair Value Measurements - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Fair Value Disclosures [Abstract]
Net unrealized gain on derivative designated as cash flow hedge	$ 1,800
Loss expected to be reclassified into interest expense within the next 12 months	3,600
Net unrealized gain on derivative not designated as cash flow hedge	$ 1,348	$ 0	$ 0