Derivative Financial Instruments - Changes in Fair Value of Derivative Contracts (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Net loss (gain) recognized in other comprehensive income (loss)	$ (3,493)	$ 1,086	$ (5,667)	$ 3,944
Interest rate swap agreements
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Gain reclassified from other comprehensive income (loss) to earnings	(48)	(71)	(95)	(163)
Accumulated Net Gain (Loss) from Cash Flow Hedges Including Portion Attributable to Noncontrolling Interest
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	5,692	2,909	3,548	5,853
Loss (gain) recognized in other comprehensive income (loss)	3,460	(982)	5,590	(3,622)
Amounts reclassified from other comprehensive income (loss) to earnings	42	(85)	103	(297)
Net loss (gain) recognized in other comprehensive income (loss)	3,502	(1,067)	5,693	(3,919)
Ending balance	$ 9,146	$ 1,771	$ 9,146	$ 1,771