Earnings Per Share - Computation of Earnings Per Common Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Earnings Per Share [Abstract]
Net income	$ 4,186	$ 5,732	$ 10,340	$ 11,207
Less: Net income attributable to noncontrolling interest	(954)	(936)	(1,939)	(1,880)
Net income attributable to common stockholders	3,232	4,796	8,401	9,327
Less: Allocation to participating securities	(70)	(78)	(140)	(157)
Net income available to common stockholders	$ 3,162	$ 4,718	$ 8,261	$ 9,170
Basic weighted-average common shares	31,552	31,404	31,551	31,410
Dilutive potential common shares	74	83	66	41
Diluted weighted-average common shares	31,626	31,487	31,617	31,451
Basic and diluted earnings per common share	$ 0.10	$ 0.15	$ 0.26	$ 0.29