Condensed Consolidated Statements of Changes in Shareholders’ Equity - USD ($) $ in Thousands	Total	Common Stock	Common Stock Subscribed, Unissued	Retained Earnings	Accumulated Other Comprehensive Loss	Noncontrolling Interests
Balance at Dec. 31, 2015	$ 688,146	$ 326,482	$ 0	$ 548,780	$ (190,435)	$ 3,319
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	15,097			15,045		52
Other comprehensive income (loss)	7,976				7,735	241
Stock issued	8,015	8,015
Stock purchased	(2,888)	(2,647)				(241)
Advance payments	508		508
Dividends declared	(4,983)			(4,983)
Balance at Mar. 31, 2016	711,871	331,850	508	558,842	(182,700)	3,371
Balance at Dec. 31, 2016	730,889	348,771	0	575,380	(196,600)	3,338
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	17,723			17,681		42
Other comprehensive income (loss)	3,758				3,692	66
Stock issued	8,282	8,282
Stock purchased	(3,984)	(3,629)				(355)
Advance payments	1,020		1,020
Dividends declared	(5,306)			(5,306)
Balance at Mar. 31, 2017	$ 752,382	$ 353,424	$ 1,020	$ 587,755	$ (192,908)	$ 3,091