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	40,791			40,680		111
Other comprehensive income	10,694				10,443	251
Stock issued	11,452	11,452
Stock purchased	(5,856)	(5,503)				(353)
Advance payments	511		511
Dividends declared	(9,977)			(9,977)
Balance at Jun. 30, 2016	735,761	332,431	511	579,483	(179,992)	3,328
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	51,124			51,015		109
Other comprehensive income	9,206				9,067	139
Stock issued	11,755	11,755
Stock purchased	(6,972)	(6,613)				(359)
Advance payments	517		517
Dividends declared	(10,624)			(10,624)
Balance at Jun. 30, 2017	$ 785,895	$ 353,913	$ 517	$ 615,771	$ (187,533)	$ 3,227