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, 2013	$ 670,781	$ 317,767	$ 0	$ 489,740	$ (140,363)	$ 3,637
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	40,457			40,365		92
Other comprehensive income	5,699				5,715	$ (16)
Stock issued	9,211	9,211
Stock purchased	(10,592)	(10,306)				$ (286)
Advance payments	860		860
Dividends declared	(9,548)			(9,548)
Balance at Jun. 30, 2014	706,868	316,672	860	520,557	(134,648)	3,427
Balance at Dec. 31, 2014	681,981	317,199	0	513,672	(152,193)	3,303
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	37,639			37,548		91
Other comprehensive income	1,253				1,417	$ (164)
Stock issued	10,105	10,105
Stock purchased	(8,071)	(7,974)				$ (97)
Advance payments	917		917
Dividends declared	(9,616)			(9,616)
Balance at Jun. 30, 2015	$ 714,208	$ 319,330	$ 917	$ 541,604	$ (150,776)	$ 3,133