Condensed Consolidated Statements of Changes in Shareholders’ Equity (USD $) In Thousands, unless otherwise specified	Total	Common Stock	Common Stock Subscribed, Unissued	Retained Earnings	Accumulated Other Comprehensive Loss	Noncontrolling Interests
Balance at Dec. 31, 2012	$ 600,216	$ 310,008	$ 0	$ 453,770	$ (166,814)	$ 3,252
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	58,624			58,470		154
Other comprehensive income	9,992				10,034	(42)
Stock issued	11,419	10,932				487
Stock purchased	(10,235)	(10,105)				(130)
Advance payments	415		415
Dividends	(14,041)			(14,041)
Balance at Sep. 30, 2013	656,390	310,835	415	498,199	(156,780)	3,721
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	70,993			70,829		164
Other comprehensive income	4,735				4,887	(152)
Stock issued	12,067	12,067
Stock purchased	(13,500)	(13,212)				(288)
Advance payments	436		436
Dividends	(14,302)			(14,302)
Balance at Sep. 30, 2014	$ 731,210	$ 316,622	$ 436	$ 546,267	$ (135,476)	$ 3,361