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
Stockholders' Equity Attributable to Noncontrolling Interest [Roll Forward]
Net income	7,979			7,946		33
Other comprehensive income	2,437				2,505	(68)
Stock issued	5,843	5,843
Stock purchased	(3,017)	(2,954)				(63)
Advance payments	405		405
Dividends declared	(4,700)			(4,700)
Balance at Mar. 31, 2013	609,163	312,897	405	457,016	(164,309)	3,154
Balance at Dec. 31, 2013	670,781	317,767	0	489,740	(140,363)	3,637
Stockholders' Equity Attributable to Noncontrolling Interest [Roll Forward]
Net income	11,350			11,321		29
Other comprehensive income	155				279	(124)
Stock issued	6,607	6,607
Stock purchased	(5,777)	(5,505)				(272)
Advance payments	443		443
Dividends declared	(4,792)			(4,792)
Balance at Mar. 31, 2014	$ 678,767	$ 318,869	$ 443	$ 496,269	$ (140,084)	$ 3,270