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, 2010	$ 558,807	$ 232,400	$ 0	$ 423,602	$ (102,343)	$ 5,148
Stockholders' Equity Attributable to Noncontrolling Interest [Roll Forward]
Net income	11,645			11,528		117
Other comprehensive income	4,170				4,071	99
Stock issued	4,402	4,402
Stock purchased	(1,804)	(1,789)				(15)
Advance payments	741		741
Dividends declared	(3,528)			(3,528)
Balance at Mar. 31, 2011	574,433	235,013	741	431,602	(98,272)	5,349
Balance at Dec. 31, 2011	571,394	257,630	0	458,139	(150,364)	5,989
Stockholders' Equity Attributable to Noncontrolling Interest [Roll Forward]
Net income	16,429			16,355		74
Other comprehensive income	5,037				5,195	(158)
Stock issued	5,250	5,250
Stock purchased	(4,304)	(1,542)				(2,762)
Advance payments	369		369
Dividends declared	(3,921)			(3,921)
Balance at Mar. 31, 2012	$ 590,254	$ 261,338	$ 369	$ 470,573	$ (145,169)	$ 3,143