Consolidated Statements of Changes in Shareholders’ Equity (USD $) In Thousands, unless otherwise specified	Total	Common Stock	Retained Earnings	Accumulated Other Comprehensive Loss	Noncontrolling Interests
Balance at Dec. 31, 2009	$ 538,169	$ 211,970	$ 423,920	$ (102,599)	$ 4,878
Stockholders' Equity Attributable to Noncontrolling Interest [Roll Forward]
Net income	42,293		41,998		295
Other comprehensive income	382			256	126
Stock issued	9,799	9,799
Stock purchased	(10,599)	(10,448)			(151)
Dividends declared	(21,237)	21,079	(42,316)
Balance at Dec. 31, 2010	558,807	232,400	423,602	(102,343)	5,148
Stockholders' Equity Attributable to Noncontrolling Interest [Roll Forward]
Net income	81,891		81,425		466
Other comprehensive income	(48,049)			(48,021)	(28)
Stock issued	11,633	11,121			512
Stock purchased	(9,373)	(9,264)			(109)
Dividends declared	(23,515)	23,373	(46,888)
Balance at Dec. 31, 2011	571,394	257,630	458,139	(150,364)	5,989
Stockholders' Equity Attributable to Noncontrolling Interest [Roll Forward]
Net income	86,598		86,291		307
Other comprehensive income	(16,631)			(16,450)	(181)
Stock issued	11,925	11,925
Stock purchased	(14,035)	(11,172)			(2,863)
Dividends declared	(39,035)	51,625	(90,660)
Balance at Dec. 31, 2012	$ 600,216	$ 310,008	$ 453,770	$ (166,814)	$ 3,252