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, 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 (loss)	(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 (loss)	(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
Stockholders' Equity Attributable to Noncontrolling Interest [Roll Forward]
Net income	81,274		81,063		211
Other comprehensive income (loss)	26,285			26,451	(166)
Stock issued	13,327	12,839			488
Stock purchased	(12,920)	(12,772)			(148)
Dividends declared	(37,401)	7,692	(45,093)
Balance at Dec. 31, 2013	$ 670,781	$ 317,767	$ 489,740	$ (140,363)	$ 3,637