Condensed Consolidated Statements of Changes in Shareholders’ Equity (USD $) In Thousands	Total	Common Stock	Common Stock Subscribed, Unissued	Retained Earnings	Accumulated Other Comprehensive Loss	Noncontrolling Interests
Balance at Dec. 31, 2009	$ 538,169	$ 211,970	$ 0	$ 423,920	$ (102,599)	$ 4,878
Stockholders' Equity Attributable to Noncontrolling Interest [Roll Forward]
Net income	13,132			13,034		98
Foreign currency translation	7				7
Unrealized gain (loss) from interest rate swap (net of tax)	(167)				(167)
Pension and postretirement benefits liability adjustment (net of tax)	4,480				4,480
Comprehensive income	17,452
Stock issued	6,054	6,054
Stock purchased	(5,934)	(5,851)				(83)
Advance payments	343		343
Dividends declared	(6,369)			(6,369)
Balance at Jun. 30, 2010	549,715	212,173	343	430,585	(98,279)	4,893
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	35,649			35,449		200
Foreign currency translation	1,508				1,440	68
Unrealized gain (loss) from interest rate swap (net of tax)	389				389
Pension and postretirement benefits liability adjustment (net of tax)	4,673				4,673
Comprehensive income	42,219
Stock issued	6,926	6,926
Stock purchased	(4,551)	(4,488)				(63)
Advance payments	377		377
Dividends declared	(7,053)			(7,053)
Balance at Jun. 30, 2011	$ 596,725	$ 234,838	$ 377	$ 451,998	$ (95,841)	$ 5,353