Consolidated Statements of Shareholders' Equity (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Shareholders' equity at beginning of year	$ 368,735	$ 372,943	$ 330,067
Comprehensive income:
Net income (loss)	(28,175)	25,015	44,802
Change in unrealized gains (losses) on investments	(7,302)	2,008	12,476
Foreign exchange adjustment	(230)	441	1,001
Total comprehensive income (loss)	(35,707)	27,464	58,279
Other changes affecting shareholders' equity:
Cash dividends paid to shareholders	(14,846)	(33,212)	(14,744)
Issuance of common stock	879	1,540	221
Cost of treasury shares in excess of original issue proceeds	0	0	(880)
Total other changes	(13,967)	(31,672)	(15,403)
Total changes	(49,674)	(4,208)	42,876
Shareholders' equity at end of year:	$ 319,061	$ 368,735	$ 372,943