Consolidated Statements of Stockholders' Equity (USD $) In Thousands, except Share data, unless otherwise specified	Total	Common Stock	Additional Paid-in Capital	Treasury Stock	Retained Earnings	Accumulated Other Comprehensive Income (Loss)
Beginning Balance at Dec. 31, 2012	$ 879,485	$ 1,755	$ 329,452	$ (155,801)	$ 628,871	$ 75,208
Beginning Balance (in shares) at Dec. 31, 2012		17,558,046		3,511,380
Net income	13,910				13,910
Changes in other comprehensive income:
Change in net unrealized gain (loss) on investments	(2,034)					(2,034)
Change in net non-credit other-than-temporary impairment losses	279					279
Change in foreign currency translation gain (loss)	2,630					2,630
Other comprehensive income (loss)	875					875
Shares issued under stock plan (in shares)		83,311
Shares issued under stock plan	1,130	8	1,122
Share-based compensation	1,358		1,358
Ending Balance at Mar. 31, 2013	$ 896,758	$ 1,763	$ 331,932	$ (155,801)	$ 642,781	$ 76,083
Ending Balance (in shares) at Mar. 31, 2013		17,641,357		3,511,380