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, 2013	$ 902,212	$ 1,770	$ 335,546	$ (155,801)	$ 692,337	$ 28,360
Beginning balance (in shares) at Dec. 31, 2013		17,709,876		3,511,380
Net income	27,968				27,968
Changes in other comprehensive income:
Change in net unrealized gain (loss) on investments	12,635					12,635
Change in net non-credit other-than-temporary impairment losses	56					56
Change in foreign currency translation gain (loss)	(7,739)					(7,739)
Total other comprehensive income	4,952					4,952
Shares issued under stock plan (in shares)		56,710
Shares issued under stock plan	(184)	6	(190)
Share-based compensation	1,886		1,886
Ending balance at Mar. 31, 2014	$ 936,834	$ 1,776	$ 337,242	$ (155,801)	$ 720,305	$ 33,312
Ending balance (in shares) at Mar. 31, 2014		17,766,586		3,511,380