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	44,829				44,829
Changes in other comprehensive income:
Change in net unrealized gain (loss) on investments	25,923					25,923
Change in net non-credit other- than-temporary impairment losses	130					130
Change in foreign currency translation gain (loss)	(4,997)					(4,997)
Total other comprehensive income	21,056					21,056
Shares issued under stock plan (in shares)		62,483
Shares issued under stock plan	(386)	6	(392)
Share-based compensation	4,369		4,369
Ending balance at Jun. 30, 2014	$ 972,080	$ 1,776	$ 339,523	$ (155,801)	$ 737,166	$ 49,416
Ending balance (in shares) at Jun. 30, 2014		17,772,359		3,511,380