Condensed Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock [Member]	Paid-in Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]
Balance, beginning of period at Dec. 31, 2015		$ 483	$ 180,250	$ 952,804	$ 12,235
Repurchases of common stock		(21)	(94,294)
Share-based compensation			16,873
Net issuance of common stock		4	(4)
Net income	$ 104,502			104,502
Dividends				(16,446)
Change in foreign currency translation adjustment, net of income tax expense (benefit)					14,710
Change in net unrealized investment gains (losses) not-other-than temporarily impaired, net of income tax expense (benefit)					36,365
Change in net unrealized investment losses other-than-temporarily impaired, net of income tax expense (benefit)					5
Balance, end of period at Jun. 30, 2016	1,207,466	466	102,825	1,040,860	63,315
Balance, beginning of period at Dec. 31, 2016	1,221,374	457	52,468	1,138,851	29,598
Repurchases of common stock		(11)	(69,556)	(11,972)
Share-based compensation			17,092
Net issuance of common stock		4	$ (4)
Net income	115,176			115,176
Dividends				(17,680)
Change in foreign currency translation adjustment, net of income tax expense (benefit)					7,792
Change in net unrealized investment gains (losses) not-other-than temporarily impaired, net of income tax expense (benefit)					7,031
Change in net unrealized investment losses other-than-temporarily impaired, net of income tax expense (benefit)					7
Balance, end of period at Jun. 30, 2017	$ 1,269,253	$ 450		$ 1,224,375	$ 44,428