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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, 2016		$ 457	$ 52,468	$ 1,138,851	$ 29,598
Repurchases of common stock		(19)	(78,558)	(78,195)
Share-based compensation			26,095
Net issuance of common stock		5	(5)
Net income	$ 350,255			350,255
Dividends				(35,821)
Change in foreign currency translation adjustment, net of income tax expense (benefit)					17,188
Change in net unrealized investment gains (losses) not-other-than temporarily impaired					(3,166)
Change in net unrealized investment gains (losses) other-than-temporarily impaired					(52)
Balance, end of period at Dec. 31, 2017	$ 1,419,101	443		1,375,090	43,568
Dividends declared per share	$ 0.78
Cumulative effect from the adoption of new accounting standards, net				24,610	73
Repurchases of common stock		(21)	(26,702)	(190,134)
Share-based compensation			26,707
Net issuance of common stock		5	(5)
Net income	$ 324,094			324,094
Dividends				(44,140)
Change in foreign currency translation adjustment, net of income tax expense (benefit)					(25,059)
Change in net unrealized investment gains (losses) not-other-than temporarily impaired					(47,012)
Change in net unrealized investment gains (losses) other-than-temporarily impaired					(4)
Balance, end of period at Dec. 31, 2018	$ 1,461,513	427		1,489,520	(28,434)
Dividends declared per share	$ 1.00
Repurchases of common stock		(19)	(27,204)	(205,000)
Share-based compensation			27,208
Net issuance of common stock		4	$ (4)
Net income	$ 366,391			366,391
Dividends				(57,630)
Change in foreign currency translation adjustment, net of income tax expense (benefit)					15,299
Change in net unrealized investment gains (losses) not-other-than temporarily impaired					71,848
Change in net unrealized investment gains (losses) other-than-temporarily impaired					85
Balance, end of period at Dec. 31, 2019	$ 1,652,491	$ 412		$ 1,593,281	$ 58,798
Dividends declared per share	$ 1.36