Consolidated Statements of Stockholders' Equity - USD ($) shares in Thousands, $ in Thousands		Total	Common Stock	Additional Paid-in Capital	Treasury Stock	Retained Earnings	Accumulated Other Comprehensive Income (Loss)
Beginning Balance at Dec. 31, 2015		$ 1,096,148	$ 3,586	$ 356,036	$ (155,801)	$ 868,723	$ 23,604
Beginning Balance (in shares) at Dec. 31, 2015			35,885		7,023
Net Income		82,726				82,726
Dividends Declared	[1]	(3,930)				(3,930)
Changes in Comprehensive Income (Loss):
Change in Net Unrealized Loss on Investments		(5,355)					(5,355)
Change in Net Non-Credit Other-Than- Temporary Impairment Losses		(50)					(50)
Change in Foreign Currency Translation Loss		(9,324)					(9,324)
Change in Benefit Plans' Obligations		0
Other Comprehensive Income (Loss)		(14,729)					(14,729)
Shares Issued	[2]	349	$ 26	323
Shares Issued (in shares)	[2]		262
Share-Based Compensation		17,624		17,624
Ending Balance at Dec. 31, 2016		1,178,188	$ 3,612	373,983	$ (155,801)	947,519	8,875
Ending Balance (in shares) at Dec. 31, 2016			36,147		7,023
Net Income		40,494				40,494
Dividends Declared	[1]	(6,633)				(6,633)
Changes in Comprehensive Income (Loss):
Change in Net Unrealized Loss on Investments		9,023					9,023
Change in Net Non-Credit Other-Than- Temporary Impairment Losses		40					40
Change in Foreign Currency Translation Loss		1,930					1,930
Change in Benefit Plans' Obligations		0
Other Comprehensive Income (Loss)		10,993					10,993
Shares Issued	[2]	(10,906)	$ 38	(10,944)
Shares Issued (in shares)	[2]		383
Share-Based Compensation		13,829		13,829
Ending Balance at Dec. 31, 2017		$ 1,225,965	$ 3,650	376,868	$ (155,801)	981,380	19,868
Ending Balance (in shares) at Dec. 31, 2017		36,530	36,530		7,023
Net Income		$ 34,239				34,239
Dividends Declared	[1]	(8,319)				(8,319)
Changes in Comprehensive Income (Loss):
Change in Net Unrealized Loss on Investments		(56,605)					(56,605)
Change in Net Non-Credit Other-Than- Temporary Impairment Losses		(93)					(93)
Change in Foreign Currency Translation Loss		(9,567)					(9,567)
Change in Benefit Plans' Obligations		(204)					(204)
Other Comprehensive Income (Loss)		(66,469)					(66,469)
Cumulative Effect of Adoption of ASU at January 1st, Net of Tax | ASU 2016-01						7,748	(7,748)
Cumulative Effect of Adoption of ASU at January 1st, Net of Tax | Accounting Standards Update 2018-02						(2,828)	2,828
Shares Issued	[2]	(5,352)	$ 28	(5,380)
Shares Issued (in shares)	[2]		275
Share-Based Compensation		6,786		6,786
Ending Balance at Dec. 31, 2018		$ 1,186,850	$ 3,678	$ 378,274	$ (155,801)	$ 1,012,220	$ (51,521)
Ending Balance (in shares) at Dec. 31, 2018		36,805	36,805		7,023

[1] Dividends Declared were $0.28 per share, $0.225 per share and $0.135 per share for the years ended December 31, 2018, 2017 and 2016, respectively.

[2] Includes shares issued under the Second Amended and Restated 2005 Stock Incentive Plan, to directors and the Employees Stock Purchase Plan.