Consolidated Statement 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, 2017		$ 1,225,965	$ 3,650	$ 376,868	$ (155,801)	$ 981,380	$ 19,868
Beginning Balance (in shares) at Dec. 31, 2017			36,530		7,023
Net Income (Loss)		30,878				30,878
Dividends Declared		(2,069)				(2,069)
Changes in Other Comprehensive Income:
Change in Net Unrealized Gain (Loss) on Available-For-Sale Investments		(36,038)					(36,038)
Change in Net Non-Credit Other-Than- Temporary Impairment Losses		(30)					(30)
Change in Foreign Currency Translation Gain		2,228					2,228
Other Comprehensive Income (Loss)		(33,840)					(33,840)
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	[1]	(4,968)	$ 20	(4,988)
Shares issued (in shares)	[1]		203
Share-Based Compensation		986		986
Ending Balance at Mar. 31, 2018		1,216,952	$ 3,670	372,866	$ (155,801)	1,015,109	(18,892)
Ending Balance (in shares) at Mar. 31, 2018			36,733		7,023
Beginning Balance at Dec. 31, 2018		$ 1,186,850	$ 3,678	378,274	$ (155,801)	1,012,220	(51,521)
Beginning Balance (in shares) at Dec. 31, 2018		36,805	36,805		7,023
Net Income (Loss)		$ (1,738)				(1,738)
Dividends Declared		(2,087)				(2,087)
Changes in Other Comprehensive Income:
Change in Net Unrealized Gain (Loss) on Available-For-Sale Investments		46,478					46,478
Change in Net Non-Credit Other-Than- Temporary Impairment Losses		(16)					(16)
Change in Foreign Currency Translation Gain		3,821					3,821
Other Comprehensive Income (Loss)		50,283					50,283
Shares Issued	[1]	(5,219)	$ 18	(5,237)
Shares issued (in shares)	[1]		188
Share-Based Compensation		2,294		2,294
Ending Balance at Mar. 31, 2019		$ 1,230,383	$ 3,696	$ 375,331	$ (155,801)	$ 1,008,395	$ (1,238)
Ending Balance (in shares) at Mar. 31, 2019		36,993	36,993		7,023

[1] Includes shares issued under the Second Amended and Restated 2005 Stock Incentive Plan to Directors, the Employee Stock Purchase Plan, and the impact of employee tax withholding on stock compensation.