Consolidated Statement of Stockholders' Equity - 9 months ended Sep. 30, 2018 - 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	36,530		7,023
Net Income		$ 67,607				67,607
Dividends Declared		(6,234)				(6,234)
Changes in Other Comprehensive Income:
Change in Net Unrealized Loss on Available-For-Sale Investments		(53,405)					(53,405)
Change in Net Non-Credit Other-Than- Temporary Impairment Losses		(56)					(56)
Change in Foreign Currency Translation Loss		(4,420)					(4,420)
Other Comprehensive Income (Loss)		(57,881)					(57,881)
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]	(5,042)	$ 27	(5,069)
Shares issued (in shares)	[1]		265
Share-Based Compensation		7,413		7,413
Ending Balance at Sep. 30, 2018		$ 1,231,828	$ 3,677	$ 379,212	$ (155,801)	$ 1,047,673	$ (42,933)
Ending Balance (in shares) at Sep. 30, 2018		36,795	36,795		7,023

[1] Includes shares issued under the Second Amended and Restated 2005 Stock Incentive Plan to Directors and the Employee Stock Purchase Plan.