CONSOLIDATED CONDENSED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) (Parenthetical) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Statement of Comprehensive Income [Abstract]
Change in net unrealized gains (losses) on investments, income tax	$ (112,404)	$ 154,403	$ (265,037)	$ 240,871
Reclassification adjustment for investment amounts included in net income, income tax	(1,150)	1,355	(969)	(143)
Change in net unrealized gains (losses) relating to other-than-temporary impaired investments for which a portion has been recognized in earnings, income tax	3	1,391	6	3,385
Change in accumulated (loss) gain - derivatives, income tax	623	(64)	752	(426)
Reclassification adjustment for derivative amounts included in net income, income tax	$ 43	$ 53	$ 67	$ 125