Consolidated Statements of Changes in Shareholders' Equity - USD ($) $ in Thousands	Total	Additional Paid-in Capital	Accumulated other comprehensive income, net of deferred income tax	Retained Earnings	Treasury Shares	Ordinary Shares A	Ordinary Shares A Treasury Shares	Ordinary Shares B
Number at Dec. 31, 2014					3,064,815	16,331,577		12,061,370
Ordinary shares issued under share incentive plans						121,812
A ordinary shares purchased							11,895
Ordinary shares issued to directors						36,321
Elimination of shares indirectly owned by subsidiary							34,085
B ordinary shares converted to A ordinary shares						7,928,004		7,928,004
Ordinary shares redeemed						(8,260,870)
Ordinary shares issued in connection with American Reliable acquisition						267,702
Number at Dec. 31, 2015					3,110,795	16,424,546		4,133,366
Balance at Dec. 31, 2014		$ 519,590	$ 23,384	$ 466,717	$ (101,404)	$ 2		$ 1
Other comprehensive income (loss):
Change in unrealized holding gains (losses)			(19,436)
Change in other than temporary impairment losses recognized in other comprehensive income			(10)
Unrealized foreign currency translation gains (losses)			140
Other comprehensive income (loss), net of tax			(19,306)
A ordinary shares purchased, at cost							$ (333)
Share compensation plans		10,272
Ordinary shares redeemed				(189,770)
Elimination of shares indirectly owned by subsidiary							$ (706)
Tax benefit on share-based compensation expense		10
Net income				41,469
Balance at Dec. 31, 2015	$ 749,926	529,872	4,078	318,416	$ (102,443)	$ 2		$ 1
Ordinary shares issued under share incentive plans						115,712
A ordinary shares purchased							28,099
Ordinary shares issued to directors						19,614
Number at Jun. 30, 2016					3,138,894	16,559,872		4,133,366
Other comprehensive income (loss):
Change in unrealized holding gains (losses)			18,312
Change in other than temporary impairment losses recognized in other comprehensive income			(1)
Unrealized foreign currency translation gains (losses)	(313)		(313)
Other comprehensive income (loss), net of tax	17,998		17,998
A ordinary shares purchased, at cost							$ (805)
Share compensation plans		1,543
Tax benefit on share-based compensation expense		127
Net income	1,960			1,960
Balance at Jun. 30, 2016	$ 770,749	$ 531,542	$ 22,076	$ 320,376	$ (103,248)	$ 2		$ 1