CONDENSED CONSOLIDATED STATEMENTS OF CHANGES IN SHAREHOLDERS' EQUITY - USD ($) $ in Thousands	Total	Preference shares [Member]	Common shares [Member]	Additional paid-in capital [Member]	Accumulated other comprehensive income [Member]	Retained earnings [Member]	Treasury shares [Member]	Noncontrolling interest in subsidiaries [Member]
Beginning balance at Dec. 31, 2013		$ 315,000	$ 736	$ 574,522	$ 25,784	$ 211,602	$ (3,801)	$ 452
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Acquisition of subsidiary								0
Dividend paid to noncontrolling interest								(31)
Exercise of options and issuance of common shares			2	324
Share based compensation expense				965
Change in net unrealized (losses) gains on investments, net of reclassification adjustment and deferred income tax expense					91,686
Foreign currency translation adjustment					480			(3)
Net income (loss)	$ 33,976					33,910		66
Dividends on preference shares						(12,168)
Dividends on common shares						(16,049)
Shares repurchased for treasury							(66)
Ending balance at Jun. 30, 2014	1,223,411	315,000	738	575,811	117,950	217,295	(3,867)	484
Beginning balance at Dec. 31, 2014	1,241,166	315,000	739	578,445	95,293	255,084	(3,867)	472
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Acquisition of subsidiary								1,710
Dividend paid to noncontrolling interest								(25)
Exercise of options and issuance of common shares			7	2,619
Share based compensation expense				1,548
Change in net unrealized (losses) gains on investments, net of reclassification adjustment and deferred income tax expense					(63,464)
Foreign currency translation adjustment					9,104			(47)
Net income (loss)	65,045					65,092		(47)
Dividends on preference shares						(12,168)
Dividends on common shares						(19,124)
Shares repurchased for treasury							(654)
Ending balance at Jun. 30, 2015	$ 1,225,717	$ 315,000	$ 746	$ 582,612	$ 40,933	$ 288,884	$ (4,521)	$ 2,063