Consolidated Statements Of Changes In Shareholders' Equity - USD ($) $ in Thousands	Total	Preference shares	Common shares	Additional paid-in capital	Accumulated other comprehensive income	Retained earnings
Beginning of period at Dec. 31, 2013		$ 400,000	$ 43,646	$ 0	$ 4,131	$ 3,456,607
Statement of Changes in Stockholders' Equity
Issuance of shares			0	0
Repurchase of shares			(5,355)	(11,702)		(497,175)
Change in redeemable noncontrolling interest				1,274
Exercise of options and issuance of restricted stock awards			151	10,428
Change in net unrealized gains on investments	$ 715				(715)
Net income	686,256					686,256
Net income attributable to noncontrolling interests	(153,538)					(153,538)
Dividends on common shares						(45,912)
Dividends on preference shares	(22,381)					(22,381)
End of period at Dec. 31, 2014		400,000	38,442	0	3,416	3,423,857
Statement of Changes in Stockholders' Equity
Total shareholders’ equity	3,865,715
Issuance of shares			7,435	754,384
Repurchase of shares			(2,473)	(257,401)		0
Change in redeemable noncontrolling interest				(762)
Exercise of options and issuance of restricted stock awards			297	11,453
Change in net unrealized gains on investments	1,308				(1,308)
Net income	542,242					542,242
Net income attributable to noncontrolling interests	(111,050)					(111,050)
Dividends on common shares						(53,967)
Dividends on preference shares	(22,381)					(22,381)
End of period at Dec. 31, 2015	4,732,184	400,000	43,701	507,674	2,108	3,778,701
Statement of Changes in Stockholders' Equity
Total shareholders’ equity	4,732,184
Issuance of shares			0	0
Repurchase of shares			(2,741)	(306,693)		0
Change in redeemable noncontrolling interest				(1,655)
Exercise of options and issuance of restricted stock awards			227	17,232
Change in net unrealized gains on investments	975				(975)
Net income	630,048					630,048
Net income attributable to noncontrolling interests	(127,086)
Dividends on common shares						(51,583)
Dividends on preference shares	(22,381)
End of period at Dec. 31, 2016	4,866,577	$ 400,000	$ 41,187	$ 216,558	$ 1,133	$ 4,207,699
Statement of Changes in Stockholders' Equity
Total shareholders’ equity	$ 4,866,577