CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Cash flows from operating activities:
Net income	$ 513,368	$ 641,631	$ 804,564
Adjustments to reconcile net income to net cash provided by operating activities:
Net realized investment (gains) losses	60,525	138,491	(132,108)
Net realized and unrealized gains on other investments	(38,669)	(20,148)	(57,621)
Amortization of fixed maturities	65,921	97,223	113,879
Interest in loss of equity method investments	2,094	0	0
Other amortization and depreciation	24,573	26,341	24,970
Share-based compensation expense, net of cash payments	52,211	43,052	63,237
Changes in:
Accrued interest receivable	(885)	8,908	13,788
Reinsurance recoverable balances	(176,532)	(214,992)	(16,204)
Deferred acquisition costs	33,212	(4,744)	(11,026)
Prepaid reinsurance premiums	(158,809)	(46,955)	(25,185)
Reserve for loss and loss expenses	54,476	151,011	46,903
Unearned premiums	198,938	29,841	58,376
Insurance and reinsurance balances, net	(209,895)	(74,578)	(102,593)
Other items	(13,804)	16,119	81,202
Net cash provided by operating activities	406,724	791,200	862,182
Purchases of:
Fixed maturities	(9,176,728)	(11,011,979)	(12,047,004)
Equity securities	(302,554)	(356,617)	(564,562)
Mortgage loans	(148,450)	(206,191)	0
Other investments	(190,370)	(83,561)	(75,542)
Equity method investments	(107,913)	0	0
Short-term investments	(190,747)	(80,069)	(669,494)
Proceeds from the sale of:
Fixed maturities	7,905,316	9,432,226	10,799,112
Equity securities	305,642	275,357	740,900
Other investments	215,578	252,418	213,508
Short-term investments	54,165	125,311	526,460
Proceeds from redemption of fixed maturities	1,492,588	1,407,806	1,086,244
Proceeds from redemption of short-term investments	36,546	23,687	80,474
Proceeds from the repayment of mortgage loans	5,040	0	0
Purchase of other assets	(27,149)	(33,683)	(20,857)
Change in restricted cash and cash equivalents	(15,395)	29,598	(223,315)
Net cash used in investing activities	(144,431)	(225,697)	(154,076)
Cash flows from financing activities:
Net proceeds from issuance of preferred shares	531,945	0	0
Repurchase of common shares	(509,755)	(332,252)	(543,202)
Dividends paid - common shares	(132,323)	(118,652)	(117,619)
Repurchase of preferred shares	(51,769)	0	0
Dividends paid - preferred shares	(39,909)	(40,088)	(40,088)
Proceeds from issuance of common shares	224	3,986	5,550
Net proceeds from issuance of senior notes	0	0	494,344
Redemption of senior notes	0	0	(500,000)
Sales of shares to noncontrolling interests	0	0	25,000
Return of capital to noncontrolling interests	0	0	(10,000)
Net cash used in financing activities	(201,587)	(487,006)	(686,015)
Effect of exchange rate changes on foreign currency cash and cash equivalents	(9,345)	(12,194)	(23,587)
Increase (decrease) in cash and cash equivalents	51,361	66,303	(1,496)
Cash and cash equivalents - beginning of year	988,133	921,830	923,326
Cash and cash equivalents - end of year	1,039,494	988,133	921,830
Supplemental disclosures of cash flow information:
Income taxes paid	12,041	12,661	7,654
Interest paid	48,875	$ 48,875	$ 68,850
Consideration transferred reinsurance	170,000
Transfer from Investments	$ 92,000