Unaudited Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Operating Activities
Net income (loss)	$ 377,715	$ 981,343
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Net realized (gains) losses	(194,776)	(262,935)
Equity in net income or loss of investment funds accounted for using the equity method and other income or loss	125,384	(45,720)
Amortization of intangible assets	33,120	40,211
Share-based compensation	41,912	41,537
Changes in:
Reserve for losses and loss adjustment expenses, net of unpaid losses and loss adjustment expenses recoverable	1,158,446	154,396
Unearned premiums, net of ceded unearned premiums	395,759	137,564
Premiums receivable	(463,638)	(302,050)
Deferred acquisition costs	(92,437)	(24,790)
Reinsurance balances payable	132,161	139,415
Other items, net	(192,066)	(146,447)
Net cash provided by (used for) operating activities	1,321,580	712,524
Investing Activities
Purchases of fixed maturity investments	(25,410,849)	(16,332,646)
Purchases of equity securities	(1,025,149)	(431,939)
Purchases of other investments	(501,692)	(677,063)
Proceeds from sales of fixed maturity investments	24,833,030	15,632,482
Proceeds from sales of equity securities	580,346	176,701
Proceeds from sales, redemptions and maturities of other investments	472,188	534,698
Proceeds from redemptions and maturities of fixed maturity investments	369,240	244,949
Net settlements of derivative instruments	150,471	87,701
Net (purchases) sales of short-term investments	(1,323,363)	201,520
Change in cash collateral related to securities lending	54,596	7,590
Purchases of fixed assets	(17,687)	(16,359)
Other	8,679	(174,578)
Net cash provided by (used for) investing activities	(1,810,190)	(746,944)
Financing Activities
Purchases of common shares under share repurchase program	(75,486)	(2,871)
Proceeds from common shares issued, net	(9,661)	(557)
Proceeds from borrowings	1,004,918	62,800
Repayments of borrowings	(165,000)	(27,538)
Change in cash collateral related to securities lending	(54,596)	(7,590)
Third party investment in non-redeemable noncontrolling interests	(2,867)	0
Dividends paid to redeemable noncontrolling interests	(2,540)	(8,994)
Other	(2,625)	(3,529)
Preferred dividends paid	(20,806)	(20,806)
Net cash provided by (used for) financing activities	671,337	(9,085)
Effects of exchange rate changes on foreign currency cash and restricted cash	(21,742)	1,937
Increase (decrease) in cash and restricted cash	160,985	(41,568)
Cash and restricted cash, beginning of year	903,698	724,643
Cash and restricted cash, end of period	$ 1,064,683	$ 683,075