Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Operating Activities
Net income	$ 1,693,300	$ 727,821	$ 629,709
Adjustments to reconcile net income to net cash provided by operating activities:
Net realized (gains) losses	(381,132)	387,550	(174,517)
Net impairment losses recognized in earnings	3,165	2,829	7,138
Equity in net income or loss of investments accounted for using the equity method and other income or loss	(14,013)	36,694	(79,540)
Amortization of intangible assets	82,104	105,670	125,778
Share-based compensation	66,417	55,776	67,798
Changes in:
Reserve for losses and loss adjustment expenses, net of unpaid losses and loss adjustment expenses recoverable	489,981	243,734	614,534
Unearned premiums, net of ceded unearned premiums	252,569	114,772	116,841
Premiums receivable	(237,752)	(211,296)	(31,405)
Deferred acquisition costs, net	(47,260)	(37,847)	(78,378)
Reinsurance balances payable	182,132	73,438	8,529
Other items, net	(41,052)	60,181	(111,609)
Net cash provided by operating activities	2,048,459	1,559,322	1,094,878
Investing Activities
Purchases of fixed maturity investments	(30,053,777)	(33,327,660)	(36,806,913)
Purchases of equity securities	(811,967)	(1,001,149)	(1,021,016)
Purchases of other investments	(1,470,545)	(2,014,622)	(2,020,624)
Proceeds from the sale of fixed maturity investments	28,595,865	31,513,271	35,686,779
Proceeds from sales of equity securities	429,818	1,118,445	1,056,401
Proceeds from sales, redemptions and maturities of other investments	1,209,559	1,561,958	1,528,617
Proceeds from redemptions and maturities of fixed maturity investments	643,265	892,755	907,417
Net settlements of derivative instruments	59,982	44,699	(28,563)
Net (purchases) sales of short-term investments	39,833	485,473	(734,554)
Change in cash collateral related to securities lending	(62,193)	180,883	12,540
Purchases of fixed assets	(37,837)	(29,809)	(22,841)
Other	(348,486)	21,736	90,875
Net cash provided by (used for) investing activities	(1,806,483)	(554,020)	(1,351,882)
Financing Activities
Proceeds from issuance of preferred shares, net	0	0	319,694
Redemption of preferred shares	0	(92,555)	(230,000)
Purchases of common shares under share repurchase program	(2,871)	(282,762)	0
Proceeds from common shares issued, net	6,203	(7,608)	(21,048)
Proceeds from borrowings	200,083	218,259	253,415
Repayments of borrowings	(49,182)	(576,401)	(197,000)
Change in cash collateral related to securities lending	62,193	(180,883)	(12,540)
Change in third party investment in non-redeemable noncontrolling interests	(75,056)	0	0
Change in third party investment in redeemable noncontrolling interests	(161,882)	0	0
Dividends paid to redeemable noncontrolling interests	(12,515)	(17,989)	(17,989)
Other	(6,023)	(7,226)	(51,896)
Preferred dividends paid	(41,612)	(41,645)	(46,041)
Net cash provided by (used for) financing activities	(80,662)	(988,810)	(3,405)
Effects of exchange rate changes on foreign currency cash and restricted cash	17,741	(19,133)	18,124
Increase (decrease) in cash and restricted cash	179,055	(2,641)	(242,285)
Cash and restricted cash, beginning of year	724,643	727,284	969,569
Cash and restricted cash, end of year	903,698	724,643	727,284
Supplemental cash flow information
Income taxes paid (received)	109,463	(980)	51,781
Interest paid	$ 126,945	$ 119,775	$ 117,374