Unaudited Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
Operating Activities
Net income	$ 422,731	$ 473,134
Adjustments to reconcile net income to net cash provided by operating activities:
Net realized (gains) losses	177,442	(74,985)
Net impairment losses recognized in earnings	632	3,537
Equity in net income or loss of investment funds accounted for using the equity method and other income or loss	(13,543)	(47,529)
Amortization of intangible assets	53,208	62,118
Share-based compensation	35,419	42,739
Changes in:
Reserve for losses and loss adjustment expenses, net of unpaid losses and loss adjustment expenses recoverable	(77,891)	180,342
Unearned premiums, net of ceded unearned premiums	139,778	167,064
Premiums receivable	(236,950)	(222,498)
Deferred acquisition costs	(35,111)	(53,553)
Reinsurance balances payable	88,961	50,112
Other items, net	(57,790)	(46,946)
Net cash provided by operating activities	496,886	533,535
Investing Activities
Purchases of fixed maturity investments	(16,867,570)	(19,899,326)
Purchases of equity securities	(679,663)	(400,155)
Purchases of other investments	(1,017,147)	(883,704)
Proceeds from sales of fixed maturity investments	16,090,543	19,611,680
Proceeds from sales of equity securities	622,068	473,064
Proceeds from sales, redemptions and maturities of other investments	773,298	614,494
Proceeds from redemptions and maturities of fixed maturity investments	511,448	447,941
Net settlements of derivative instruments	4,498	(5,984)
Net sales (purchases) of short-term investments	451,901	(445,203)
Change in cash collateral related to securities lending	176,304	175,693
Purchases of fixed assets	(13,242)	(11,103)
Other	49,961	33,488
Net cash provided by (used for) investing activities	102,399	(289,115)
Financing Activities
Redemption of preferred shares	(92,555)	0
Purchases of common shares under share repurchase program	(173,575)	0
Proceeds from common shares issued, net	(13,851)	(6,838)
Proceeds from borrowings	130,579	0
Repayments of borrowings	(373,000)	(72,000)
Change in cash collateral related to securities lending	(176,304)	(175,693)
Dividends paid to redeemable noncontrolling interests	(8,994)	(8,994)
Other	(4,489)	(41,698)
Preferred dividends paid	(20,840)	(22,567)
Net cash provided by (used for) financing activities	(733,029)	(327,790)
Effects of exchange rate changes on foreign currency cash and restricted cash	(10,431)	9,616
Increase (decrease) in cash and restricted cash	(144,175)	(73,754)
Cash and restricted cash, beginning of year	727,284	969,569
Cash and restricted cash, end of period	$ 583,109	$ 895,815