CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Cash flows from operating activities:
Net income (loss)	$ 43,021	$ (368,969)	$ 513,368
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Net investment (gains) losses	144,297	(28,226)	60,525
Net realized and unrealized gains on other investments	(45,153)	(72,763)	(38,669)
Amortization of fixed maturities	24,663	43,292	65,921
Interest in income (loss) of equity method investments	495	8,402	2,094
Amortization of value of business acquired	172,332	50,104	0
Other amortization and depreciation	9,795	31,367	24,573
Share-based compensation expense, net of cash payments	34,346	12,667	52,211
Non-cash foreign exchange losses	0	24,149	0
Bargain purchase gain	0	(15,044)	0
Changes in:
Accrued interest receivable	(3,184)	(4,353)	(885)
Reinsurance recoverable balances on unpaid and paid losses	(766,690)	(131,160)	(176,532)
Deferred acquisition costs	(98,329)	(35,076)	33,212
Prepaid reinsurance premiums	(212,654)	(56,377)	(158,809)
Reserve for loss and loss expenses	442,839	1,004,578	54,476
Unearned premiums	29,760	(56,603)	198,938
Insurance and reinsurance balances, net	208,783	(81,831)	(209,895)
Other items	26,452	(64,928)	(13,804)
Net cash provided by operating activities	10,773	259,229	406,724
Purchases of:
Fixed maturities	(8,464,140)	(8,714,990)	(9,176,728)
Equity securities	(73,107)	(106,136)	(302,554)
Mortgage loans	(106,171)	(31,077)	(148,450)
Other investments	(180,126)	(153,150)	(190,370)
Equity method investments	0	(1,000)	(107,913)
Short-term investments	(305,670)	(41,609)	(190,747)
Proceeds from the sale of:
Fixed maturities	7,586,536	7,004,973	7,905,316
Equity securities	246,196	448,058	305,642
Other investments	361,030	260,943	215,578
Short-term investments	178,983	49,280	54,165
Proceeds from redemption of fixed maturities	1,241,214	2,009,982	1,492,588
Proceeds from redemption of short-term investments	45,831	119,427	36,546
Proceeds from the repayment of mortgage loans	133,081	56,435	5,040
Purchase of other assets	(25,103)	(42,685)	(27,149)
Purchase of subsidiaries, net	0	(466,941)	0
Net cash provided by (used in) investing activities	638,554	391,510	(129,036)
Cash flows from financing activities:
Net proceeds from issuance of debt	0	346,362	0
Repayment of notes payable	0	(67,242)	0
Net proceeds from issuance of preferred shares	0	0	531,945
Repurchase of common shares - open market	0	(261,180)	(495,426)
Taxes paid on withholding shares	(10,080)	(24,678)	(14,329)
Dividends paid - common shares	(133,502)	(135,032)	(132,323)
Repurchase of preferred shares	0	(351,074)	(51,769)
Dividends paid - preferred shares	(42,625)	(52,844)	(39,909)
Proceeds from issuance of common shares	0	0	224
Net cash used in financing activities	(186,207)	(545,688)	(201,587)
Effect of exchange rate changes on foreign currency cash, cash equivalents and restricted cash	3,114	17,228	(9,345)
Increase in cash, cash equivalents and restricted cash	466,234	122,279	66,756
Cash, cash equivalents and restricted cash - beginning of year	1,363,786	1,241,507	1,174,751
Cash, cash equivalents and restricted cash - end of year	1,830,020	1,363,786	1,241,507
Supplemental disclosures of cash flow information:
Income taxes paid	15,698	0	12,041
Interest paid	$ 64,822	$ 49,945	$ 48,875