Consolidated Statements Of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
OPERATING ACTIVITIES
Net income (loss)	$ 1,799,462	$ (130,353)	$ 400,758
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Deferred income tax expense (benefit)	323,385	2,729	(324,090)
Depreciation and amortization	269,239	227,846	203,871
Net investment losses (gains)	(1,601,722)	437,596	5,303
Net foreign exchange losses (gains)	2,265	(106,598)	(3,140)
Impairment of goodwill and intangible assets	0	199,198	0
Increase in receivables	(103,982)	(27,961)	(38,259)
Increase in deferred policy acquisition costs	(93,015)	(15,585)	(67,923)
Increase in unpaid losses and loss adjustment expenses, net	226,263	298,796	619,305
Decrease in life and annuity benefits	(52,159)	(50,541)	(55,647)
Increase in unearned premiums, net	354,116	62,879	197,706
Increase (decrease) in payables to insurance and reinsurance companies	65,460	(4,313)	(40,761)
Increase (decrease) in income taxes payable	36,938	53,730	(35,968)
Increase (decrease) in accrued expenses	24,432	(23,756)	(71,669)
Increase (decrease) in other liabilities	(9,528)	(5,637)	45,051
Other	32,966	(25,173)	23,992
Net Cash Provided By Operating Activities	1,274,120	892,857	858,529
INVESTING ACTIVITIES
Proceeds from sales of fixed maturities and equity securities	353,918	419,199	577,650
Proceeds from maturities, calls and prepayments of fixed maturities	772,336	551,808	1,129,895
Cost of fixed maturities and equity securities purchased	(955,970)	(1,545,913)	(1,176,281)
Net change in short-term investments	(95,867)	1,101,636	234,743
Cost of equity method investments	(257,663)	(8,864)	(13,023)
Additions to property and equipment	(123,376)	(106,593)	(74,652)
Acquisitions, net of cash acquired	(245,332)	(1,175,211)	(1,431,712)
Other	16,795	(33,301)	8,923
Net Cash Used By Investing Activities	(535,159)	(797,239)	(744,457)
FINANCING ACTIVITIES
Additions to senior long-term debt and other debt	1,645,182	206,949	664,657
Repayments of senior long-term debt and other debt	(1,103,674)	(289,199)	(259,972)
Premiums and fees related to early extinguishment of debt	(27,073)	0	0
Repurchases of common stock	(116,307)	(54,007)	(110,838)
Payment of contingent consideration	(14,113)	(15,914)	(5,018)
Purchase of noncontrolling interests	(9,754)	(13,523)	(18,334)
Distributions to noncontrolling interests	(8,992)	(9,164)	(7,899)
Other	(5,952)	(4,127)	(6,281)
Net Cash Provided (Used) By Financing Activities	359,317	(178,985)	256,315
Effect of foreign currency rate changes on cash, cash equivalents, restricted cash and restricted cash equivalents	5,643	(21,047)	45,295
Increase (decrease) in cash, cash equivalents, restricted cash and restricted cash equivalents	1,103,921	(104,414)	415,682
Cash, cash equivalents, restricted cash and restricted cash equivalents at beginning of year	2,396,432	2,500,846	2,085,164
CASH, CASH EQUIVALENTS, RESTRICTED CASH AND RESTRICTED CASH EQUIVALENTS AT END OF YEAR	$ 3,500,353	$ 2,396,432	$ 2,500,846