Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Cash flows from operating activities
Net (losses) earnings	$ (361,472)	$ 447,902
Adjustments to reconcile net earnings to net cash provided by (used in) operating activities:
Depreciation and amortization	33,158	27,732
Change in the fair value of equity securities	522,976	(392,353)
Net realized capital (gains) losses	(13,026)	(4,442)
Credit losses for available for sale securities	31,375
Credit losses for available for sale securities		10,020
(Increase) decrease in reinsurance recoverables, net of reinsurance payable	49,693	165,434
(Increase) decrease in premium balances receivable	(143,970)	(103,538)
(Increase) decrease in ceded unearned premiums	(18,020)	(9,849)
(Increase) decrease in deferred acquisition costs	(18,463)	(23,537)
(Increase) decrease in funds held under reinsurance agreements	(23,757)	19,984
Increase (decrease) in unearned premiums	102,239	101,816
Increase (decrease) in loss and loss adjustment expenses	138,079	(395,170)
Change in unrealized foreign currency exchange rate losses (gains)	80,530	1,070
Other, net	(386,627)	88,546
Net adjustments	354,187	(514,287)
Net cash provided by (used in) operating activities	(7,285)	(66,385)
Cash flows from investing activities
Purchases of debt securities	(1,993,449)	(2,460,366)
Purchases of equity securities	(331,453)	(69,729)
Sales of debt securities	1,960,691	987,132
Maturities and redemptions of debt securities	459,655	235,521
Sales of equity securities	602,627	1,510,222
Net (purchases) sales of short-term investments	378,854	(376,414)
Net (purchases) sales and maturities of commercial mortgage loans	3,551	29
(Purchases) sales of property and equipment	(8,840)	(12,956)
Purchases of affiliates and subsidiaries, net of cash acquired	(26,383)	1,157
Other, net	(152,416)	73,423
Net cash provided by (used in) investing activities	892,837	(111,981)
Cash flows from financing activities
Repayment of senior notes	(307,095)
Treasury stock acquisitions	(44,268)	(80,486)
Increase (decrease) in other debt	62,659	8,178
Cash dividends paid	(215,013)
Other, net	3,664	(11,421)
Net cash provided by (used in) financing activities	(500,053)	(83,729)
Effect of foreign exchange rate changes on cash	(9,412)	1,396
Net increase (decrease) in cash	376,087	(260,699)
Cash at beginning of period	1,179,098	1,038,763
Cash at end of period	1,555,185	778,064
Supplemental disclosures of cash flow information
Interest paid	17,065	19,368
Income taxes paid (refund received)	$ 24,604	$ (39,657)