Condensed Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013
Cash flows from operating activities
Net income	$ 586,678	$ 59,982
Adjustments to reconcile net income to net cash provided by operating activities:
Amortization of net premium on investments	54,783	82,147
Amortization of intangible assets	14,005	14,091
Net realized and unrealized investment (gains) losses	(307,888)	276,272
Changes in:
Reinsurance balances, net	(518,432)	(555,356)
Reinsurance recoverable on paid and unpaid losses, net of ceded premiums payable	46,768	101,696
Funds held by reinsured companies and funds held - directly managed	115,224	62,440
Deferred acquisition costs	(105,900)	(121,359)
Net tax assets and liabilities	(55,879)	(144,342)
Unpaid losses and loss expenses including life policy benefits	(131,400)	(181,198)
Unearned premiums	550,308	590,434
Other net changes in operating assets and liabilities	(27,380)	45,951
Net cash provided by operating activities	220,887	230,758
Cash flows from investing activities
Redemptions of fixed maturities	338,238	772,227
Payments/ proceeds from trading securities [Line Items]
Sales and redemptions of short-term investments	31,405	226,390
Purchases of short-term investments	(49,706)	(105,446)
Other, net	(17,980)	(7,122)
Net cash (used in) provided by investing activities	(86,452)	489,032
Cash flows from financing activities
Dividends paid to common and preferred shareholders	(96,658)	(103,294)
Repurchase of common shares	(316,091)	(496,023)
Issuance of common shares, net of taxes paid	6,156	34,416
Net proceeds from issuance of preferred shares	0	241,265
Repurchase of preferred shares	0	(290,000)
(Distribution) sale of shares to noncontrolling interests	(14,266)	47,136
Net cash used in financing activities	(420,859)	(566,500)
Effect of foreign exchange rate changes on cash	(1,841)	(13,455)
(Decrease) increase in cash and cash equivalents	(288,265)	139,835
Cash and cash equivalents - beginning of period	1,496,485	1,121,705
Cash and cash equivalents - end of period	1,208,220	1,261,540
Supplemental cash flow information:
Taxes paid	195,261	112,671
Interest paid	24,630	24,630
Fixed maturities [Member]
Payments/ proceeds from trading securities [Line Items]
Sales of fixed maturities and sales of equities	4,276,812	3,844,517
Purchases of fixed maturities and purchases of equities	(4,683,829)	(4,198,801)
Equities [Member]
Payments/ proceeds from trading securities [Line Items]
Sales of fixed maturities and sales of equities	122,296	539,498
Purchases of fixed maturities and purchases of equities	$ (103,688)	$ (582,231)