Unaudited Condensed Consolidated Statements Of Cash Flows - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015
CASH FLOWS PROVIDED BY OPERATING ACTIVITIES:
Net income	$ 296.1	$ 82.2
Adjustments to reconcile net income to cash provided by operating activities:
Net realized gains on sales of investments	(37.7)	(41.2)
Mark to market adjustments	(91.1)	112.4
Stock compensation expense	13.4	11.8
Undistributed income of equity method investments	22.2	19.2
Changes in:
Reserve for losses and loss expenses, net of reinsurance recoverables	138.9	188.8
Unearned premiums, net of prepaid reinsurance	45.5	113.4
Insurance balances receivable	(148.8)	(123.2)
Funds held	376.9	280.4
Reinsurance balances payable	44.1	40.4
Reinsurance recoverable on paid losses	(32.6)	(31.0)
Net deferred acquisition costs	7.5	(10.9)
Net deferred tax assets	(1.9)	(10.1)
Accounts payable and accrued liabilities	(28.2)	(39.0)
Other items, net	15.2	(1.7)
Net cash provided by operating activities	619.5	591.5
CASH FLOWS PROVIDED BY (USED IN) INVESTING ACTIVITIES:
Purchases of trading securities	(4,322.6)	(3,962.3)
Purchases of other invested assets	(58.5)	(110.9)
Sales of trading securities	4,595.8	3,888.4
Sales of other invested assets	99.2	160.3
Purchases of fixed assets	(3.1)	(23.8)
Change in restricted cash	(38.2)	(78.9)
Net cash paid for acquisitions	(1.2)	(141.5)
Net cash provided by (used in) investing activities	271.4	(268.7)
CASH FLOWS USED IN FINANCING ACTIVITIES:
Dividends paid	(68.8)	(66.8)
Proceeds from the exercise of stock options	7.7	9.2
Repayment of senior notes	(500.0)	0.0
Share repurchases	(165.7)	(246.4)
Proceeds from other long-term debt	0.0	4.0
Repayment of other long-term debt	(0.2)	(0.2)
Net cash used in financing activities	(727.0)	(300.2)
Effect of exchange rate changes on foreign currency cash	1.9	(8.1)
NET INCREASE IN CASH AND CASH EQUIVALENTS	165.8	14.5
CASH AND CASH EQUIVALENTS, BEGINNING OF PERIOD	608.0	589.3
CASH AND CASH EQUIVALENTS, END OF PERIOD	773.8	603.8
Supplemental disclosure of cash flow information:
Cash paid for income taxes	2.3	2.2
Cash paid for interest expense	$ 56.6	$ 45.8