Unaudited Condensed Consolidated Statements Of Cash Flows - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
CASH FLOWS PROVIDED BY OPERATING ACTIVITIES:
Net income	$ 80.3	$ 74.1
Adjustments to reconcile net income to cash provided by operating activities:
Net realized losses (gains) on sales of investments	13.1	(12.0)
Mark to market adjustments	(52.8)	(27.1)
Stock compensation expense	5.5	3.9
Undistributed income of equity method investments	1.4	9.2
Changes in:
Reserve for losses and loss expenses, net of reinsurance recoverables	22.9	86.9
Unearned premiums, net of prepaid reinsurance	132.7	125.5
Insurance balances receivable	(78.3)	(139.5)
Reinsurance recoverable on paid losses	(15.5)	13.8
Funds held	169.7	287.7
Reinsurance balances payable	(20.4)	7.3
Net deferred acquisition costs	(27.8)	(21.7)
Net deferred tax assets	3.9	(0.6)
Accounts payable and accrued liabilities	(45.5)	(50.1)
Other items, net	6.2	(9.9)
Net cash provided by operating activities	195.4	347.5
CASH FLOWS PROVIDED BY (USED IN) INVESTING ACTIVITIES:
Purchases of trading securities	(779.8)	(1,530.0)
Purchases of other invested assets	(11.4)	(8.1)
Sales of trading securities	1,141.9	1,414.6
Sales of other invested assets	0.5	38.7
Purchases of fixed assets	(1.0)	(0.6)
Change in restricted cash	15.9	(26.8)
Net cash provided by (used in) investing activities	366.1	(112.2)
CASH FLOWS USED IN FINANCING ACTIVITIES:
Dividends paid	0.0	(23.4)
Proceeds from the exercise of stock options	1.4	0.4
Repayment of other long-term debt	(0.1)	(0.1)
Share repurchases	0.0	(50.0)
Net cash used in financing activities	1.3	(73.1)
Effect of exchange rate changes on foreign currency cash	1.2	1.8
NET INCREASE IN CASH AND CASH EQUIVALENTS	564.0	164.0
CASH AND CASH EQUIVALENTS, BEGINNING OF PERIOD	720.9	608.0
CASH AND CASH EQUIVALENTS, END OF PERIOD	1,284.9	772.0
Supplemental disclosure of cash flow information:
Cash paid for income taxes	0.2	1.0
Cash paid for interest expense	$ 0.0	$ 18.8