v3.8.0.1
Consolidated Statements of Cash Flows - USD ($)
$ in Millions
 3 Months Ended
Mar. 31, 2018
Mar. 31, 2017
Statement of Cash Flows [Abstract]    
Net income $ 729.8 $ 430.3
Adjustments to reconcile net income to net cash provided by operating activities:    
Depreciation 40.9 41.0
Amortization of intangible assets 18.0 15.5
Net amortization of fixed-income securities 15.0 22.1
Amortization of equity-based compensation 17.4 30.9
Net realized (gains) losses on securities 48.2 (51.9)
Net (gains) losses on disposition of property and equipment 1.2 1.3
Other gains (losses) 0.0 0.2
Changes in:    
Premiums receivable (621.3) (341.4)
Reinsurance recoverables 34.3 (54.2)
Prepaid reinsurance premiums (139.5) (12.2)
Deferred acquisition costs (61.8) (28.3)
Income taxes 181.1 212.7
Unearned premiums 934.3 476.3
Loss and loss adjustment expense reserves 242.1 260.8
Accounts payable, accrued expenses, and other liabilities 283.2 137.4
Other, net 24.2 (35.7)
Net cash provided by operating activities 1,747.1 1,104.4
Purchases:    
Fixed maturities (5,563.0) (3,203.9)
Equity securities (39.9) (52.5)
Sales:    
Fixed maturities 1,692.4 1,014.1
Equity securities 428.0 86.5
Maturities, paydowns, calls, and other:    
Fixed maturities 1,422.6 1,006.5
Equity securities 0.0 26.6
Net sales (purchases) of short-term investments (175.8) 536.8
Net unsettled security transactions 89.4 83.2
Collateral on derivative instruments 0.0 (136.1)
Purchases of property and equipment (35.8) (35.0)
Sales of property and equipment 1.5 11.2
Net cash used in investing activities (2,180.6) (662.6)
Cash Flows From Financing Activities    
Proceeds from exercise of equity options 0.6 0.5
Net proceeds from issuance of Serial Preferred Shares, Series B 493.9 0.0
Net proceeds from debt issuance 589.5 0.0
Payments of debt (37.1) (6.2)
Redemption/reacquisition of subordinated debt 0.0 (30.7)
Dividends paid to common shareholders (654.9) (395.4)
Acquisition of treasury shares for restricted stock tax liabilities (36.8) (21.4)
Acquisition of treasury shares acquired in open market (0.4) 0.0
Net cash provided by (used in) financing activities 354.8 (453.2)
Decrease in cash, cash equivalents, and restricted cash (78.7) (11.4)
Cash, cash equivalents, and restricted cash - January 1 275.3 226.4
Cash, cash equivalents, and restricted cash - March 31 $ 196.6 $ 215.0