<TABLE> <S> <C>

<PAGE>
 
<ARTICLE> 7
<MULTIPLIER> 1,000
       
<S>                             <C>                     <C> 
<PERIOD-TYPE>                   3-MOS                   6-MOS
<FISCAL-YEAR-END>                        SEP-30-1998             SEP-30-1998   
<PERIOD-START>                           JAN-01-1998             OCT-01-1997
<PERIOD-END>                             MAR-31-1998             MAR-31-1998
<DEBT-HELD-FOR-SALE>                               0                       0
<DEBT-CARRYING-VALUE>                              0                       0
<DEBT-MARKET-VALUE>                                0                       0
<EQUITIES>                                         0                       0
<MORTGAGE>                                         0                       0
<REAL-ESTATE>                                      0                       0
<TOTAL-INVEST>                               508,138                 508,138
<CASH>                                        77,413                  77,413
<RECOVER-REINSURE>                                 0                       0
<DEFERRED-ACQUISITION>                        16,458                  16,458
<TOTAL-ASSETS>                               758,586                 758,586
<POLICY-LOSSES>                               51,870                  51,870
<UNEARNED-PREMIUMS>                          110,524                 110,524
<POLICY-OTHER>                                     0                       0
<POLICY-HOLDER-FUNDS>                              0                       0
<NOTES-PAYABLE>                                    0                       0
<COMMON>                                      15,165                  15,165
<PREFERRED-MANDATORY>                              0                       0
<PREFERRED>                                    3,000                   3,000
<OTHER-SE>                                   423,482                 423,482
<TOTAL-LIABILITY-AND-EQUITY>                 758,586<F1>             758,586<F1>
<PREMIUMS>                                    41,906                  79,825
<INVESTMENT-INCOME>                            8,583                  17,035
<INVESTMENT-GAINS>                             1,613                   2,017
<OTHER-INCOME>                                     0                      63
<BENEFITS>                                    19,938                  28,636
<UNDERWRITING-AMORTIZATION>                    6,200                  12,374
<UNDERWRITING-OTHER>                           3,941                   6,228
<INCOME-PRETAX>                               22,023                  51,702
<INCOME-TAX>                                       0                       0
<INCOME-CONTINUING>                           22,023                  51,702
<DISCONTINUED>                                     0                       0
<EXTRAORDINARY>                                    0                       0
<CHANGES>                                          0                       0
<NET-INCOME>                                  22,023                  51,702
<EPS-PRIMARY>                                   1.06<F2>                2.53<F2>
<EPS-DILUTED>                                   0.97<F3>                2.31<F3>
<RESERVE-OPEN>                                     0<F4>                   0<F4>
<PROVISION-CURRENT>                                0<F4>                   0<F4>
<PROVISION-PRIOR>                                  0<F4>                   0<F4>
<PAYMENTS-CURRENT>                                 0<F4>                   0<F4>
<PAYMENTS-PRIOR>                                   0<F4>                   0<F4>
<RESERVE-CLOSE>                                    0<F4>                   0<F4>
<CUMULATIVE-DEFICIENCY>                            0<F4>                   0<F4>
<FN>

<F1> Includes minority interest.

<F2> Basic EPS, following adoption of SFAS 128

<F3> Diluted EPS, following adoption of SFAS 128

<F4> Amounts for Securities Act Industry Guide 6 and Exchange Act Industry Guide
     4 disclosures are not provided because the Company's loss reserves do not
     exceed one-half of the consolidated common shareholders' equity.
</FN>
        

</TABLE>