<TABLE> <S> <C>

<PAGE>
 
<ARTICLE> 7
<MULTIPLIER> 1,000 
       
<S>                             <C>                    <C> 
<PERIOD-TYPE>                   3-MOS                  9-MOS
<FISCAL-YEAR-END>                      SEP-30-1997            SEP-30-1997
<PERIOD-START>                         APR-01-1997            OCT-01-1996
<PERIOD-END>                           JUN-30-1997            JUN-30-1997
<DEBT-HELD-FOR-SALE>                       476,073                476,073
<DEBT-CARRYING-VALUE>                            0                      0 
<DEBT-MARKET-VALUE>                              0                      0
<EQUITIES>                                       0                      0
<MORTGAGE>                                       0                      0
<REAL-ESTATE>                                    0                      0
<TOTAL-INVEST>                             476,073                476,073
<CASH>                                      67,367                 67,367
<RECOVER-REINSURE>                               0                      0
<DEFERRED-ACQUISITION>                      12,650                 12,650
<TOTAL-ASSETS>                             701,497                701,497
<POLICY-LOSSES>                             42,672                 42,672
<UNEARNED-PREMIUMS>                         95,723                 95,723
<POLICY-OTHER>                                   0                      0
<POLICY-HOLDER-FUNDS>                            0                      0
<NOTES-PAYABLE>                                  0                      0
<COMMON>                                    15,073                 15,073
<PREFERRED-MANDATORY>                            0                      0
<PREFERRED>                                  3,000                  3,000
<OTHER-SE>                                 402,600                402,600
<TOTAL-LIABILITY-AND-EQUITY>               701,497                701,497
<PREMIUMS>                                  45,903                130,426
<INVESTMENT-INCOME>                          8,468                 24,759
<INVESTMENT-GAINS>                           (564)                  (141)
<OTHER-INCOME>                                 125                    125
<BENEFITS>                                   4,475                 22,198
<UNDERWRITING-AMORTIZATION>                  8,018                 20,917
<UNDERWRITING-OTHER>                         3,754                 13,624
<INCOME-PRETAX>                             37,685                 98,430
<INCOME-TAX>                                     0                      0
<INCOME-CONTINUING>                         37,685                 98,430
<DISCONTINUED>                                   0                      0
<EXTRAORDINARY>                                  0                      0
<CHANGES>                                        0                      0
<NET-INCOME>                                37,685                 98,430
<EPS-PRIMARY>                                 1.63                   4.10
<EPS-DILUTED>                                 1.62                   4.08
<RESERVE-OPEN>                              43,314                 49,875
<PROVISION-CURRENT>                          2,955                 10,952
<PROVISION-PRIOR>                            1,480                 11,199
<PAYMENTS-CURRENT>                             385                (2,175)
<PAYMENTS-PRIOR>                           (5,462)               (27,179)
<RESERVE-CLOSE>                             42,672                 42,672
<CUMULATIVE-DEFICIENCY>                          0                      0 
        


</TABLE>