<TABLE> <S> <C>

<PAGE>
 
<ARTICLE> 9
<MULTIPLIER>  1,000
       
<S>                             <C>                     <C>
<PERIOD-TYPE>                   6-MOS                   6-MOS
<FISCAL-YEAR-END>                          DEC-31-1997             DEC-31-1996
<PERIOD-START>                             JAN-01-1997             JAN-01-1996
<PERIOD-END>                               JUN-30-1997             JUN-30-1996
<CASH>                                         147,431                 151,540
<INT-BEARING-DEPOSITS>                          17,933                  17,400
<FED-FUNDS-SOLD>                                24,639                  22,092
<TRADING-ASSETS>                                34,059                  35,559
<INVESTMENTS-HELD-FOR-SALE>                    733,615                 615,890
<INVESTMENTS-CARRYING>                         882,584                 823,045
<INVESTMENTS-MARKET>                           869,030                 804,038
<LOANS>                                      2,540,652               2,133,998
<ALLOWANCE>                                     38,110                  32,475
<TOTAL-ASSETS>                               4,521,583               3,895,972
<DEPOSITS>                                   2,997,545               2,641,049
<SHORT-TERM>                                   757,331                 398,898
<LIABILITIES-OTHER>                             75,939                  60,905
<LONG-TERM>                                    357,844                 454,728
<PREFERRED-MANDATORY>                                0                       0
<PREFERRED>                                          0                       0
<COMMON>                                       332,924                 289,974
<OTHER-SE>                                           0                       0
<TOTAL-LIABILITIES-AND-EQUITY>               4,521,583               3,895,972
<INTEREST-LOAN>                                108,929                  90,142
<INTEREST-INVEST>                               52,248                  45,692
<INTEREST-OTHER>                                 1,679                   1,861
<INTEREST-TOTAL>                               162,856                 137,695
<INTEREST-DEPOSIT>                              59,180                  50,497
<INTEREST-EXPENSE>                              85,991                  71,534
<INTEREST-INCOME-NET>                           76,865                  66,161
<LOAN-LOSSES>                                    7,005                   7,295
<SECURITIES-GAINS>                                  29                   (232)
<EXPENSE-OTHER>                                 58,567                  51,777
<INCOME-PRETAX>                                 47,738                  40,906
<INCOME-PRE-EXTRAORDINARY>                      47,738                  40,906
<EXTRAORDINARY>                                      0                       0
<CHANGES>                                            0                       0
<NET-INCOME>                                    31,224                  27,039
<EPS-PRIMARY>                                      .62                     .54
<EPS-DILUTED>                                      .62                     .54
<YIELD-ACTUAL>                                    3.93                    3.97
<LOANS-NON>                                          0                       0
<LOANS-PAST>                                     4,196                   2,561
<LOANS-TROUBLED>                                     0                       0
<LOANS-PROBLEM>                                      0                     499
<ALLOWANCE-OPEN>                                35,514                  29,010
<CHARGE-OFFS>                                    6,554                   5,094
<RECOVERIES>                                     1,520                   1,667
<ALLOWANCE-CLOSE>                               38,110                  32,475
<ALLOWANCE-DOMESTIC>                            38,110                  32,475
<ALLOWANCE-FOREIGN>                                  0                       0
<ALLOWANCE-UNALLOCATED>                              0                       0
        


</TABLE>