<TABLE> <S> <C>

<PAGE>
 
<ARTICLE> 9
<MULTIPLIER> 1,000
       
<S>                             <C>                     <C>
<PERIOD-TYPE>                   9-MOS                   9-MOS
<FISCAL-YEAR-END>                          DEC-31-1998             DEC-31-1998
<PERIOD-START>                             JAN-01-1998             JAN-01-1998
<PERIOD-END>                               SEP-30-1998             SEP-30-1997
<CASH>                                         170,356                 199,129
<INT-BEARING-DEPOSITS>                          18,497                  18,465
<FED-FUNDS-SOLD>                                41,941                  16,570
<TRADING-ASSETS>                                38,362                  21,197
<INVESTMENTS-HELD-FOR-SALE>                    787,614                 611,626
<INVESTMENTS-CARRYING>                       1,059,857                 962,423
<INVESTMENTS-MARKET>                         1,064,659                 956,486
<LOANS>                                      3,057,996               2,607,352
<ALLOWANCE>                                     46,090                  39,911
<TOTAL-ASSETS>                               5,303,562               4,556,960
<DEPOSITS>                                   3,581,724               2,971,897
<SHORT-TERM>                                   482,197                 539,864
<LIABILITIES-OTHER>                             57,341                 157,401
<LONG-TERM>                                    738,589                 493,081
<PREFERRED-MANDATORY>                                0                       0
<PREFERRED>                                          0                       0
<COMMON>                                       393,275                 344,836
<OTHER-SE>                                           0                       0
<TOTAL-LIABILITIES-AND-EQUITY>               5,303,562               4,556,960
<INTEREST-LOAN>                                191,095                 168,924
<INTEREST-INVEST>                               83,725                  78,399
<INTEREST-OTHER>                                 5,387                   2,671
<INTEREST-TOTAL>                               280,207                 249,994
<INTEREST-DEPOSIT>                              97,502                  89,314
<INTEREST-EXPENSE>                             138,860                 130,205
<INTEREST-INCOME-NET>                          141,347                 119,789
<LOAN-LOSSES>                                    6,459                  11,285
<SECURITIES-GAINS>                                 158                      31
<EXPENSE-OTHER>                                104,680                  90,003
<INCOME-PRETAX>                                 93,554                  74,958
<INCOME-PRE-EXTRAORDINARY>                      93,554                  74,958
<EXTRAORDINARY>                                      0                       0
<CHANGES>                                            0                       0
<NET-INCOME>                                    62,358                  49,269
<EPS-PRIMARY>                                      .62                     .50
<EPS-DILUTED>                                      .61                     .49
<YIELD-ACTUAL>                                    4.21                    3.99
<LOANS-NON>                                        551                     111
<LOANS-PAST>                                     4,442                   4,181
<LOANS-TROUBLED>                                     0                       0
<LOANS-PROBLEM>                                    112                     319
<ALLOWANCE-OPEN>                                43,297                  35,514
<CHARGE-OFFS>                                    7,945                   9,676
<RECOVERIES>                                     3,250                   2,163
<ALLOWANCE-CLOSE>                               46,690                  39,911
<ALLOWANCE-DOMESTIC>                            46,690                  39,911
<ALLOWANCE-FOREIGN>                                  0                       0
<ALLOWANCE-UNALLOCATED>                              0                       0
        

</TABLE>