WARNING: THE EDGAR SYSTEM ENCOUNTERED ERROR(S) WHILE PROCESSING THIS SCHEDULE.

<TABLE> <S> <C>

<PAGE>
 
<ARTICLE> 5
       
<S>                             <C>                     <C>                     <C>
<PERIOD-TYPE>                   03-MOS                   06-MOS                   09-MOS
<FISCAL-YEAR-END>                          DEC-31-1997             DEC-31-1997             DEC-31-1997
<PERIOD-START>                             JAN-01-1997             JAN-01-1997             JAN-01-1997
<PERIOD-END>                               MAR-31-1997             JUN-30-1997             SEP-30-1997
<CASH>                                          11,493                  16,389                  19,930
<SECURITIES>                                   102,542                 104,259                 101,017
<RECEIVABLES>                                   55,244                  57,354                  55,252
<ALLOWANCES>                                     (949)                 (1,197)                 (1,209)
<INVENTORY>                                          0                       0                       0
<CURRENT-ASSETS>                               180,532                 190,805                 181,759
<PP&E>                                          47,543                  51,928                  51,863
<DEPRECIATION>                                  23,733                  26,014                  25,219
<TOTAL-ASSETS>                                 215,719                 224,205                 215,677
<CURRENT-LIABILITIES>                           45,492                  47,010                  44,727
<BONDS>                                          2,600                   2,500                   2,500
<PREFERRED-MANDATORY>                                0                       0                       0
<PREFERRED>                                          0                       0                       0
<COMMON>                                           221                     223                     257
<OTHER-SE>                                     163,465                 170,039                 163,449
<TOTAL-LIABILITY-AND-EQUITY>                   215,719                 224,205                 215,677
<SALES>                                         21,887                  27,125                  43,495
<TOTAL-REVENUES>                                59,660                 116,991                 181,589
<CGS>                                           14,242                  20,138                  31,975
<TOTAL-COSTS>                                   49,051                  85,568                 181,160
<OTHER-EXPENSES>                                 4,512                       0                       0
<LOSS-PROVISION>                                   165                     205                     592
<INTEREST-EXPENSE>                                  20                      57                      99
<INCOME-PRETAX>                                  7,292                  13,960                   4,583
<INCOME-TAX>                                     2,794                   5,587                   3,566
<INCOME-CONTINUING>                              4,498                   8,372                   1,017
<DISCONTINUED>                                       0                       0                       0
<EXTRAORDINARY>                                      0                       0                       0
<CHANGES>                                            0                       0                       0
<NET-INCOME>                                     4,498                   8,372                   1,017
<EPS-PRIMARY>                                     0.18                    0.15                  (0.29)
<EPS-DILUTED>                                     0.17                    0.15                  (0.28)
        

</TABLE>