<TABLE> <S> <C>

<PAGE>
 
<ARTICLE> 5
<LEGEND>  THE SCHEDULE CONTAINS SUMMARY FINANCIAL INFORMATION EXTRACTED FROM THE
CONDENSED CONSOLIDATED BALANCE SHEET AS OF JUNE 30, 1998 AND THE CONDENSED
CONSOLIDATED STATEMENTS OF OPERATIONS FOR THE SIX AND THREE MONTHS ENDED JUNE
30, 1998 AND FOR THE SIX AND THREE MONTHS ENDED JUNE 30, 1997 IS QUALIFIED IN
ITS ENTIRETY BY REFERENCE TO SUCH FINANCIAL STATEMENTS. (1997 PERIODS HAVE BEEN
REVISED, SEE NOTE 1 IN THE CONDENSED CONSOLIDATED FINANCIAL STATEMENTS.)
</LEGEND>
<RESTATED> 
<MULTIPLIER> 1,000
       
<S>                             <C>                     <C>                         <C>                       <C> 
<PERIOD-TYPE>                   6-MOS                   3-MOS                       6-MOS                     3-MOS                 
<FISCAL-YEAR-END>                          DEC-31-1998             DEC-31-1998                 DEC-31-1997           DEC-31-1997
<PERIOD-START>                             JAN-01-1998             APR-01-1998                 JAN-01-1997           APR-01-1997
<PERIOD-END>                               JUN-30-1998             JUN-30-1998                 JUN-30-1997           JUN-30-1997
<CASH>                                          13,938                  13,938                           0                     0
<SECURITIES>                                         0                       0                           0                     0
<RECEIVABLES>                                   85,938                  85,938                           0                     0
<ALLOWANCES>                                         0                       0                           0                     0
<INVENTORY>                                          0                       0                           0                     0
<CURRENT-ASSETS>                               178,279                 178,279                           0                     0
<PP&E>                                         124,043                 124,043                           0                     0
<DEPRECIATION>                                       0                       0                           0                     0
<TOTAL-ASSETS>                               1,078,129               1,078,129                           0                     0
<CURRENT-LIABILITIES>                           55,365                  55,365                           0                     0
<BONDS>                                        531,596                 531,596                           0                     0
<PREFERRED-MANDATORY>                                0                       0                           0                     0
<PREFERRED>                                          2                       2                           0                     0
<COMMON>                                           538                     538                           0                     0
<OTHER-SE>                                     333,815                 333,815                           0                     0
<TOTAL-LIABILITY-AND-EQUITY>                 1,078,129               1,078,129                           0                     0
<SALES>                                              0                       0                           0                     0
<TOTAL-REVENUES>                               196,965                 109,713                     143,566                81,513
<CGS>                                                0                       0                           0                     0
<TOTAL-COSTS>                                        0                       0                           0                     0
<OTHER-EXPENSES>                                83,948                  41,506                      60,596                30,517
<LOSS-PROVISION>                                     0                       0                           0                     0
<INTEREST-EXPENSE>                              19,827                   8,867                      12,485                 7,384
<INCOME-PRETAX>                                 47,326                  36,575                      38,776                27,639
<INCOME-TAX>                                    20,229                  15,313                      16,054                11,313
<INCOME-CONTINUING>                             27,097                  21,262                      22,722                16,326
<DISCONTINUED>                                       0                       0                           0                     0
<EXTRAORDINARY>                               (10,777)                   (808)                           0                     0
<CHANGES>                                            0                       0                           0                     0
<NET-INCOME>                                    16,320                  20,454                      22,722                16,326
<EPS-PRIMARY>                                      .29                     .37                         .55                   .40
<EPS-DILUTED>                                      .29                     .37                         .55                   .40 
        

</TABLE>