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Stock-Based Compensation
 6 Months Ended
Jun. 30, 2024
Share-Based Payment Arrangement [Abstract]  
Stock-Based Compensation Stock-Based Compensation
Stock-based compensation cost by award type follows:
(in millions)Three Months Ended
June 30,		Six Months Ended
June 30,
2024202320242023
Stock option awards$3.5 $3.7 $7.3 $7.5 
Performance share awards2.3 2.4 4.7 4.6 
Restricted stock awards2.1 1.7 5.6 4.7 
Total stock-based compensation cost incurred7.9 7.8 17.6 16.8 
Capitalized cost during the period(0.9)(1.2)(1.8)(2.4)
Amortization of capitalized cost during the period0.9 1.2 1.9 2.5 
Total stock-based compensation expense
$7.9 $7.8 $17.7 $16.9