Share-based Compensation (Tables)
 9 Months Ended
Sep. 30, 2016
Share-based Compensation [Abstract]  
Summary of Restricted Stock and Performance Unit Award Activity
The following table presents restricted stock and performance unit award activity for the nine months ended September 30, 2016:
 
Restricted Stock
 
Performance Units
 
Shares
 
Weighted Average Grant- Date Fair Value
 
Shares
 
Weighted Average Grant- Date Fair Value
Outstanding at January 1, 2016
1,007,794

 
$
49.47

 
175,675

 
$
59.94

Granted
242,835

 
67.48

 
77,017

 
67.57

Vested (a)
(417,544
)
 
33.19

 
(20,604
)
 
57.58

Forfeitures
(18,233
)
 
58.72

 
—

 
—

Outstanding at September 30, 2016
814,852

 
$
62.98

 
232,088

 
$
62.68


___________
(a)
Upon vesting of the performance unit awards, PCA issued 21,111 shares of its common stock, which included 507 shares for dividends accrued during the vesting period.
Compensation Expense for Restricted Stock and Performance Units
Compensation expense for share-based awards recognized in the Consolidated Statements of Income, net of forfeitures, was as follows (dollars in millions):
 
Three Months Ended September 30
 
Nine Months Ended September 30
 
2016
 
2015
 
2016
 
2015
Restricted stock
$
3.5

 
$
3.7

 
$
12.2

 
$
11.7

Performance units
1.3

 
0.9

 
2.8

 
2.0

Total share-based compensation expense
4.8

 
4.6

 
15.0

 
13.7

Income tax benefit
(1.8
)
 
(1.8
)
 
(5.8
)
 
(5.3
)
Share-based compensation expense, net of tax benefit
$
3.0

 
$
2.8

 
$
9.2

 
$
8.4
Unrecognized Compensation For Restricted Stock and Performance Units
The unrecognized compensation expense for all share-based awards at September 30, 2016 was as follows (dollars in millions):
 
September 30, 2016
 
Unrecognized Compensation Expense
 
Remaining Weighted Average Recognition Period (in years)
Restricted stock
$
30.7

 
2.9
Performance units
9.1

 
3.0
Total unrecognized share-based compensation expense
$
39.8

 
2.9