STOCK-BASED COMPENSATION (Tables)
 12 Months Ended
Dec. 31, 2019
Share-based Payment Arrangement [Abstract]  
Stock-based compensation expense Stock-based compensation expense was as follows:
 
Years ended December 31,
 
2019
 
2018
 
2017
 
($ in millions)
Stock-based compensation
$
9.4

 
$
19.3

 
$
19.1

Mark-to-market adjustments
(1.8
)
 
(10.7
)
 
4.5

Total expense
$
7.6

 
$
8.6

 
$
23.6
Stock Options Activity
Stock option transactions were as follows:
 
 
 
 
 
 
 
Exercisable
 
Shares
 
Option Price
 
Weighted-Average Option Price
 
Options
 
Weighted-Average Exercise Price
Outstanding at January 1, 2019
5,864,216

 
$13.14-32.94
 
$
24.40

 
3,571,732

 
$
22.27

Granted
1,578,200

 
26.26-26.26
 
26.26

 
 
 
 
Exercised
(135,731
)
 
13.14-15.68
 
14.10

 
 
 
 
Canceled
(96,134
)
 
13.14-32.94
 
28.19

 
 
 
 
Outstanding at December 31, 2019
7,210,551

 
$13.14-32.94
 
$
24.95

 
4,648,574

 
$
23.07
Stock Options Exercisable, Exercise Price Range
The following table provides certain information with respect to stock options exercisable at December 31, 2019:
Range of
Exercise Prices
 
Options Exercisable
 
Weighted-Average Exercise Price
 
Options Outstanding
 
Weighted-Average Exercise Price
Under $20.00
 
1,440,150

 
$
13.87

 
1,440,150

 
$
13.87

$20.00 - $26.00
 
1,288,236

 
23.77

 
1,288,236

 
23.77

Over $26.00
 
1,920,188

 
29.49

 
4,482,165

 
28.85

 
 
4,648,574

 
 
 
7,210,551

 
 
Common shares reserved and available for grant or purchase
At December 31, 2019, common shares reserved for issuance and available for grant or purchase under the following plans consisted of:
 
Number of Shares
Stock Option Plans
Reserved for Issuance
 
Available for Grant or Purchase(1)
2000 long term incentive plan
42,130

 
—

2003 long term incentive plan
187,184

 
—

2006 long term incentive plan
164,138

 
—

2009 long term incentive plan
1,701,404

 
—

2014 long term incentive plan
1,821,795

 
—

2016 long term incentive plan
2,285,000

 
—

2018 long term incentive plan
9,583,249

 
7,646,099

Total under stock option plans
15,784,900

 
7,646,099


 
Number of Shares
Stock Purchase Plans
Reserved for Issuance
 
Available for Grant or Purchase
1997 stock plan for non-employee directors
483,860

 
302,796



(1)
All available to be issued as stock options, but includes a sub-limit for all types of stock awards of 1,589,950 shares.
Performance Shares Transactions Performance share transactions were as follows:
 
To Settle in Cash
 
To Settle in Shares
 
Shares
 
Weighted-Average Fair Value per Share
 
Shares
 
Weighted-Average Fair Value per Share
Outstanding at January 1, 2019
670,303

 
$
19.89

 
490,700

 
$
21.58

Granted
149,950

 
26.26

 
149,950

 
26.26

Paid/Issued
(193,408
)
 
19.89

 
(128,275
)
 
13.14

Converted from shares to cash
2,296

 
29.94

 
(2,296
)
 
29.94

Canceled
(311,431
)
 
19.13

 
(206,004
)
 
19.15

Outstanding at December 31, 2019
317,710

 
$
17.18

 
304,075

 
$
28.91

Total vested at December 31, 2019
192,143

 
$
17.18

 
177,558

 
$
29.77
Summary of Unvested Performance Shares
The summary of the status of our unvested performance shares to be settled in cash were as follows:
 
Shares
 
Weighted-Average Fair Value per Share
Unvested at January 1, 2019
105,617

 
$
19.89

Granted
149,950

 
26.26

Vested
(127,776
)
 
17.18

Canceled
(2,224
)
 
24.35

Unvested at December 31, 2019
125,567

 
$
17.18