STOCK-BASED COMPENSATION (Tables)

12 Months Ended

Dec. 31, 2017

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Stock-based compensation expense

Stock-based compensation expense was as follows:

	Years ended December 31,
	2017		2016		2015
	($ in millions)
Stock-based compensation	$	18.7	$	11.2	$	11.5
Mark-to-market adjustments	4.5		3.0		(3.0		)
Total expense	$	23.2	$	14.2	$	8.5

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, 2017	5,734,740		$13.14-27.65	$	19.25	3,407,300	$	20.56
Granted	1,621,000		29.75-31.90	29.82
Exercised	(1,791,865	)	13.14-27.40	18.09
Canceled	(221,349	)	13.14-29.75	22.14
Outstanding at December 31, 2017	5,342,526		$13.14-31.90	$	22.72	2,603,962	$	21.78

Stock Options Exercisable, Exercise Price Range

The following table provides certain information with respect to stock options exercisable at December 31, 2017:

Range of Exercise Prices	Options Exercisable	Weighted-Average Exercise Price		Options Outstanding	Weighted-Average Exercise Price
Under $20.00	788,749	$	15.05	1,782,327	$	13.98
$20.00 - $25.00	855,668	22.69		855,668	22.69
Over $25.00	959,545	26.50		2,704,531	28.49
	2,603,962			5,342,526

Common shares reserved and available for grant or purchase

At December 31, 2017, 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	151,157	82,194
2003 long term incentive plan	290,389	61,205
2006 long term incentive plan	375,550	63,949
2009 long term incentive plan	2,110,063	143,310
2014 long term incentive plan	2,844,441	517,991
2016 long term incentive plan	6,000,000	4,513,000
Total under stock option plans	11,771,600	5,381,649

	Number of Shares
Stock Purchase Plans	Reserved for Issuance	Available for Grant or Purchase
1997 stock plan for non-employee directors	544,027	416,766
Employee deferral plan	45,627	45,623
Total under stock purchase plans	589,654	462,389

(1) All available to be issued as stock options, but includes a sub-limit for all types of stock awards of 2,856,933 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, 2017	542,828		$	25.84	536,575		$	16.18
Granted	154,550		30.05		154,550		30.02
Paid/Issued	(41,514	)	25.84		(40,500	)	25.57
Converted from shares to cash	82,625		17.47		(82,625	)	17.47
Canceled	(87,800	)	26.02		(87,800	)	15.16
Outstanding at December 31, 2017	650,689		$	35.62	480,200		$	19.81
Total vested at December 31, 2017	448,672		$	35.62	278,183		$	18.21

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, 2017	301,529		$	25.84
Granted	154,550		30.05
Vested	(166,262	)	35.62
Canceled	(87,800	)	26.02
Unvested at December 31, 2017	202,017		$	35.62