STOCK-BASED COMPENSATION (Tables)

12 Months Ended

Dec. 31, 2021

Share-based Payment Arrangement [Abstract]

Stock-based compensation expense

Stock-based compensation expense was as follows:

	Years ended December 31,
	2021		2020		2019
	($ in millions)
Stock-based compensation	$	28.4	$	17.5	$	9.4
Mark-to-market adjustments	24.7		4.8		(1.8)
Total expense	$	53.1	$	22.3	$	7.6

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, 2021	9,127,375	$13.14-32.94	$	23.06	5,671,371	$	24.57
Granted	1,154,700	28.99-58.59	30.63
Exercised	(3,378,783)	13.14-32.94	21.42
Canceled	(923,056)	13.14-32.94	20.28
Outstanding at December 31, 2021	5,980,236	13.14-58.59	$	25.88	3,736,639	$	26.60

Stock Options Exercisable, Exercise Price Range

The following table provides certain information with respect to stock options exercisable at December 31, 2021:

Range of Exercise Prices	Options Exercisable	Weighted-Average Exercise Price		Options Outstanding	Weighted-Average Exercise Price
Under $22.00	665,236	$	15.23	1,598,246	$	16.46
$22.00 - $28.00	1,353,803	26.54		1,600,790	26.49
Over $28.00	1,717,600	31.06		2,781,200	30.95
	3,736,639			5,980,236

Common shares reserved and available for grant or purchase

At December 31, 2021, 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	13,000	—
2003 long term incentive plan	74,366	—
2006 long term incentive plan	44,362	—
2009 long term incentive plan	237,117	—
2014 long term incentive plan	750,556	—
2016 long term incentive plan	1,549,833	—
2018 long term incentive plan	9,389,001	4,790,339
2021 long term incentive plan	2,750,000	2,750,000
Total under stock option plans	14,808,235	7,540,339

	Number of Shares
Stock Purchase Plans	Reserved for Issuance	Available for Grant or Purchase
1997 stock plan for non-employee directors	387,368	144,143

(1)All available to be issued as stock options, but includes a sub-limit for all types of stock awards of 2,952,130 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, 2021	393,205	$	24.84	345,430	$	21.37
Granted	399,669	24.25		364,287	24.15
Paid/Issued	(25,605)	24.84		(19,267)	32.94
Converted from shares to cash	135,237	21.45		(135,237)	21.45
Canceled	(119,232)	26.69		(118,456)	19.18
Outstanding at December 31, 2021	783,274	$	57.57	436,757	$	23.75
Total vested at December 31, 2021	592,914	$	57.57	259,010	$	22.81

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, 2021	176,250	$	24.84
Granted	399,669	24.25
Vested	(266,327)	57.57
Canceled	(119,232)	26.69
Unvested at December 31, 2021	190,360	$	57.57