STOCK-BASED COMPENSATION (Tables)

3 Months Ended

Mar. 31, 2016

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

Stock-based compensation expense

Stock-based compensation expense was as follows:

		Three Months Ended March 31,
		2016		2015
	($ in millions)
Stock-based compensation		$	4.4	$	2.5
Mark-to-market adjustments		0.4		5.2
Total expense		$	4.8	$	7.7

Schedule of fair value of stock options granted

The fair value of each stock option granted, which typically vests ratably over three years, but not less than one year, was estimated on the date of grant, using the Black-Scholes option-pricing model with the following weighted-average assumptions:

Grant date	2016			2015
Dividend yield	6.09		%	2.92		%
Risk-free interest rate	1.35		%	1.69		%
Expected volatility	32		%	34		%
Expected life (years)	6.0			6.0
Weighted average grant fair value (per option)	$	1.90		$	6.80
Weighted average exercise price	$	13.14		$	27.40
Shares granted	1,670,400			776,750