Note 12. Stock-Based Compensation Stock-Based Compensation (Tables)

12 Months Ended

Dec. 31, 2015

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

Schedule of Market Performance Unit Award Valuation Assumptions



	2015 RTSR PSU
Weighted average grant date fair value	$	41.08
Weighted average expected volatility	25.1		%
Weighted average volatility of XHB	21.1		%
Weighted average correlation coefficient	0.57
Weighted average risk-free interest rate	1.0		%
Weighted average dividend yield	—

Schedule of Nonvested Share Activity

A summary of restricted stock and restricted stock unit activity for the year ended December 31, 2015 is presented below (number of shares in millions):



	Restricted Stock		Weighted Average Grant Date Fair Value		Restricted Stock Units		Weighted Average Grant Date Fair Value
Unvested at January 1, 2015	0.09		$	27.14	0.74		$	45.83
Granted	—		—		0.63		46.40
Vested (a)	(0.09	)	27.14		(0.31	)	45.13
Forfeited	—		—		(0.04	)	46.31
Unvested at December 31, 2015	—		$	—	1.02		$	46.36

_______________


(a)	The total fair value of restricted stock and restricted stock units which vested during the year ended December 31, 2015 was $2 million and $14 million, respectively.

A summary of performance share unit activity for the year ended December 31, 2015 is presented below (number of shares in millions):



	Performance Share Units (a)		Weighted Average Grant Date Fair Value
Unvested at January 1, 2015	0.37		$	46.63
Granted	0.52		43.69
Vested (b)	(0.03	)	43.72
Unvested at December 31, 2015	0.86		$	44.97

_______________


(a)	The PSU amounts in the table are shown at the target amount of the award.


(b)	The total fair value of PSUs which vested during the year ended December 31, 2015 was approximately $1 million.

Summary of Stock Options Valuation Assumptions



	2015 Options			2014 Options			2013 Options
Weighted average grant date fair value	$	17.66		$	18.35		$	19.78
Weighted average expected volatility	36.1		%	41.5		%	43.6		%
Weighted average expected term (years)	6.25			6.25			6.25
Weighted average risk-free interest rate	1.6		%	1.4		%	1.7		%
Weighted average dividend yield	—			—			—

Summary of Stock Options Activity

A summary of stock option unit activity for the year ended December 31, 2015 is presented below (number of shares in millions):



	Options		Weighted Average Exercise Price
Outstanding at January 1, 2015	3.22		$	30.02
Granted	0.18		46.45
Exercised (a) (b)	(0.21	)	22.09
Forfeited/Expired	(0.04	)	32.48
Outstanding at December 31, 2015 (c)	3.15		$	31.42

_______________


(a)	The intrinsic value of options exercised during the year ended December 31, 2015 was $5 million.


(b)	Cash received from options exercised during the year ended December 31, 2015 was $5 million.


(c)	Options outstanding at December 31, 2015 had an intrinsic value of $31 million and have a weighted average remaining contractual life of 6.6 years.

Summary of Exercisable Stock Options Activity

The following table summarizes information regarding exercisable stock options as of December 31, 2015:



Range of Exercise Prices	Options Vested (a)	Weighted Average Exercise Price		Aggregate Intrinsic Value
$15.00 to $50.00	1.98	$	24.93	$	24.7
$50.00 and above	0.09	$	140.86	—

_______________


(a)	Exercisable stock options as of December 31, 2015 have a weighted average remaining contractual life of 7.4 years.