Represents the expense recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

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Period which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Expected term of share-based compensation awards, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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The estimated measure of the percentage by which a share price is expected to fluctuate during a period. Volatility also may be defined as a probability-weighted measure of the dispersion of returns about the mean. The volatility of a share price is the standard deviation of the continuously compounded rates of return on the share over a specified period. That is the same as the standard deviation of the differences in the natural logarithms of the stock prices plus dividends, if any, over the period.

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The risk-free interest rate assumption that is used in valuing an option on its own shares.

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Net number of share options (or share units) granted during the period.

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The weighted average grant-date fair value of options granted during the reporting period as calculated by applying the disclosed option pricing methodology.

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Share-Based Plans - Employee Stock Purchase Plans (Details) (Employee stock purchase plans [Member], USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock compensation expense (less than $1 million in all years)	$ 1	$ 1	$ 1
ShareMatch [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period	3 years
Sharesave (1 year Vesting Period) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period	1 year
Total options granted (shares)			153,000
Fair value per option granted (usd per share)			$ 1.35
Risk free interest rate			0.23%
Expected life (years)			1 year
Expected volatility			25.00%
Sharesave (3 year Vesting Period) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period	3 years
Total options granted (shares)			430,000
Fair value per option granted (usd per share)			$ 1.63
Risk free interest rate			0.45%
Expected life (years)			3 years
Expected volatility			25.00%
Sharesave (5 year Vesting Period) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period	5 years
Total options granted (shares)			107,000
Fair value per option granted (usd per share)			$ 1.61
Risk free interest rate			0.92%
Expected life (years)			5 years
Expected volatility			25.00%