Amount of expense for award under share-based payment arrangement. Excludes amount capitalized.

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Weighted-average period over which cost not yet recognized is expected to be recognized for award under share-based payment arrangement, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

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Amount by which the current fair value of the underlying stock exceeds the exercise price of options outstanding.

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Number of shares issued under share-based payment arrangement.

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Percentage of vesting of award under share-based payment arrangement.

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Stock-Based Compensation - Narrative (Details) - USD ($)		12 Months Ended
	Mar. 20, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Jul. 01, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Intrinsic value of options exercised		$ 0	$ 0	$ 0
Aggregate intrinsic value of options outstanding			0	0
Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense		10,000,000	9,000,000	7,000,000
Unrecognized stock based compensation expense		$ 23,000,000
Period to be recognized		1 year 9 months 18 days
2006 Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense		$ 13,000,000	$ 11,000,000	$ 11,000,000
2006 Plan \| Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Options available for future grants (in shares)		1,416,986
LTIP \| Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period		3 years
2018 ExLTIP II \| Restricted Stock Units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	4 years
2017 ESPP \| Employee Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares authorized (in shares)					800,000
Number of shares issued (in shares)		106,881	114,385
Share-based Payment Arrangement, Tranche One [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percentage		0.33%
Share-based Payment Arrangement, Tranche Two [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percentage		0.33%
Share-based Payment Arrangement, Tranche Three [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percentage		0.33%