The number of shares into which fully or partially vested stock options outstanding as of the balance sheet date can be currently converted under the option plan.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(1)(iii)
-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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The weighted-average price as of the balance sheet date at which grantees can acquire the shares reserved for issuance on vested portions of options outstanding and currently exercisable under the stock option plan.

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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 options outstanding, including both vested and non-vested options.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
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-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
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-Section 50
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-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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Weighted average price at which grantees can acquire the shares reserved for issuance under the stock option plan.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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The floor of a customized range of exercise prices for purposes of disclosing shares potentially issuable under outstanding stock option awards on all stock option plans and other required information pertaining to awards in the customized range.

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The ceiling of a customized range of exercise prices for purposes of disclosing shares potentially issuable under outstanding stock option awards on all stock option plans and other required information pertaining to awards in the customized range.

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Amount of difference between fair value of the underlying shares reserved for issuance and exercise price of vested portions of options outstanding and currently exercisable.

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Weighted average remaining contractual term for option awards outstanding, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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Long-Term Incentive Plans (Outstanding And Exercisable Stock Options) (Detail) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Number of Options, Outstanding	2,325,300	2,548,000	3,715,406	5,963,268
Number of Options, Exercisable	2,325,300	1,798,000	1,752,311
Weighted Average Remaining Contractual Life in Years, Stock Options Outstanding	8 months 15 days
Weighted Average Exercise Price, Stock Options Outstanding	$ 6.3703	$ 10.9888	$ 20.6883	$ 19.0485
Weighted Average Exercise Price, Stock Options Exercisable	$ 6.3703	$ 13.466	$ 38.512
Aggregate Intrinsic Value, Stock Options Outstanding	$ 4
Aggregate Intrinsic Value, Stock Options Exercisable	$ 4
$4.02-$57.71 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Average Exercise Price, Minimum	$ 4.02
Range of Average Exercise Price, Maximum	$ 57.71
Number of Options, Outstanding	2,287,500
Number of Options, Exercisable	2,287,500
Weighted Average Remaining Contractual Life in Years, Stock Options Outstanding	8 months 12 days
Weighted Average Exercise Price, Stock Options Outstanding	$ 5.3922
Weighted Average Exercise Price, Stock Options Exercisable	$ 5.3922
Aggregate Intrinsic Value, Stock Options Outstanding	$ 4
Aggregate Intrinsic Value, Stock Options Exercisable	$ 4
$58.84-$70.86 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Range of Average Exercise Price, Minimum	$ 58.84
Range of Average Exercise Price, Maximum	$ 70.86
Number of Options, Outstanding	37,800
Number of Options, Exercisable	37,800
Weighted Average Remaining Contractual Life in Years, Stock Options Outstanding	1 year 4 months 2 days
Weighted Average Exercise Price, Stock Options Outstanding	$ 65.5624
Weighted Average Exercise Price, Stock Options Exercisable	$ 65.5624
Options Exercisable [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Weighted Average Remaining Contractual Life in Years, Stock Options Outstanding	8 months 15 days
Options Exercisable [Member] \| $4.02-$57.71 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Weighted Average Remaining Contractual Life in Years, Stock Options Outstanding	8 months 12 days
Options Exercisable [Member] \| $58.84-$70.86 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Line Items]
Weighted Average Remaining Contractual Life in Years, Stock Options Outstanding	1 year 4 months 2 days