Stock-Based Compensation Expense (Stock Options) (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract]
Outstanding, intrinsic value	$ 253
Stock option grants
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Beginning (in shares)	557,298,000	581,124,000
Granted (in shares)	347,800,000	0
Exercised (in shares)	0	0
Forfeited and canceled (in shares)	(133,984,000)	(23,826,000)
Ending (in shares)	771,114,000	557,298,000	581,124,000
Exercisable at the end of period (in shares)	271,103,000	180,424,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract]
Beginning balance (usd per share)	$ 25,460	$ 25,470
Granted (usd per share)	12.89	0
Exercise (usd per share)	0	0
Forfeited and canceled (usd per share)	24.52	25,700
Ending balance (usd per share)	20.00	25,460	$ 25,470
Exercisable at the end of period (usd per share)	$ 25.22	$ 24,970
Weighted-Average Remaining Contractual Term, outstanding	3 years 4 months 24 days	3 years 4 months 24 days	4 years 4 months 24 days

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.

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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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For presentations that combine terminations, the number of shares under options that were cancelled during the reporting period as a result of occurrence of a terminating event specified in contractual agreements pertaining to the stock option plan or that expired.

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Weighted average price of options that were either forfeited or expired.

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

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No definition available.

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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://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
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A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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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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Weighted average price at which option holders acquired shares when converting their stock options into shares.

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Weighted average per share amount at which grantees can acquire shares of common stock by exercise of options.

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No definition available.

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

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Number of share options (or share units) exercised during the current period.

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