Long-Term Incentive Plans (Stock Options Outstanding) (Detail) - $ / shares	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Long-Term Incentive Plans [Abstract]
Number of shares, outstanding at beginning of year	0	237,800	2,325,300
Stock option awards exercised	0	(200,000)	(2,050,000)
Options expired or canceled	0	(37,800)	(37,500)
Number of shares, outstanding at end of year	0	0	237,800
Number of shares, exercisable at end of year	0	0	237,800
Outstanding at beginning of year, weighted average price per share	$ 0	$ 14.6689	$ 6.3703
Exercised, weighted average price per share	0	5.05	4.4722
Expired or canceled, weighted average price per share	0	65.5624	57.51
Outstanding at end of year, weighted average price per share	0	0	14.6689
Exercisable at end of year, weighted average price per share	$ 0	$ 0	$ 14.6689

No definition available.

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

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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 price at which grantees could have acquired the underlying shares with respect to stock options of the plan that expired.

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

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