Benefit Plans - Summary of Stock Option and SAR Transactions (Detail) - $ / shares		12 Months Ended
Dec. 31, 2015	Dec. 31, 2015	Dec. 31, 2014
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Number of Awards Outstanding, January 1		6,908,778	6,476,391
Number of Awards, Granted	924,000	924,000	910,375
Number of Awards, Exercised		(390,856)	(392,519)
Number of Awards, Canceled		(80,564)	(85,469)
Number of Awards Outstanding, December 31	7,361,358	7,361,358	6,908,778
Awards exercisable, December 31	5,341,685	5,341,685	4,924,249
Weighted Average Exercise Price Awards outstanding, January 1		$ 39.905	$ 38.497
Weighted Average Exercise Price, Granted		38.715	43.839
Weighted Average Exercise Price, Exercised		28.586	24.670
Weighted Average Exercise Price, Canceled		45.505	45.117
Weighted Average Exercise Price Awards outstanding, December 31	$ 40.295	40.295	39.905
Weighted Average Exercise Price exercisable, December 31	$ 39.851	$ 39.851	$ 38.742

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

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

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

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

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