Equity-Based Compensation - Summary of SAR Activity (Detail) (USD $)	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares, Granted	0	0	0
Stock Appreciation Rights (SARs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares, Outstanding at beginning of year	1,402,784	1,535,804	1,287,724
Shares, Granted	195,560	326,811	431,040
Shares, Exercised	(267,077)	(376,673)	(102,972)
Shares, Forfeited	(38,738)	(80,515)	(75,978)
Shares, Expired	(387)	(2,643)	(4,010)
Shares, Outstanding at end of period	1,292,142	1,402,784	1,535,804
Shares, Exercisable at end of period	586,344	520,426	514,787
Weighted-Average Exercise Price, Outstanding at beginning of year	36.36	31.66	28.91
Weighted-Average Exercise Price, Granted	74.59	46.13	38.51
Weighted-Average Exercise Price, Exercised	34.03	25.44	23.83
Weighted-Average Exercise Price, Forfeited	50.57	37.54	34.10
Weighted-Average Exercise Price, Expired	46.07	33.70	41.57
Weighted-Average Exercise Price, Outstanding at end of year	42.20	36.36	31.66
Weighted-Average Exercise Price, Exercisable at end of year	33.03	30.51	26.52
Intrinsic value of exercised SARs	10,800,000	7,900,000	1,500,000

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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.

+ References

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-Publisher FASB

-Name Accounting Standards Codification

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-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)(1)(iii)

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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.

+ References

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Amount of accumulated difference between fair value of underlying shares on dates of exercise and exercise price on options exercised (or share units converted) into shares.

+ References

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-Publisher FASB

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- Definition

Number of options or other stock instruments for which the right to exercise has lapsed under the terms of the plan agreements.

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-Name Accounting Standards Codification

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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.

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- Definition

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

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No definition available.

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

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- Definition

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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Weighted average price at which grantees could have acquired the underlying shares with respect to stock options that were terminated.

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- Definition

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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- Definition

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

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