Stock-Based Compensation - Schedule of Information Related to Outstanding SOSARS (Detail) (Stock Only Stock Appreciation Rights (SOSARs) [Member], USD $) In Thousands, except Share data, unless otherwise specified	6 Months Ended
Jun. 30, 2014	Jun. 30, 2013
Stock Only Stock Appreciation Rights (SOSARs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Beginning Balance, Outstanding	1,977,133	2,121,454
Granted	275,529	361,923
Exercised	(19,199)	(435,562)
Canceled / forfeited	(24,719)	(73,901)
Ending Balance, Outstanding	2,208,744	1,973,914
Beginning Balance, Weighted Average Exercise Price, Outstanding	$ 13.91	$ 12.93
Weighted Average Exercise Price, Granted	$ 29.89	$ 18.36
Weighted Average Exercise Price, Exercised	$ 15.57	$ 12.63
Weighted Average Exercise Price, Canceled / forfeited	$ 18.85	$ 16.25
Ending Balance, Weighted Average Exercise Price, Outstanding	$ 15.83	$ 13.87
Weighted average grant date fair value per share	$ 9.85	$ 5.64
Aggregate grant date fair value	$ 2,713	$ 2,042
Black-Scholes assumptions
Dividend yield	1.47%	2.18%
Risk free rate of return	1.73%	0.99%
Volatility	37.59%	39.62%
Expected life	6 years	6 years

Stock-Based Compensation - Schedule of Information Related to Outstanding SOSARS (Detail) (Stock Only Stock Appreciation Rights (SOSARs) [Member], USD $)
In Thousands, except Share data, unless otherwise specified

6 Months Ended

Jun. 30, 2014

Jun. 30, 2013

Stock Only Stock Appreciation Rights (SOSARs) [Member]

Share-based Compensation Arrangement by Share-based Payment Award [Line Items]

Beginning Balance, Outstanding

1,977,133

2,121,454

Granted

275,529

361,923

Exercised

(19,199)

(435,562)

Canceled / forfeited

(24,719)

(73,901)

Ending Balance, Outstanding

2,208,744

1,973,914

Beginning Balance, Weighted Average Exercise Price, Outstanding

$ 13.91

$ 12.93

Weighted Average Exercise Price, Granted

$ 29.89

$ 18.36

Weighted Average Exercise Price, Exercised

$ 15.57

$ 12.63

Weighted Average Exercise Price, Canceled / forfeited

$ 18.85

$ 16.25

Ending Balance, Weighted Average Exercise Price, Outstanding

$ 15.83

$ 13.87

Weighted average grant date fair value per share

$ 9.85

$ 5.64

Aggregate grant date fair value

$ 2,713

$ 2,042

Black-Scholes assumptions

Dividend yield

1.47%

2.18%

Risk free rate of return

1.73%

0.99%

Volatility

37.59%

39.62%

Expected life

6 years

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The estimated dividend rate (a percentage of the share price) to be paid (expected dividends) to holders of the underlying shares over the option's term.

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Expected term of share-based compensation awards, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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The risk-free interest rate assumption that is used in valuing an option on its own shares.

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Weighted average expected volatility rate of share-based compensation awards.

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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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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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