Shareholders' Equity - Additional Information (Detail) (USD $) Share data in Millions, except Per Share data, unless otherwise specified	1 Months Ended	12 Months Ended
Dec. 31, 2012	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Equity [Abstract]
Cash dividends declared per share		$ 1.72	$ 1.46	$ 1.30
Dividends payable	$ 0us-gaap_DividendsPayableCurrent	$ 37,968,000us-gaap_DividendsPayableCurrent	$ 31,740,000us-gaap_DividendsPayableCurrent	$ 0us-gaap_DividendsPayableCurrent
Dividend per share declared		$ 0.47us-gaap_DividendsPayableAmountPerShare	$ 0.39us-gaap_DividendsPayableAmountPerShare
Shares authorized under repurchase program	250,000,000
Remaining authorized repurchase amount		$ 109,000,000
Remaining number of shares authorized to be repurchase		1.1
Stock repurchased during period as percentage of shares outstanding		1.40%

Stock Repurchased During Period As Percentage Of Shares Outstanding

No definition available.

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- Definition

Aggregate dividends declared during the period for each share of common stock outstanding.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 04

-Article 3

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 505

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.3-04)

-URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187085-122770

+ Details

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- Definition

The per share amount of a dividend declared, but not paid, as of the financial reporting date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 50

-Paragraph 3

-URI http://asc.fasb.org/extlink&oid=6367179&loc=d3e4304-108586

+ Details

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- Definition

Carrying value as of the balance sheet date of dividends declared but unpaid on equity securities issued by the entity and outstanding. Used to reflect the current portion of the liabilities (due within one year or within the normal operating cycle if longer).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 20

-Article 5

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Current Liabilities

-URI http://asc.fasb.org/extlink&oid=6509677

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section 45

-Paragraph 8

-URI http://asc.fasb.org/extlink&oid=28358313&loc=d3e6935-107765

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.20)

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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- Details

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- Definition

Amount of a stock repurchase plan authorized by an entity's Board of Directors.

+ References

No definition available.

+ Details

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- Definition

Amount remaining of a stock repurchase plan authorized by an entity's Board of Directors.

+ References

No definition available.

+ Details

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- Definition

The remaining number of shares authorized to be repurchased by an entity's Board of Directors under a stock repurchase plan.

+ References

No definition available.

+ Details

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