Stock-Based Compensation - Additional Information (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]
Vesting period	3 years
Number of shares available for grant	7,200,000
Stock-based compensation expense	$ 21,302,000us-gaap_ShareBasedCompensation	$ 11,982,000us-gaap_ShareBasedCompensation	$ 10,333,000us-gaap_ShareBasedCompensation
Associated tax benefit	8,400,000	4,500,000	4,000,000
Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Annual Forfeiture Rate	0.00%
Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Annual Forfeiture Rate	12.70%
Restricted Stock [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	3 years
Stock-based compensation expense	18,200,000	10,200,000	10,200,000
Fair value of awards vested	18,300,000	6,500,000	11,700,000
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value	$ 42.55	$ 38.64	$ 29.66
Unrecognized expense	39,600,000
Unrecognized expense recognition period, years	2 years 1 month 1 day
Performance Share Unit Awards [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Annual Forfeiture Rate	3.30%
Expected percentage of PSUs earned	98.00%	112.00%	98.00%
Stock-based compensation expense	3,100,000	1,800,000	400,000
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value	$ 41.71	$ 42.01	$ 26.22
Unrecognized expense	$ 9,700,000
Unrecognized expense recognition period, years	2 years 6 months 24 days
Grant date fair value amortization term	4 years	4 years	4 years 0 months 2 days
Right to received shares of common stock	1
Performance share units initial performance period, years	3 years
Number of trading days	30 days
Performance Share Unit Awards [Member] \| Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
PSU granted percentage of earnings	0.00%
Performance Share Unit Awards [Member] \| Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
PSU granted percentage of earnings	200.00%

The rate of forfeitures assumptions that is used in calculating the fair values of a share-based compensation award.

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- Definition

Number Of Trading Days Consider For Average Closing Price

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- Definition

Percentage Of Performance Share Awards Based On Shareholder Return

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No definition available.

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- Definition

Rights Received By Common Shareholder For Each Common Share Outstanding Rights

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- Definition

The initial performance period for the performance share units.

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- Definition

Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Output, Expected Percentage Earned

+ References

No definition available.

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- Definition

Unrecognized cost of unvested share-based compensation awards.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (i)

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- Definition

Weighted average period over which unrecognized compensation is expected to be recognized for equity-based compensation plans, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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- Definition

The total recognized tax benefit related to compensation cost for equity-based payment arrangements recognized in income during the period.

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-Publisher FASB

-Name Accounting Standards Codification

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-Section 50

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- Definition

The aggregate amount of noncash, equity-based employee remuneration. This may include the value of stock or unit options, amortization of restricted stock or units, and adjustment for officers' compensation. As noncash, this element is an add back when calculating net cash generated by operating activities using the indirect method.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 28

-Subparagraph (a)

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- Definition

Period which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

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-Publisher FASB

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-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (a)(1)

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- Definition

The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

+ References

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)(2)(iii)(1)

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- Definition

Fair value of share-based awards for which the grantee gained the right by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash.

+ References

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

-Publisher FASB

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- Definition

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.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section S99

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-Name Staff Accounting Bulletin (SAB)

-Number Topic 14

-Section D

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- Definition

The maximum number of shares (or other type of equity) originally approved (usually by shareholders and board of directors), net of any subsequent amendments and adjustments, for awards under the equity-based compensation plan. As stock or unit options and equity instruments other than options are awarded to participants, the shares or units remain authorized and become reserved for issuance under outstanding awards (not necessarily vested).

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-Publisher FASB

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