Stock-Based Compensation - Equity Awards Outstanding and Exercisable (Detail) (USD $)	6 Months Ended	12 Months Ended
Jun. 30, 2013	Dec. 31, 2012
Options, Weighted Average Remaining Term
Options, Weighted Average Remaining Term at the end of the period	7 years 11 months 27 days	8 years 3 months 15 days
Options Outstanding
Options outstanding at beginning of period	1,383,332
Options, Granted	55,500
Options, Exercised	42,184
Options, Forfeited	10,348
Options, outstanding at end of period	1,386,300	1,383,332
Options, Weighted Average Exercise Price
Options, Weighted Average Exercise Price, at beginning of period	$ 10.06
Options, Weighted Average Exercise Price, Granted	$ 17.32
Options, Weighted Average Exercise Price, Exercised	$ 4.49
Options, Weighted Average Exercise Price, Forfeited	$ 13.12
Options, Weighted Average Exercise Price, at end of period	$ 10.49	$ 10.06
Options, Weighted Average Remaining Term at the end of the period	7 years 11 months 27 days	8 years 3 months 15 days
Restricted Stock Units, Shares
Restricted Stock Units, shares at beginning of period	883,816
Restricted Stock Units, shares, Granted	140,714
Restricted Stock Units, shares, Exercised
Restricted Stock Units, shares, Forfeited	68,000
Restricted Stock Units, shares at end of period	956,530	883,816
Restricted Stock, Weighted Average Grant Date Fair Value
Restricted Stock, Weighted Average Grant Date Fair Value at beginning of period	$ 11.31
Restricted Stock, Weighted Average Grant Date Fair Value, Granted	$ 12.62
Restricted Stock, Weighted Average Grant Date Fair Value, Exercised
Restricted Stock, Weighted Average Grant Date Fair Value, Forfeited	$ 10.65
Restricted Stock, Weighted Average Grant Date Fair Value at end of period	$ 11.55	$ 11.31
Minimum [Member]
Options, Weighted Average Exercise Price
Options, Weighted Average Exercise Price, at beginning of period	$ 2.28
Options, Weighted Average Exercise Price, Granted	$ 17.10
Options, Weighted Average Exercise Price, Exercised	$ 2.96
Options, Weighted Average Exercise Price, Forfeited	$ 6.08
Options, Weighted Average Exercise Price, at end of period	$ 2.28
Maximum [Member]
Options, Weighted Average Exercise Price
Options, Weighted Average Exercise Price, at beginning of period	$ 18.07
Options, Weighted Average Exercise Price, Granted	$ 18.59
Options, Weighted Average Exercise Price, Exercised	$ 6.08
Options, Weighted Average Exercise Price, Forfeited	$ 13.37
Options, Weighted Average Exercise Price, at end of period	$ 18.59

Weighted average fair value as of the grant date of equity-based award plans other than stock (unit) option plans that were not exercised or put into effect as a result of the occurrence of a terminating event.

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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).

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The weighted average fair value of nonvested awards on equity-based plans excluding option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, revenue or profit achievement stock award plan) for which the employer is contingently obligated to issue equity instruments or transfer assets to an employee who has not yet satisfied service or performance criteria necessary to gain title to proceeds from the sale of the award or underlying shares or units.

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- Definition

The weighted average fair value as of grant date pertaining to an equity-based award plan other than a stock (or unit) option plan for which the grantee gained the right during the reporting period, by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash in accordance with the terms of the arrangement.

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- Definition

Number of non-option equity instruments exercised by participants.

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- Definition

Number of shares under non-option equity instrument agreements that were cancelled as a result of occurrence of a terminating event.

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- Definition

Net number of non-option equity instruments granted to participants.

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- Definition

Number of equity instruments other than options outstanding, including both vested and non-vested instruments.

+ 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 (c)(1)(i)

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- Definition

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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- Definition

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

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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-Topic 718

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-Subparagraph (c)(1)(i)-(ii)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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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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- Definition

Weighted average remaining contractual term for option awards outstanding, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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- Definition

Weighted average price at which option holders acquired shares when converting their stock options into shares.

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- Definition

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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- Definition

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

+ 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 50

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-Section S99

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-Publisher FASB

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-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.28,29)

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-Publisher SEC

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-Number 210

-Section 02

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