Stock Compensation Plans - Performance Share Activity (Detail) (Performance Share [Member], USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013
Performance Share [Member]
Schedule Of Nonvested Restricted Stock Units Activities [Line Items]
Shares outstanding beginning balance	129
Shares vested	(64)
Shares awarded	251
Shares outstanding ending balance	316	129
Weighted average remaining term (Years) beginning balance	2 years 1 month 10 days	1 year 26 days
Aggregate intrinsic value, Beginning balance	$ 997
Shares vested	470
Shares awarded	1,945
Aggregate intrinsic value, Ending balance	$ 8,927	$ 997

The number of non-vested equity-based payment instruments, excluding stock (or unit) options, that validly exist and are outstanding as of the balance sheet date.

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)(2)(i)-(ii)

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

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- Definition

Weighted average remaining contractual term for equity-based awards excluding options, 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 50

-Paragraph 2

-Subparagraph (e)(1)

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

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Period Type:	duration

- Definition

The number of equity-based payment instruments, excluding stock (or unit) options, that vested during the reporting period.

+ 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)(2)(iii)(2)

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

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- Definition

Share Based Compensation Arrangement By Share Based payment award equity instruments other than options awarded in period.

+ References

No definition available.

+ Details

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- Definition

Share based compensation arrangement by share based payment award equity instruments other than options grants in period aggregated intrinsic value.

+ References

No definition available.

+ Details

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- Definition

Share based compensation arrangement by share based payment award equity instruments other than options nonvested aggregated intrinsic value.

+ References

No definition available.

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- Definition

Share based compensation arrangement by share based payment award equity instruments other than options vested in period aggregated intrinsic value period aggregated intrinsic value.

+ References

No definition available.

+ Details

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