Cost of Contracts, net (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Cost of Contracts, net
Cost of contracts	$ 28,276us-gaap_OtherDeferredCostsGross	$ 25,607us-gaap_OtherDeferredCostsGross
Accumulated amortization	(17,795)	(14,845)
Cost of contracts, net	10,481us-gaap_OtherDeferredCostsNet	10,762us-gaap_OtherDeferredCostsNet
Expected future amortization of cost of contracts
2015	2,478
2016	2,329
2017	2,126
2018	1,750
2019	1,108
2020 and Thereafter	690
Cost of contracts, net	10,481us-gaap_OtherDeferredCostsNet	10,762us-gaap_OtherDeferredCostsNet
Amortization expense, cost of contracts	$ 3,205	$ 2,788	$ 3,142
Weighted average useful life	9 years 6 months	9 years 7 months 6 days	9 years 6 months

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Represents the amount of amortization expense expected to be recognized after the fifth fiscal year following the latest fiscal year for other deferred costs.

+ References

No definition available.

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Represents the amount of amortization expense expected to be recognized during the next fiscal year following the latest fiscal year for other deferred costs.

+ References

No definition available.

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Represents the amount of amortization expense expected to be recognized during the fifth fiscal year following the latest fiscal year for other deferred costs.

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No definition available.

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Represents the amount of amortization expense expected to be recognized during the fourth fiscal year following the latest fiscal year for other deferred costs.

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No definition available.

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Represents the amount of amortization expense expected to be recognized during the third fiscal year following the latest fiscal year for other deferred costs.

+ References

No definition available.

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Represents the amount of amortization expense expected to be recognized during the second fiscal year following the latest fiscal year for other deferred costs.

+ References

No definition available.

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- Definition

Useful life of other deferred costs, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

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Accumulated amortization of other deferred costs capitalized at the end of the reporting period. Does not include deferred finance costs, deferred acquisition costs of insurance companies, or deferred leasing costs for real estate operations.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

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-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 17

-Article 5

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Amount of amortization of other deferred costs recognized in the income statement.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

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-Section S99

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-Subparagraph (SX 210.5-03.3)

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Gross amount of other deferred costs capitalized at the end of the reporting period. Does not include deferred finance costs or deferred acquisition costs of insurance companies.

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Net amount of other deferred costs capitalized at the end of the reporting period. Does not include deferred finance costs or deferred acquisition costs of insurance companies.

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