Summary of Significant Accounting Policies - Accounts Receivable (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Accounts Receivable [Abstract]
Contract receivable retention	$ 15.9us-gaap_ContractReceivableRetainage	$ 10.4us-gaap_ContractReceivableRetainage
Retainage, long-term	$ 0.6

Amount billed to customers under long-term contracts or programs that have been withheld because of retainage provisions in a contract to be collected after the next fiscal year following the latest fiscal year.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.3(c)(4))

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

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 3

-Subparagraph c(4)

-Article 5

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 910

-SubTopic 310

-Section 50

-Paragraph 4

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=6471494&loc=d3e49370-109356

Name:	us-gaap_ContractReceivableRetainageDueAfterOneYear
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant