Commitments and Contingencies (Lease Commitments) (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Commitments and Contingencies Disclosure [Abstract]
Rent expense	$ 1.5	$ 1.5	$ 1.5
2018	1.9
2019	1.6
2020	1.5
2021	1.1
2022	0.5
Total	$ 6.6

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Amount of required minimum rental payments for leases having an initial or remaining non-cancelable letter-terms in excess of one year.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 840
-SubTopic 10
-Section 55
-Paragraph 40
-Subparagraph (Note 3)
-URI http://asc.fasb.org/extlink&oid=82846649&loc=d3e38371-112697

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 840
-SubTopic 20
-Section 50
-Paragraph 2
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=77902758&loc=d3e41502-112717

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Amount of required minimum rental payments for operating leases having an initial or remaining non-cancelable lease term in excess of one year due in the fifth rolling twelve months following the latest balance sheet. For interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

+ References

No definition available.

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Amount of required minimum rental payments for operating leases having an initial or remaining non-cancelable lease term in excess of one year due in the fourth rolling twelve months following the latest balance sheet. For interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

+ References

No definition available.

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Amount of required minimum rental payments for operating leases having an initial or remaining non-cancelable lease term in excess of one year due in the third rolling twelve months following the latest balance sheet. For interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

+ References

No definition available.

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Amount of required minimum rental payments for operating leases having an initial or remaining non-cancelable lease term in excess of one year due in the second rolling twelve months following the latest balance sheet. For interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

+ References

No definition available.

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Amount of required minimum rental payments for operating leases having an initial or remaining non-cancelable lease term in excess of one year due in the next rolling twelve months following the latest balance sheet. For interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

+ References

No definition available.

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- Definition

Rental expense for the reporting period incurred under operating leases, including minimum and any contingent rent expense, net of related sublease income.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 840
-SubTopic 20
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=77902758&loc=d3e41499-112717

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