XML 46 R31.htm IDEA: XBRL DOCUMENT
v3.8.0.1

Summary of Significant Accounting Policies (Schedule of Effects of Change in Accounting Estimate) (Details) - Change in accounting method accounted for as change in estimate [Member] - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2017 | Dec. 31, 2016
Change in Accounting Estimate [Line Items] |  |
Change in Accounting Estimate, Description |  | During fourth quarter 2016, due to the weak used truck market, we reduced the estimated life of certain trucks to more rapidly depreciate the trucks to their residual values.
Depreciation | $ 3.4 | $ 4.1

X
- Definition Describes the specific accounting estimate that was revised, including the nature of and justification for the revision. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 270 -SubTopic 10 -Section 45 -Paragraph 14 -URI http://asc.fasb.org/extlink&oid=68064558&loc=d3e777-108305 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 250 -SubTopic 10 -Section 50 -Paragraph 4 -URI http://asc.fasb.org/extlink&oid=64853466&loc=d3e22595-107794 + Details
Name: | us-gaap_ChangeInAccountingEstimateDescription
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
Name: | us-gaap_ChangeInAccountingEstimateLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition The amount of expense recognized in the current period that reflects the allocation of the cost of tangible assets over the assets' useful lives. Includes production and non-production related depreciation. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=66902209&loc=d3e3602-108585 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 360 -SubTopic 10 -Section 50 -Paragraph 1 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=6391035&loc=d3e2868-110229 + Details
Name: | us-gaap_Depreciation
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Details
Name: | us-gaap_ChangeInAccountingEstimateByTypeAxis=us-gaap_ChangeInAccountingMethodAccountedForAsChangeInEstimateMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |