Number of terminals.

No definition available.

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- Definition

Number of tractors in operating fleet.

+ References

No definition available.

+ Details

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Data Type:	xbrli:integerItemType
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- Definition

Date when the business acquisition agreement was executed, in CCYY-MM-DD format.

+ References

No definition available.

+ Details

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Data Type:	xbrli:dateItemType
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- Definition

Aggregate dividends declared during the period for each share of common stock outstanding.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 505
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.3-04)
-URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187085-122770

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- Definition

Date the declared dividend will be paid, in CCYY-MM-DD format.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=98513485&loc=d3e4304-108586

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Period Type:	duration

- Definition

Date the dividend to be paid was declared, in CCYY-MM-DD format.

+ References

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:dateItemType
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Period Type:	duration

- Definition

Date the holder must own the stock to be entitled to the dividend, in CCYY-MM-DD format.

+ References

No definition available.

+ Details

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- Definition

The cash outflow associated with the acquisition of business during the period. The cash portion only of the acquisition price.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 50
-Paragraph 1
-Subparagraph (b)(1)
-URI http://asc.fasb.org/extlink&oid=35744584&loc=d3e6927-128479

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-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 13
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=109223946&loc=d3e3213-108585

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The cash outflow for purchases of and capital improvements on property, plant and equipment (capital expenditures), software, and other intangible assets.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 13
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=109223946&loc=d3e3213-108585

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- Definition

Detail information of subsequent event by type. User is expected to use existing line items from elsewhere in the taxonomy as the primary line items for this disclosure, which is further associated with dimension and member elements pertaining to a subsequent event.

+ References

No definition available.

+ Details

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- Details

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Subsequent Events - Additional Information (Detail) $ / shares in Units, $ in Thousands				3 Months Ended		9 Months Ended
	Oct. 25, 2018 $ / shares	Oct. 12, 2018 USD ($) a Tractor	Jul. 26, 2018 $ / shares	Sep. 29, 2018 $ / shares	Sep. 30, 2017 $ / shares	Sep. 29, 2018 USD ($) $ / shares	Sep. 30, 2017 $ / shares
Subsequent Event [Line Items]
Payments to acquire Business						$ 100,787
Dividends payable, date declared			Jul. 26, 2018
Quarterly cash dividend declared per common stock \| $ / shares			$ 0.105	$ 0.105	$ 0.070	$ 0.315	$ 0.210
Dividends payable, recorded date			Aug. 06, 2018
Dividends payable, date to be paid			Aug. 16, 2018
Subsequent Event [Member]
Subsequent Event [Line Items]
Dividends payable, date declared	Oct. 25, 2018
Quarterly cash dividend declared per common stock \| $ / shares	$ 0.105
Dividends payable, recorded date	Nov. 05, 2018
Dividends payable, date to be paid	Nov. 15, 2018
Specialized Rail Service [Member] \| Stock Purchase Agreement [Member] \| Subsequent Event [Member]
Subsequent Event [Line Items]
Acquisition agreement date		Oct. 12, 2018
Payments to acquire Business		$ 12,300
Number of tractors in operating fleet \| Tractor		140
Number of terminals \| a		7
Payments to acquire terminal		$ 3,000