Business Combination, Indemnification Period

No definition available.

Name:	crda_BusinessCombinationIndemnificationPeriod
Namespace Prefix:	crda_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Payments To Acquire Businesses, Preliminary Gross

+ References

No definition available.

+ Details

Name:	crda_PaymentsToAcquireBusinessesPreliminaryGross
Namespace Prefix:	crda_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The aggregate expense charged against earnings to allocate the cost of intangible assets (nonphysical assets not used in production) in a systematic and rational manner to the periods expected to benefit from such assets. As a noncash expense, this element is added back to net income when calculating cash provided by or used in operations using the indirect method.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6388964&loc=d3e16225-109274

Reference 2: 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 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 30
-Section 50
-Paragraph 2
-Subparagraph (a)(2)
-URI http://asc.fasb.org/extlink&oid=66006027&loc=d3e16323-109275

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- 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_BusinessAcquisitionLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage of voting equity interests acquired at the acquisition date in the business combination.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=65885119&loc=d3e1392-128463

+ Details

Name:	us-gaap_BusinessAcquisitionPercentageOfVotingInterestsAcquired
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Amount paid or received to resolve the preacquisition contingency.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 340
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SAB Topic 2.A.6)
-URI http://asc.fasb.org/extlink&oid=27011391&loc=d3e105049-122735

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=73530397&loc=d3e4845-128472

+ Details

Name:	us-gaap_BusinessAcquisitionPreacquisitionContingencyAmountOfSettlement
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The amount of indemnification assets (amounts to be reimbursed if and when certain assumed liabilities are paid) recognized at the acquisition date of a business combination.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=73530397&loc=d3e4845-128472

+ Details

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

- Definition

This element represents the amount of any measurement period adjustment (as defined) realized during the reporting period to items of consideration transferred in connection with a business combination for which the initial accounting was incomplete.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 20
-Section 50
-Paragraph 4A
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=73530397&loc=SL65897772-128472

+ Details

Name:	us-gaap_BusinessCombinationProvisionalInformationInitialAccountingIncompleteAdjustmentConsiderationTransferred
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of intangible assets, excluding goodwill, acquired at the acquisition date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=73530397&loc=d3e4845-128472

+ Details

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

- Definition

Useful life of finite-lived intangible assets, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

+ Details

Name:	us-gaap_FiniteLivedIntangibleAssetUsefulLife
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- 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/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Investing Activities
-URI http://asc.fasb.org/extlink&oid=6516133

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 13
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=66902209&loc=d3e3213-108585

+ Details

Name:	us-gaap_PaymentsToAcquireBusinessesGross
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Details

Name:	us-gaap_BusinessAcquisitionAxis=crda_GABRobinsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis=us-gaap_CustomerRelationshipsMember
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- Details

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- Details

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- Details

Name:	us-gaap_RangeAxis=us-gaap_MaximumMember
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- Details

Name:	us-gaap_BusinessAcquisitionAxis=crda_GABRobinsAviationLimitedMember
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Business Acquisitions (Details) - USD ($) $ in Thousands			3 Months Ended	9 Months Ended	12 Months Ended
Business Acquisitions (Details) - USD ($) $ in Thousands	Dec. 15, 2015	Dec. 01, 2014	Sep. 30, 2016	Sep. 30, 2016	Dec. 31, 2015
GAB Robins
Business Acquisitions
Business acquisition, percentage of voting interests acquired		100.00%
Payments to acquire businesses, preliminary gross		$ 71,812
Business combination, provisional information, initial accounting incomplete, adjustment, consideration transferred					$ 2,182
Payments to acquire businesses, gross					$ 73,994
Business combination, indemnification assets, amount as of acquisition date		$ 6,329
Business combination, indemnification period		2 years
Business combination, preacquisition contingency, amounts released from escrow			$ 1,600	$ 1,600
Amortization of intangible assets			841	2,595
GAB Robins \| Customer relationships
Business Acquisitions
Business combination, intangible assets			$ 38,210	$ 38,210
Finite-lived intangible asset, useful life				14 years
GAB Robins \| Intangible assets not including customer relationships \| Minimum
Business Acquisitions
Finite-lived intangible asset, useful life				2 years
GAB Robins \| Intangible assets not including customer relationships \| Maximum
Business Acquisitions
Finite-lived intangible asset, useful life				5 years
GAB Robins Aviation Limited
Business Acquisitions
Business acquisition, percentage of voting interests acquired	36.00%	59.00%	95.00%	95.00%
Payments to acquire businesses, gross	$ 3,672