Loans and reserve for credit losses (Allowance for Credit Losses on Financing Receivables) (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2016	Mar. 31, 2015
Allowance for Loan and Lease Losses [Roll Forward]
Allowance at the beginning of period	$ 24,415
Loan loss provision (recovery)	0	$ (2,000)
Allowance at the end of period	24,430
Total reserve for credit losses	24,870	23,684
Loan Receivables
Allowance for Loan and Lease Losses [Roll Forward]
Allowance at the beginning of period	24,415	22,053
Loan loss provision (recovery)	0	(2,000)
Recoveries	3,320	4,140
Loans charged off	(3,305)	(949)
Allowance at the end of period	24,430	23,244
Unfunded Lending Commitments
Allowance for Loan and Lease Losses [Roll Forward]
Allowance at the beginning of period	440	440
Loan loss provision (recovery)	0	0
Allowance at the end of period	440	440
Commercial real estate
Allowance for Loan and Lease Losses [Roll Forward]
Allowance at the beginning of period	3,934
Allowance at the end of period	3,846
Total reserve for credit losses	3,894	4,829
Commercial real estate \| Loan Receivables
Allowance for Loan and Lease Losses [Roll Forward]
Allowance at the beginning of period	3,934	5,614
Loan loss provision (recovery)	(2,776)	(3,947)
Recoveries	2,728	3,390
Loans charged off	(40)	(276)
Allowance at the end of period	3,846	4,781
Commercial real estate \| Unfunded Lending Commitments
Allowance for Loan and Lease Losses [Roll Forward]
Allowance at the beginning of period	48	48
Loan loss provision (recovery)	0	0
Allowance at the end of period	48	48
Construction
Allowance for Loan and Lease Losses [Roll Forward]
Allowance at the beginning of period	1,044
Allowance at the end of period	1,098
Total reserve for credit losses	1,366	1,523
Construction \| Loan Receivables
Allowance for Loan and Lease Losses [Roll Forward]
Allowance at the beginning of period	1,044	1,133
Loan loss provision (recovery)	16	23
Recoveries	38	99
Loans charged off	0	0
Allowance at the end of period	1,098	1,255
Construction \| Unfunded Lending Commitments
Allowance for Loan and Lease Losses [Roll Forward]
Allowance at the beginning of period	268	268
Loan loss provision (recovery)	0	0
Allowance at the end of period	268	268
Residential real estate
Allowance for Loan and Lease Losses [Roll Forward]
Allowance at the beginning of period	2,075
Allowance at the end of period	2,392
Total reserve for credit losses	2,417	2,537
Residential real estate \| Loan Receivables
Allowance for Loan and Lease Losses [Roll Forward]
Allowance at the beginning of period	2,075	2,121
Loan loss provision (recovery)	204	276
Recoveries	131	325
Loans charged off	(18)	(210)
Allowance at the end of period	2,392	2,512
Residential real estate \| Unfunded Lending Commitments
Allowance for Loan and Lease Losses [Roll Forward]
Allowance at the beginning of period	25	25
Loan loss provision (recovery)	0	0
Allowance at the end of period	25	25
Commercial and industrial
Allowance for Loan and Lease Losses [Roll Forward]
Allowance at the beginning of period	13,969
Allowance at the end of period	12,497
Total reserve for credit losses	12,572	11,434
Commercial and industrial \| Loan Receivables
Allowance for Loan and Lease Losses [Roll Forward]
Allowance at the beginning of period	13,969	6,844
Loan loss provision (recovery)	1,129	4,436
Recoveries	159	211
Loans charged off	(2,760)	(132)
Allowance at the end of period	12,497	11,359
Commercial and industrial \| Unfunded Lending Commitments
Allowance for Loan and Lease Losses [Roll Forward]
Allowance at the beginning of period	75	75
Loan loss provision (recovery)	0	0
Allowance at the end of period	75	75
Consumer
Allowance for Loan and Lease Losses [Roll Forward]
Allowance at the beginning of period	917
Allowance at the end of period	959
Total reserve for credit losses	983	1,002
Consumer \| Loan Receivables
Allowance for Loan and Lease Losses [Roll Forward]
Allowance at the beginning of period	917	1,047
Loan loss provision (recovery)	265	147
Recoveries	264	115
Loans charged off	(487)	(331)
Allowance at the end of period	959	978
Consumer \| Unfunded Lending Commitments
Allowance for Loan and Lease Losses [Roll Forward]
Allowance at the beginning of period	24	24
Loan loss provision (recovery)	0	0
Allowance at the end of period	24	24
Unallocated
Allowance for Loan and Lease Losses [Roll Forward]
Allowance at the beginning of period	2,476
Allowance at the end of period	3,638
Total reserve for credit losses	3,638	2,359
Unallocated \| Loan Receivables
Allowance for Loan and Lease Losses [Roll Forward]
Allowance at the beginning of period	2,476	5,294
Loan loss provision (recovery)	1,162	(2,935)
Recoveries	0	0
Loans charged off	0	0
Allowance at the end of period	3,638	2,359
Unallocated \| Unfunded Lending Commitments
Allowance for Loan and Lease Losses [Roll Forward]
Allowance at the beginning of period	0	0
Loan loss provision (recovery)	0	0
Allowance at the end of period	$ 0	$ 0

Amount of recovery of loans and lease receivables which had previously been fully or partially written-off as bad debts.

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

- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

+ References

No definition available.

+ Details

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

- Definition

Amount of loans and leases that have been written off from both loan receivables and allowance reserve for credit loss.

+ References

+ Details

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

- Definition

A valuation allowance for financing receivables that are expected to be uncollectible.

+ References

+ Details

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

- Definition

Amount of allowance to cover probable credit losses on loans and leases. Includes carryover of or adjustments to the allowance for loan losses in connection with business combinations. Excludes allowance for loans and leases covered under loss sharing agreements.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11B
-Subparagraph (g)
-URI http://asc.fasb.org/extlink&oid=35738203&loc=SL6953423-111524

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11B
-Subparagraph (c)(1)
-URI http://asc.fasb.org/extlink&oid=35738203&loc=SL6953423-111524

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.7(d))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 30
-Section 50
-Paragraph 2
-Subparagraph (b)(1)(ii)
-URI http://asc.fasb.org/extlink&oid=6379141&loc=d3e15032-111544

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 03
-Paragraph 7
-Subparagraph d
-Article 9

Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Staff Accounting Bulletin (SAB)
-Number Topic 6
-Section L
-Subsection 1

+ Details

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

- Definition

Amount of expense related to estimated loss from loan and lease transactions.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 225
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-04.11)
-URI http://asc.fasb.org/extlink&oid=6879574&loc=d3e536633-122882

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11B
-Subparagraph (c)(2)
-URI http://asc.fasb.org/extlink&oid=35738203&loc=SL6953423-111524

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 04
-Paragraph 11
-Article 9

+ Details

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

- Details

Name:	us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis=us-gaap_LoansReceivableMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_AccountsNotesLoansAndFinancingReceivableByReceivableTypeAxis=cacb_UnfundedLendingCommitmentsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=us-gaap_CommercialRealEstatePortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=cacb_ConstructionPortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=us-gaap_ResidentialPortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=us-gaap_CommercialPortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=us-gaap_ConsumerPortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=us-gaap_UnallocatedFinancingReceivablesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: