Loans and reserve for credit losses (Allowance for Credit Losses on Financing Receivables) (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2017	Mar. 31, 2016
Allowance for Loan and Lease Losses [Roll Forward]
Allowance at the beginning of period	$ 25,290
Loan loss (provision)/ recovery	0	$ 0
Allowance at the end of period	25,357
Total reserve for credit losses	25,797	24,870
Unallocated
Allowance for Loan and Lease Losses [Roll Forward]
Allowance at the beginning of period	1,588
Allowance at the end of period	1,045
Total reserve for credit losses	1,045	3,638
Commercial real estate: \| Commercial real estate
Allowance for Loan and Lease Losses [Roll Forward]
Allowance at the beginning of period	6,321
Allowance at the end of period	6,397
Total reserve for credit losses	6,445	3,894
Construction \| Construction
Allowance for Loan and Lease Losses [Roll Forward]
Allowance at the beginning of period	2,196
Allowance at the end of period	2,333
Total reserve for credit losses	2,601	1,366
Residential real estate \| Residential real estate
Allowance for Loan and Lease Losses [Roll Forward]
Allowance at the beginning of period	3,325
Allowance at the end of period	3,409
Total reserve for credit losses	3,434	2,417
Commercial and industrial \| Commercial and industrial
Allowance for Loan and Lease Losses [Roll Forward]
Allowance at the beginning of period	10,657
Allowance at the end of period	10,979
Total reserve for credit losses	11,054	12,572
Consumer \| Consumer
Allowance for Loan and Lease Losses [Roll Forward]
Allowance at the beginning of period	1,203
Allowance at the end of period	1,194
Total reserve for credit losses	1,218	983
Loan receivables
Allowance for Loan and Lease Losses [Roll Forward]
Allowance at the beginning of period	25,290	24,415
Loan loss (provision)/ recovery	0	0
Recoveries	611	3,320
Loans charged off	(544)	(3,305)
Allowance at the end of period	25,357	24,430
Loan receivables \| Unallocated
Allowance for Loan and Lease Losses [Roll Forward]
Allowance at the beginning of period	1,588	2,476
Loan loss (provision)/ recovery	(543)	1,162
Recoveries	0	0
Loans charged off	0	0
Allowance at the end of period	1,045	3,638
Loan receivables \| Commercial real estate: \| Commercial real estate
Allowance for Loan and Lease Losses [Roll Forward]
Allowance at the beginning of period	6,321	3,934
Loan loss (provision)/ recovery	104	(2,776)
Recoveries	2	2,728
Loans charged off	(30)	(40)
Allowance at the end of period	6,397	3,846
Loan receivables \| Construction \| Construction
Allowance for Loan and Lease Losses [Roll Forward]
Allowance at the beginning of period	2,196	1,044
Loan loss (provision)/ recovery	132	16
Recoveries	5	38
Loans charged off	0	0
Allowance at the end of period	2,333	1,098
Loan receivables \| Residential real estate \| Residential real estate
Allowance for Loan and Lease Losses [Roll Forward]
Allowance at the beginning of period	3,325	2,075
Loan loss (provision)/ recovery	82	204
Recoveries	51	131
Loans charged off	(49)	(18)
Allowance at the end of period	3,409	2,392
Loan receivables \| Commercial and industrial \| Commercial and industrial
Allowance for Loan and Lease Losses [Roll Forward]
Allowance at the beginning of period	10,657	13,969
Loan loss (provision)/ recovery	47	1,129
Recoveries	401	159
Loans charged off	(126)	(2,760)
Allowance at the end of period	10,979	12,497
Loan receivables \| Consumer \| Consumer
Allowance for Loan and Lease Losses [Roll Forward]
Allowance at the beginning of period	1,203	917
Loan loss (provision)/ recovery	178	265
Recoveries	152	264
Loans charged off	(339)	(487)
Allowance at the end of period	1,194	959
Reserve for 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
Reserve for unfunded lending commitments \| Unallocated
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
Reserve for unfunded lending commitments \| Commercial real estate: \| Commercial real estate
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
Reserve for unfunded lending commitments \| Construction \| Construction
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
Reserve for unfunded lending commitments \| Residential real estate \| Residential real estate
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
Reserve for unfunded lending commitments \| Commercial and industrial \| Commercial and industrial
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
Reserve for unfunded lending commitments \| Consumer \| Consumer
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

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=66008989&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=66008989&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 10
-Section S99
-Paragraph 4
-Subparagraph (SAB Topic 6.L.1)
-URI http://asc.fasb.org/extlink&oid=27010918&loc=d3e74567-122707

Reference 5: 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

+ 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=66902209&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=66008989&loc=SL6953423-111524

+ Details

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

- Details

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

- Details

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

- Details

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

- Details

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

- Details

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

- Details

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

- Details

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

- Details

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

- Details

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

- Details

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

- Details

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

- 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: