XML 135 R119.htm IDEA: XBRL DOCUMENT v3.8.0.1

Commitments and Contingent Liabilities - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Commitments And Contingencies Liabilities [Line Items]
Rental expenses	$ 4,600,000	$ 3,800,000	$ 3,600,000
Sublease income	702,000	$ 737,000	$ 744,000
Minimum rental to be received in future on subleases	$ 1,800,000
Fixed rate loan commitments maturity year	2020
Variable rate loan commitments maturity year	2040
Maximum
Commitments And Contingencies Liabilities [Line Items]
Commitments to make loans period	90 days
Loan commitments fixed interest rate	19.50%
Loan commitments variable interest rate	9.25%
Minimum
Commitments And Contingencies Liabilities [Line Items]
Loan commitments fixed interest rate	3.05%
Loan commitments variable interest rate	2.45%

X

- Definition

Commitments and contingencies liabilities.

+ References

No definition available.

+ Details

Name:	by_CommitmentsAndContingenciesLiabilitiesLineItems
Namespace Prefix:	by_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Fixed rate loan commitment period.

+ References

No definition available.

+ Details

Name:	by_FixedRateLoanCommitmentPeriod
Namespace Prefix:	by_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Fixed rate loan commitments maturities ending year.

+ References

No definition available.

+ Details

Name:	by_FixedRateLoanCommitmentsMaturitiesEndingYear
Namespace Prefix:	by_
Data Type:	xbrli:gYearItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Loan commitments bearing fixed interest rate, percentage.

+ References

No definition available.

+ Details

Name:	by_LoanCommitmentsPercentageBearingFixedInterestRate
Namespace Prefix:	by_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

X

- Definition

Loan commitments bearing variable interest rate, percentage.

+ References

No definition available.

+ Details

Name:	by_LoanCommitmentsPercentageBearingVariableInterestRate
Namespace Prefix:	by_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

X

- Definition

Variable rate loan commitments maturities ending year.

+ References

No definition available.

+ Details

Name:	by_VariableRateLoanCommitmentsMaturitiesEndingYear
Namespace Prefix:	by_
Data Type:	xbrli:gYearItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Amount of rent expense incurred for leased assets, including but not limited to, furniture and equipment, that is not directly or indirectly associated with the manufacture, sale or creation of a product or product line.

+ References

No definition available.

+ Details

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

X

- Definition

Contractually required future rental payments receivable on noncancelable subleasing arrangements.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 840
-SubTopic 20
-Section 50
-Paragraph 2
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=77902758&loc=d3e41502-112717

+ Details

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

X

- Definition

Amount of sublease income excluding finance and operating lease expense.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 20
-Section 50
-Paragraph 4
-Subparagraph (e)
-URI http://asc.fasb.org/extlink&oid=77888426&loc=SL77918686-209980

+ Details

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

X

- Details

Name:	us-gaap_RangeAxis=us-gaap_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_RangeAxis=us-gaap_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: