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: |