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Fair Value Measurements, Fair Value Measured On a Nonrecurring Basis (Details) - Fair Value, Measurements, Nonrecurring [Member] - USD ($) $ in Thousands | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2018 | Sep. 30, 2017 | Sep. 30, 2018 | Sep. 30, 2017
Impaired Loans [Member] |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |
Gross charge-offs against allowance for loan losses | $ 9,086 | $ 4,397 | $ 16,279 | $ 5,058
Net losses and expenses of repossessed assets, net | 0 | 0 | 0 | 0
Real estate and other repossessed assets [Member] |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |
Gross charge-offs against allowance for loan losses | 0 | 0 | 0 | 0
Net losses and expenses of repossessed assets, net | 2,161 | 4,683 | 7,388 | 4,915
Fair Value, Inputs, Level 1 [Member] | Impaired Loans [Member] |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |
Assets, Fair Value Disclosure | 0 | 0 | 0 | 0
Fair Value, Inputs, Level 1 [Member] | Real estate and other repossessed assets [Member] |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |
Assets, Fair Value Disclosure | 0 | 0 | 0 | 0
Fair Value, Inputs, Level 2 [Member] | Impaired Loans [Member] |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |
Assets, Fair Value Disclosure | 1,065 | 423 | 1,065 | 423
Fair Value, Inputs, Level 2 [Member] | Real estate and other repossessed assets [Member] |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |
Assets, Fair Value Disclosure | 4,608 | 4,392 | 4,608 | 4,392
Fair Value, Inputs, Level 3 [Member] | Impaired Loans [Member] |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |
Assets, Fair Value Disclosure | 24,428 | 10,960 | 24,428 | 10,960
Fair Value, Inputs, Level 3 [Member] | Real estate and other repossessed assets [Member] |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |
Assets, Fair Value Disclosure | 6,545 | 6,845 | 6,545 | 6,845
Discounted Cash Flow [Member] | Management knowledge of Industry [Member] | Fair Value, Inputs, Level 3 [Member] | Impaired Loans [Member] |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |
Assets, Fair Value Disclosure | 24,428 |  | 24,428 |
Discounted Cash Flow [Member] | Recoverable oil and gas reserves, forward-looking commodity prices, and estimated operating costs [Member] | Fair Value, Inputs, Level 3 [Member] | Impaired Loans [Member] |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |
Assets, Fair Value Disclosure |  | 10,960 |  | 10,960
Discounted Cash Flow [Member] | Recoverable oil and gas reserves, forward-looking commodity prices, and estimated operating costs [Member] | Fair Value, Inputs, Level 3 [Member] | Real estate and other repossessed assets [Member] |  |  |  |
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |
Assets, Fair Value Disclosure | $ 6,545 | $ 6,845 | $ 6,545 | $ 6,845

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- Definition Amount of loans and leases that have been written off from both loan receivables and allowance reserve for credit loss. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 310 -SubTopic 10 -Section 50 -Paragraph 11B -Subparagraph (c)(3) -URI http://asc.fasb.org/extlink&oid=84173941&loc=SL6953423-111524 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -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 + Details
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- Definition Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=99377789&loc=d3e19207-110258 + Details
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