Fair Value Measurements Fair Value Measurement, Measured On Non-Recurring Basis, Signfiicant Unobservable Inputs, Quantitative Information (Details) - Fair Value, Measurements, Nonrecurring [Member] - Fair Value, Inputs, Level 3 [Member] - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2018	Mar. 31, 2017
Impaired Loans [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Carrying Value		$ 410	$ 1,614
Fair Value Measurements, Valuation Techniques		Discounted cash flows	Discounted cash flows
Fair Value Measurements, Significant Unobservable Input		Recoverable oil and gas reserves, forward-looking commodity prices, estimated operating costs	Recoverable oil and gas reserves, forward-looking commodity prices, estimated operating costs
Fair Value of Impaired Loans as a Percentage of Unpaid Principal Balance [Abstract]
Fair Value Measurements, Fair Value of Impaired Loans as a Percentage of Unpaid Principal Balance, Minimum	[1]	45.00%	76.00%
Fair Value Measurements, Fair Value of Impaired Loans as a Percentage of Unpaid Principal Balance, Maximum	[1]	45.00%	81.00%
Fair Value of Impaired Loans as a Percentage of Unpaid Principal Balance, Weighted Average	[1]	45.00%	77.00%
Real estate and other repossessed assets [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Carrying Value		$ 7,094	$ 418
Fair Value Measurements, Valuation Techniques		Discounted cash flows	Appraised value, as adjusted
Fair Value Measurements, Significant Unobservable Input		Recoverable oil and gas reserves, forward-looking commodity prices, estimated operating costs	Marketability adjustments off appraised value2	[2]
Fair Value of Real Estate and Other Repossessed Assets as a Percentage of Appraised Value [Abstract]
Fair Value Measurement, Percentage of Appraised Value. Minimum			65.00%
Fair Value Measurement, Percentage of Appraised Value, Maximum			86.00%
Fair Value Measurement, Percentage of Appraised Value, Weighted Average			78.00%

[1] Represents fair value as a percentage of the unpaid principal balance.

[2] Marketability adjustments include consideration of estimated costs to sell which is approximately 10% of the fair value.