Loans and Allowance for Probable Loan Losses - Nonperforming Assets by Asset Class (Details) - USD ($)		Sep. 30, 2019	Dec. 31, 2018
Nonperforming Assets by Asset Class [Abstract]
Nonaccrual loans	[1],[2]	$ 17,148,000	$ 35,770,000
Accruing loans past due more than 90 days	[2]	0	0
Restructured loans	[3]	11,683,000	5,930,000
Other real estate owned		912,000	1,206,000
Repossessed assets		4,000	0
Total nonperforming assets		29,747,000	42,906,000
Restructured nonaccrual loans		8,900,000	10,900,000
PCI loans restructured		$ 757,000	$ 3,100,000

[1] Includes $8.9 million and $10.9 million of restructured loans as of September 30, 2019 and December 31, 2018, respectively.

[2] Excludes PCI loans measured at fair value at acquisition if the timing and amount of cash flows expected to be collected from those sales can be reasonably estimated.

[3] Includes $757,000 and $3.1 million in PCI loans restructured as of September 30, 2019 and December 31, 2018, respectively.