Loans and Allowance for Probable Loan Losses - Nonperforming Assets by Asset Class (Details) - USD ($) $ in Thousands		Mar. 31, 2018	Dec. 31, 2017
Nonperforming Assets by Asset Class [Abstract]
Nonaccrual loans	[1]	$ 34,545	$ 2,937
Accruing loans past due more than 90 days	[1]	4	1
Restructured loans	[2]	5,839	5,767
Other real estate owned		2,014	1,613
Repossessed assets		42	154
Total Nonperforming Assets		42,444	10,472
PCI loans restructured		$ 2,900	$ 2,900

[1] Excludes PCI loans measured at fair value at acquisition.

[2] Includes $2.9 million in PCI loans restructured as of March 31, 2018 and December 31, 2017.