Regulatory Capital - Capital Ratio Requirements under Prompt Corrective Action or Other Regulatory Requirements (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Dec. 31, 2018
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Capital conservation buffer	2.50%
Parent Company [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Leverage Ratio	10.60%	10.50%
Common equity risk-based ratio	12.80%	12.90%
Risk-based capital Ratio	12.80%	12.90%
Total risk-based capital Ratio	13.70%	13.80%
Leverage Amount	$ 595,782	$ 580,504
Common equity risk-based amount	595,782	580,504
Risk-based capital amount	595,782	580,504
Total risk-based capital Amount	$ 636,902	$ 620,275
Required to be considered adequately capitalized Ratio, leverage ratio	4.00%	4.00%
Required to be considered adequately capitalized Ratio, risk-based common equity capital ratio	7.00%	7.00%
Required to be considered adequately capitalized Ratio, risk-based capital ratio	8.50%	8.50%
Required to be considered adequately capitalized Ratio, Total risk-based capital ratio	10.50%	10.50%
Required to be considered adequately capitalized leverage Amount	$ 224,123	$ 220,988
Required to be considered adequately capitalized common equity capital amount	392,215	386,728
Required to be considered adequately capitalized risk-based capital Amount	394,452	382,306
Required to be considered adequately capitalized Total risk-based capital Amount	$ 487,264	$ 472,261
NBH Bank [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Leverage Ratio	8.90%	9.00%
Common equity risk-based ratio	10.80%	11.10%
Risk-based capital Ratio	10.80%	11.10%
Total risk-based capital Ratio	11.70%	12.00%
Leverage Amount	$ 499,314	$ 498,283
Common equity risk-based amount	499,314	498,283
Risk-based capital amount	499,314	498,283
Total risk-based capital Amount	$ 540,434	$ 538,054
Required to be considered well capitalized Ratio, leverage ratio	5.00%	5.00%
Required to be considered adequately capitalized Ratio, risk-based common equity capital ratio	6.50%	6.50%
Required to be considered well capitalized Ratio, risk-based capital ratio	8.00%	8.00%
Required to be considered well capitalized Ratio, Total risk-based capital ratio	10.00%	10.00%
Required to be considered well capitalized leverage Amount	$ 279,602	$ 275,703
Required to be considered well capitalized common equity capital amount	363,483	358,414
Required to be considered well capitalized risk-based capital Amount	370,298	358,938
Required to be considered well capitalized Total risk-based capital Amount	$ 462,872	$ 448,672
Required to be considered adequately capitalized Ratio, leverage ratio	4.00%	4.00%
Required to be considered adequately capitalized Ratio, risk-based common equity capital ratio	7.00%	7.00%
Required to be considered adequately capitalized Ratio, risk-based capital ratio	8.50%	8.50%
Required to be considered adequately capitalized Ratio, Total risk-based capital ratio	10.50%	10.50%
Required to be considered adequately capitalized leverage Amount	$ 223,682	$ 220,563
Required to be considered adequately capitalized common equity capital amount	391,443	385,984
Required to be considered adequately capitalized risk-based capital Amount	393,441	381,372
Required to be considered adequately capitalized Total risk-based capital Amount	$ 486,016	$ 471,106