Regulatory Matters - Additional Information (Detail) - USD ($)	6 Months Ended
	Jun. 30, 2016	Dec. 31, 2015	Dec. 31, 2014
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Capital conservation buffer phased period	4 years
Maximum capital conservation buffer percentage on risk-weighted assets , 2016	0.625%
Maximum capital conservation buffer percentage on risk-weighted assets , 2017	1.25%
Maximum capital conservation buffer percentage on risk-weighted assets , 2018	1.875%
Maximum capital conservation buffer percentage on risk-weighted assets , 2019 and thereafter	2.50%
Maximum countercyclical buffer on common equity Tier 1 capital	2.50%
Minimum asset required to be considered advanced approach banks	$ 250,000,000,000
Minimum asset required to be considered advanced approach banks	10,000,000,000
Maximum asset required to be considered small depository institution holding companies	15,000,000,000
Minimum asset required to be considered top-tier banking organizations	$ 50,000,000,000
Tri Countries Bank [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Required to be considered well capitalized, Tier 1 capital ratio	8.00%	8.00%	6.00%
Required to be considered well capitalized, Total capital ratio	10.00%	10.00%	10.00%
Required to be considered well capitalized, Tier 1 leverage ratio	5.00%	5.00%	4.00%
Basel III Phase-in Schedule [Member] | Parent [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Minimum capital level requirements, Tier 1 capital ratio	6.00%	6.00%	4.00%
Minimum capital level requirements, Total capital ratio	8.00%	8.00%	8.00%
Minimum capital level requirements, Tier 1 leverage ratio	4.00%	4.00%
Basel III Phase-in Schedule [Member] | Tri Countries Bank [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Minimum capital level requirements, Tier 1 capital ratio	6.00%	6.00%	4.00%
Minimum capital level requirements, Total capital ratio	8.00%	8.00%	8.00%
Minimum capital level requirements, Tier 1 leverage ratio	4.00%	4.00%
Basel III Fully Phased In [Member] | Parent [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Minimum capital level requirements, Tier 1 capital ratio	8.50%	8.50%
Minimum capital level requirements, Total capital ratio	10.50%	10.50%
Minimum capital level requirements, Tier 1 leverage ratio	4.00%	4.00%
Basel III Fully Phased In [Member] | Tri Countries Bank [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Minimum capital level requirements, Tier 1 capital ratio	8.50%	8.50%
Minimum capital level requirements, Total capital ratio	10.50%	10.50%
Minimum capital level requirements, Tier 1 leverage ratio	4.00%	4.00%
Common Stock [Member] | Tri Countries Bank [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Required to be considered well capitalized, Tier 1 capital ratio	6.50%	6.50%
Common Stock [Member] | Basel III Phase-in Schedule [Member] | Parent [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Minimum capital level requirements, Tier 1 capital ratio	4.50%	4.50%
Common Stock [Member] | Basel III Phase-in Schedule [Member] | Tri Countries Bank [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Minimum capital level requirements, Tier 1 capital ratio	4.50%	4.50%
Common Stock [Member] | Basel III Fully Phased In [Member] | Parent [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Minimum capital level requirements, Tier 1 capital ratio	7.00%	7.00%
Common Stock [Member] | Basel III Fully Phased In [Member] | Tri Countries Bank [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Minimum capital level requirements, Tier 1 capital ratio	7.00%	7.00%