Capital Stock (Details) - USD ($) $ in Millions		1 Months Ended	3 Months Ended		6 Months Ended
	Apr. 08, 2019	Jun. 30, 2019	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Jun. 11, 2019	Dec. 31, 2018
Class of Stock [Line Items]
Stock repurchased and retired (in shares)			607	896	39,360	22,596
Class A Common Stock
Class of Stock [Line Items]
Shares outstanding (in shares)		42,902,824	42,902,824		42,902,824			38,169,575
Remaining shares authorized to purchased (in shares)							24,123
Shares authorized to repurchase (in shares)							2,500,000
Shares repurchased under current authorization (in shares)		0
Stock repurchased and retired (in shares)					0	0
Class B Common Stock
Class of Stock [Line Items]
Shares outstanding (in shares)		22,325,994	22,325,994		22,325,994			22,453,672
Idaho Independent Bank
Class of Stock [Line Items]
Value of common stock consideration issued	$ 157.3
Idaho Independent Bank | Class A Common Stock
Class of Stock [Line Items]
Number of shares issued as consideration (in shares)	3,871,422
Value of common stock consideration issued	$ 157.3
Community 1st Bank | Class A Common Stock
Class of Stock [Line Items]
Number of shares issued as consideration (in shares)	463,134
Value of common stock consideration issued	$ 18.8
Directors | Class A Common Stock
Class of Stock [Line Items]
Shares issued for annual service (in shares)					21,942
Aggregate value of shares issued					$ 0.8