Acquisitions and Preliminary Purchase Price Allocation Acquisitions and Preliminary Purchase Price Allocation Assets Acquired (Details) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 07, 2018	Dec. 31, 2017
Business Acquisition [Line Items]
Goodwill	$ 108,941,000	$ 109,567,000		$ 76,196,000
Farmers Deposit Bancorp, Inc. [Member]
Business Acquisition [Line Items]
Payments to Acquire Businesses, Gross		24,900,000
Business Combination, Consideration Transferred	24,900,000	24,900,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Cash and Equivalents			$ 4,173,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets, Marketable Securities			46,235,000
Business Combination, Fair Value of Loans Acquired			58,485,000
Business Combination, Purchase Price Allocation, Bank Owned Life Insurance			0
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Property, Plant, and Equipment			568,000
Business Combination Recognized Identifiable Assets Acquired and Liabilities Assumed, Deferred Tax Assets			25,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Other Noncurrent Assets			2,302,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets			111,788,000
Business Combination, Purchase Price Allocation, Deposits			92,241,000
Business Combination, Purchase Price Allocation, Short-Term Debt			2,025,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Noncurrent Liabilities, Long-term Debt			0
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Noncurrent Liabilities, Other			650,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Liabilities			94,916,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net			16,872,000
Goodwill			4,694,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Finite-Lived Intangibles			3,334,000
Poage Bankshares, Inc. [Member]
Business Acquisition [Line Items]
Payments to Acquire Businesses, Gross		16,000
Business Acquisition, Equity Interest Issued or Issuable, Value Assigned			82,565,000
Business Combination, Consideration Transferred, Other		1,355,000
Business Combination, Consideration Transferred	83,936,000	83,936,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Cash and Equivalents			34,325,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets, Marketable Securities			72,321,000
Business Combination, Fair Value of Loans Acquired			304,359,000
Business Combination, Purchase Price Allocation, Bank Owned Life Insurance			7,439,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Property, Plant, and Equipment			4,547,000
Business Combination Recognized Identifiable Assets Acquired and Liabilities Assumed, Deferred Tax Assets			2,454,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Other Noncurrent Assets			8,757,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets			434,202,000
Business Combination, Purchase Price Allocation, Deposits			379,285,000
Business Combination, Purchase Price Allocation, Short-Term Debt			0
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Noncurrent Liabilities, Long-term Debt			4,053,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Noncurrent Liabilities, Other			3,032,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Liabilities			386,370,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net			47,832,000
Goodwill			28,050,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Finite-Lived Intangibles			8,054,000
Poage and Farmers [Member]
Business Acquisition [Line Items]
Payments to Acquire Businesses, Gross		24,916,000
Business Acquisition, Equity Interest Issued or Issuable, Value Assigned			82,565,000
Business Combination, Consideration Transferred, Other		1,355,000
Business Combination, Consideration Transferred	$ 108,836,000	$ 108,836,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Cash and Equivalents			38,498,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets, Marketable Securities			118,556,000
Business Combination, Fair Value of Loans Acquired			362,844,000
Business Combination, Purchase Price Allocation, Bank Owned Life Insurance			7,439,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Property, Plant, and Equipment			5,115,000
Business Combination Recognized Identifiable Assets Acquired and Liabilities Assumed, Deferred Tax Assets			2,479,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Other Noncurrent Assets			11,059,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets			545,990,000
Business Combination, Purchase Price Allocation, Deposits			471,526,000
Business Combination, Purchase Price Allocation, Short-Term Debt			2,025,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Noncurrent Liabilities, Long-term Debt			4,053,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Noncurrent Liabilities, Other			3,682,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Liabilities			481,286,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net			64,704,000
Goodwill			32,744,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Finite-Lived Intangibles			$ 11,388,000