Acquisitions and Preliminary Purchase Price Allocation Acquisitions and Preliminary Purchase Price Allocation Assets Acquired (Details) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 07, 2018	Dec. 31, 2017	Dec. 31, 2016
Business Acquisition [Line Items]
Goodwill	$ 109,567,000		$ 76,196,000	$ 76,196,000
Farmers Deposit Bancorp, Inc. [Member]
Business Acquisition [Line Items]
Payments to Acquire Businesses, Gross	24,900,000.00
Business Combination, Consideration Transferred	24,900,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Cash and Equivalents		$ 4,209,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets, Marketable Securities		46,235,000
Business Combination, Fair Value of Loans Acquired		58,477,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Property, Plant, and Equipment		768,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Deferred Tax Liabilities		(188,000)
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		111,803,000
Business Acquisition, 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, Other		709,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Liabilities		94,975,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net		16,828,000
Goodwill		4,738,000
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 Combination, Consideration Transferred, Other	1,355,000
Business Combination, Consideration Transferred	83,936,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Cash and Equivalents		34,288,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets, Marketable Securities		72,321,000
Business Combination, Fair Value of Loans Acquired		304,023,000
Business Acquisition, 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		2,300,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Other Noncurrent Assets		8,799,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets		433,717,000
Business Acquisition, Purchase Price Allocation, Deposits		379,285,000
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		3,130,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Liabilities		386,468,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net		47,249,000
Goodwill		28,633,000
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 Combination, Consideration Transferred, Other	1,355,000
Business Combination, Consideration Transferred	$ 108,836,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Cash and Equivalents		38,497,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Current Assets, Marketable Securities		118,556,000
Business Combination, Fair Value of Loans Acquired		362,500,000
Business Acquisition, Purchase Price Allocation, Bank Owned Life Insurance		7,439,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Property, Plant, and Equipment		5,315,000
Business Combination Recognized Identifiable Assets Acquired and Liabilities Assumed, Deferred Tax Assets		2,112,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Other Noncurrent Assets		11,101,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets		545,520,000
Business Acquisition, 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		3,839,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Liabilities		481,443,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net		64,077,000
Goodwill		33,371,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Finite-Lived Intangibles		$ 11,388,000