Note 6 - Goodwill and Other Intangible Assets (Details Textual) - USD ($)	3 Months Ended		6 Months Ended	12 Months Ended
	Jun. 30, 2017	Dec. 31, 2016	Jun. 30, 2017	Dec. 31, 2016	May 15, 2017	Sep. 09, 2016
Goodwill	$ 379,437,000	$ 348,505,000	$ 379,437,000	$ 348,505,000
Goodwill, Impairment Loss			$ 0	$ 0
Minimum [Member]
Finite-Lived Intangible Asset, Useful Life			10 years
Maximum [Member]
Finite-Lived Intangible Asset, Useful Life			15 years
Core Deposit Premium [Member]
Finite-Lived Intangible Asset, Useful Life			10 years
Hardeman County Investment Company, Inc. [Member]
Goodwill					$ 29,402,000	$ 23,000,000
Finite-lived Intangible Assets Acquired	830,000
Hardeman County Investment Company, Inc. [Member] | Core Deposit Premium [Member]
Finite-lived Intangible Assets Acquired	$ 7,800,000
Citizens National Bank [Member]
Goodwill						$ 23,025,000
Finite-lived Intangible Assets Acquired		591,000
Citizens National Bank [Member] | Core Deposit Premium [Member]
Finite-lived Intangible Assets Acquired		$ 5,100,000