The aggregate expense charged against earnings to allocate the cost of intangible assets (nonphysical assets not used in production) in a systematic and rational manner to the periods expected to benefit from such assets. As a noncash expense, this element is added back to net income when calculating cash provided by or used in operations using the indirect method.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
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-Section 45
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Reference 2: http://www.xbrl.org/2003/role/presentationRef
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Amount of amortization expense for assets, excluding financial assets and goodwill, lacking physical substance with a finite life expected to be recognized during the third fiscal year following the latest fiscal year. Excludes interim and annual periods when interim periods are reported on a rolling approach, from latest balance sheet date.

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Amount after amortization of assets, excluding financial assets and goodwill, lacking physical substance with a finite life.

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Goodwill and Other Intangible Assets (Amortization Expense of Core Deposit Intangibles) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Goodwill and Intangible Assets Disclosure [Abstract]
Amortization expense	$ 1,400	$ 1,800	$ 2,900	$ 3,600
Core Deposit Intangibles
Year Ended December 31,
Remainder of 2018	2,635		2,635
2019	4,518		4,518
2020	3,634		3,634
2021	2,749		2,749
2022	1,865		1,865
Thereafter	1,763		1,763
Net carrying balance	$ 17,164		$ 17,164		$ 21,054