Goodwill and Other Intangible Assets - Change in Other Intangible Assets (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Finite-lived Intangible Assets [Roll Forward]
Balance at the beginning of the period	$ 16,613	$ 20,614	$ 6,088
Additions as a result of acquisitions	0	0	18,345
Amortization	(3,525)	(4,001)	(3,819)
Balance at the end of the period	$ 13,088	$ 16,613	$ 20,614

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://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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