Business Combinations - Summary of Estimated Fair Values of Assets Purchased and Liabilities Assumed (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Apr. 07, 2017
Liabilities:
Goodwill	$ 379,627	$ 379,627	$ 379,627
Reliance [Member]
Assets:
Cash and due from banks				$ 5,013
Federal funds sold and securities purchased under reverse repurchase agreements				6,900
Securities				54,843
Acquired loans				117,447
Premises and equipment, net				3,700
Identifiable intangible assets				1,850
Other real estate				475
Other assets				6,037
Total Assets				196,265
Liabilities:
Deposits				166,158
Other borrowings				17,469
Other liabilities				1,322
Total Liabilities				184,949
Net identified assets acquired at fair value				11,316
Goodwill				13,471
Total consideration paid				$ 24,787