Summary of Significant Accounting Policies - Additional Information (Details)	12 Months Ended
	Dec. 31, 2016 USD ($) segment entity subsidiary	Mar. 04, 2016 USD ($)	Dec. 31, 2015 USD ($)	Mar. 04, 2015 USD ($)
Summary of Significant Accounting Policies [Line Items]
Number of subsidiary | subsidiary	3
Percentage of outstanding common stock of investees accounted for using equity method of accounting	100.00%
Prior period reclassification adjustment	$ 0
Number of entities non-banking activities | entity	5
Period for satisfactory payment of TDRs	6 months
Evaluation for impairment of substandard and nonaccrual commercial loans	$ 500,000
Number of reporting units | segment	3
Goodwill	$ 291,670,000		$ 291,764,000
Amortization period of intangible assets	10 years
Percentage of amount recognized of tax benefit	50.00%
Community Banking
Summary of Significant Accounting Policies [Line Items]
Goodwill	$ 287,400,000
Percentage of goodwill to reporting units	99.00%
Insurance
Summary of Significant Accounting Policies [Line Items]
Goodwill	$ 4,200,000
Percentage of goodwill to reporting units	1.00%
Interest Rate Lock Commitments
Summary of Significant Accounting Policies [Line Items]
Period for interest rate lock commitment	60 days
Integrity Bancshares, Inc.
Summary of Significant Accounting Policies [Line Items]
Goodwill		$ 115,850,000		$ 115,900,000
Common Wealth Trust Life Insurance Company
Summary of Significant Accounting Policies [Line Items]
Percentage of outstanding common stock of investees accounted for using equity method of accounting	50.00%
Minimum
Summary of Significant Accounting Policies [Line Items]
Percentage of outstanding common stock of investees accounted for using equity method of accounting	20.00%
Maximum
Summary of Significant Accounting Policies [Line Items]
Percentage of outstanding common stock of investees accounted for using equity method of accounting	50.00%
Core Deposits And Customers Lists | Minimum
Summary of Significant Accounting Policies [Line Items]
Acquired finite-lived intangibles, weighted average life	10 years
Core Deposits And Customers Lists | Maximum
Summary of Significant Accounting Policies [Line Items]
Acquired finite-lived intangibles, weighted average life	20 years
Corporate Joint Venture [Member]
Summary of Significant Accounting Policies [Line Items]
Percentage of outstanding common stock of investees accounted for using equity method of accounting	50.00%