Mergers and Acquisitions (Details) - USD ($) $ / shares in Units, $ in Thousands		12 Months Ended
	Jul. 01, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Business Acquisition [Line Items]
Value of stock paid		$ 213,590	$ 55,290	$ 281,530
Net Assets Acquired:
Goodwill		$ 611,046	$ 470,534	$ 445,871
Metropolitan Bancgroup, Inc.
Business Acquisition [Line Items]
Shares issued to common shareholders (shares)	4,883,182
Fair value of common stock on date of issuance (usd per share)	$ 43.74
Value of stock paid	$ 213,590
Cash paid for fractional shares	5
Cash settlement for stock options	4,764
Deal charges paid on behalf of Metropolitan, net of taxes	1,102
Total Purchase Price	219,461
Net Assets Acquired:
Securities	(731)
Mortgage loans held for sale	30
Loans, net of Metropolitan’s allowance for loan losses	(13,071)
Premises and equipment	(4,629)
Intangible assets, net of Metropolitan’s existing intangibles	2,340
Other real estate owned	(1,251)
Other assets	2,731
Deposits	(3,603)
Borrowings	(1,294)
Other liabilities	3,930
Deferred income taxes	5,244
Total net assets acquired	78,949
Goodwill	140,512
Metropolitan Bancgroup, Inc. | Metropolitan Bancgroup, Inc.
Net Assets Acquired:
Stockholders’ equity at acquisition date	$ 89,253