Acquisitions - Additional Information (Details) - USD ($) $ / shares in Units, $ in Thousands			3 Months Ended		6 Months Ended
	Mar. 09, 2020	May 09, 2019	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Jan. 16, 2019
Business Acquisition [Line Items]
Acquisition and integration related expenses			$ 5,249	$ 9,514	$ 10,721	$ 13,205
Bankmanagers Corporation
Business Acquisition [Line Items]
Total assets	$ 1,151,236
Total deposits	950,076
Loans	$ 685,451
Fixed exchange ratio (in shares)	29.9675
Cash paid per share (in dollars per share)	$ 623.02
Special dividends paid (in dollars per share)	$ 346.00
Consideration transferred	$ 174,382
Common stock, shares issued (in shares)	4,930,231
Cash paid	$ 102,499
Goodwill	$ 62,433
Bridgeview Bancorp, Inc.
Business Acquisition [Line Items]
Total assets		$ 1,165,815
Total deposits		986,754
Loans		$ 709,438
Fixed exchange ratio (in shares)		0.2767
Cash paid per share (in dollars per share)		$ 1.66
Consideration transferred		$ 135,352
Common stock, shares issued (in shares)		4,728,541
Cash paid		$ 37,140
Goodwill		$ 63,231
Northern Oak Wealth Management, Inc.
Business Acquisition [Line Items]
Assets under management acquired							$ 800,000