Subsequent Events (Details) $ / shares in Units, $ in Thousands			12 Months Ended
	Jan. 31, 2020 USD ($) office $ / shares shares	Jan. 21, 2020 $ / shares	Dec. 31, 2019 USD ($) $ / shares	Dec. 31, 2018 USD ($)
Subsequent Event [Line Items]
Cash dividend declared (in dollars per share) | $ / shares			$ 0.88
Total assets			$ 11,776,012	$ 11,487,387
Gross loans acquired			8,733,570	8,852,005
Total deposits			8,898,509	$ 8,658,351
Opus | Pro Forma
Subsequent Event [Line Items]
Total assets acquired on a pro forma basis			20,000,000
Opus | Opus
Subsequent Event [Line Items]
Total assets			8,000,000
Gross loans acquired			5,900,000
Total deposits			$ 6,500,000
Subsequent Event
Subsequent Event [Line Items]
Cash dividend declared (in dollars per share) | $ / shares		$ 0.25
Closing price for the Corporation's common stock (in dollars per share) | $ / shares	$ 29.80
Subsequent Event | Opus
Subsequent Event [Line Items]
Consideration paid	$ 1,000,000
Value of company stock (in dollars per share) | $ / shares	$ 26.82
Subsequent Event | Opus | Opus
Subsequent Event [Line Items]
Number of banking offices | office	46
Subsequent Event | Opus | Common Stock
Subsequent Event [Line Items]
Equity issued shares	0.90
Number of shares of common stock issued as consideration (in shares) | shares	34,700,000