Subsequent Events (Details) $ / shares in Units, $ in Thousands, shares in Millions			3 Months Ended
	Apr. 24, 2020 USD ($) application $ / shares	Jan. 31, 2020 USD ($) $ / shares shares	Mar. 31, 2020 USD ($) $ / shares	Mar. 31, 2019 $ / shares	May 06, 2020 USD ($) loan	Dec. 31, 2019 USD ($)
Subsequent Event [Line Items]
Cash dividends declared (in dollars per share) | $ / shares			$ 0.25	$ 0.22
Closing price of Corporation's common stock | $ / shares		$ 29.80	$ 18.84
Loans held for investment | $			$ 8,754,869			$ 8,722,311
Subsequent Event
Subsequent Event [Line Items]
Cash dividends declared (in dollars per share) | $ / shares	$ 0.25
Subsequent Event | CARES Act
Subsequent Event [Line Items]
Total PPP loans | application	3,700
Total amount in first round of program | $	$ 1,120,000
Number of loans approved for payment deferral | loan					80
Loans held for investment | $					$ 174,800
Opus Bank
Subsequent Event [Line Items]
Consideration paid | $		$ 1,000,000	$ 653,300
Stock transaction value (usd per share) | $ / shares		$ 26.82	$ 16.96
Equity issued, ratio		0.9000
Common stock issued as consideration (in shares) | shares		34.7