Subsequent Events (Details) - Subsequent Event $ / shares in Units, shares in Millions, $ in Millions			3 Months Ended
	Aug. 03, 2017 USD ($) $ / shares shares	Jul. 26, 2017 USD ($) branch $ / shares	Mar. 31, 2018 USD ($)
Series B Preferred Stock
Subsequent Event [Line Items]
Liquidation preference (usd per share) | $ / shares	$ 25
Preferred stock dividend rate	5.50%
Proceeds from issuance of preferred stock after deducting underwriting discounts, commissions and offering expenses	$ 98.1
Series B Preferred Stock | LIBOR
Subsequent Event [Line Items]
Preferred stock dividend rate, basis spread on variable rate	3.578%
Series B Preferred Stock | Preferred Stock
Subsequent Event [Line Items]
Shares issued (in shares) | shares	4.0
Shares issued	$ 100.0
USAmeriBancorp, Inc. (USAB)
Subsequent Event [Line Items]
Assets acquired		$ 4,400.0
Loans acquired		3,600.0
Deposits acquired		$ 3,500.0
Number of branches acquired (in branch) | branch		30
Share ratio of common stock issued to USAB shareholders		6.1
USAmeriBancorp, Inc. (USAB) | Forecast
Subsequent Event [Line Items]
Consideration transferred			$ 816.0
USAmeriBancorp, Inc. (USAB) | Minimum
Subsequent Event [Line Items]
Stock price (usd per share) | $ / shares		$ 11.50
Walkaway rights, weighted-average share price (usd per share) | $ / shares		11
USAmeriBancorp, Inc. (USAB) | Maximum
Subsequent Event [Line Items]
Stock price (usd per share) | $ / shares		13.00
Walkaway rights, weighted-average share price (usd per share) | $ / shares		$ 13.50