Financial Instruments with Off-Balance Sheet Risk (Details) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
Entity Information [Line Items]
Credit extension commitments		$ 2,637.1
Unused Credit Card Lines
Entity Information [Line Items]
Credit extension commitments		720.7
Credit extension commitments beyond one year	$ 1,058.9
Standby Letters of Credit
Entity Information [Line Items]
Credit extension commitments		$ 47.6