Commitments and Letters of Credit (Detail 2) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Commitments to Extend Credit
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Legally Binding Commitments	$ 377.2	$ 398.1
Commitments and Letters of Credit	32,768.1	37,247.0
Standby Letters of Credit
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Commitments and Letters of Credit	$ 3,846.1	$ 4,305.4
Weighted average maturity of standby letters of credit	24 months	24 months
Secured by Cash Deposits or Participated to Others | Standby Letters of Credit
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Commitments and Letters of Credit	$ 134.2	$ 147.1