Commitments and Contingencies Outstanding Commitments to Extend Credit and Letters of Credit (Details) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Commitments to Extend Credit [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Valuation allowances and reserves, balance	$ 6,688,574	$ 6,306,583
Standby Letters of Credit [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Valuation allowances and reserves, balance	300,262	309,352
Commercial Letters of Credit [Member]
Fair Value, Off-balance Sheet Risks, Disclosure Information [Line Items]
Valuation allowances and reserves, balance	$ 47,368	$ 48,682