Commitments and Contingencies (Off-Balance Sheet Financial Instruments) (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Commitments to Extend Credit [Member]
Loss Contingencies [Line Items]
Contract amounts	$ 7,198,032	$ 7,234,528
Letters of Credit [Member]
Loss Contingencies [Line Items]
Contract amounts	$ 336,419	$ 365,498

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

No definition available.

Name:	us-gaap_LossContingenciesLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration