Revenue from Contracts with Customers Revenue from Contracts with Customers (Schedule of Trust Fees) (Details) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Trust Fees [Line Items]
Trust fees	$ 37,036	$ 33,120	$ 73,098	$ 65,134
Private Client [Member]
Trust Fees [Line Items]
Trust fees	27,987	24,701	54,855	48,463
Institutional [Member]
Trust Fees [Line Items]
Trust fees	7,271	6,751	14,682	13,245
Other Trust Fees [Member]
Trust Fees [Line Items]
Trust fees	$ 1,778	$ 1,668	$ 3,561	$ 3,426

Income from services rendered by trust departments or by any consolidated subsidiaries acting in a fiduciary capacity, including fees earned for (1) acting as an agent for fiduciary placement and loans and (2) custody or investment advisory services when such fees are not separately billed to the customer. This item excludes commissions and fees received for the accumulation or disbursement of funds deposited to Individual Retirement or Keogh plan accounts when such are not handled by the reporting entity's trust department.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 225
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-04.13 (a))
-URI http://asc.fasb.org/extlink&oid=6879574&loc=d3e536633-122882

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration