Revenue from Contracts with Customers Revenue from Contracts with Customers (Schedule of Trust Fees) (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Trust Fees [Line Items]
Trust fees	$ 37,400	$ 34,620	$ 110,498	$ 99,754
Private Client [Member]
Trust Fees [Line Items]
Trust fees	28,210	25,689	83,065	74,152
Institutional [Member]
Trust Fees [Line Items]
Trust fees	7,388	7,027	22,070	20,272
Other Trust Fees [Member]
Trust Fees [Line Items]
Trust fees	$ 1,802	$ 1,904	$ 5,363	$ 5,330

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