Allowance for Loan Losses Allowance for Loan Losses Text Disclosures (Details) - USD ($)	Sep. 30, 2017	Jun. 30, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Dec. 31, 2015
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans and Leases Receivable, Net of Deferred Income	$ 6,413,201,000		$ 6,114,354,000
Loans and Leases Receivable, Allowance	74,873,000	$ 75,009,000	78,077,000	$ 77,669,000	$ 75,753,000	$ 78,500,000
Receivables Acquired with Deteriorated Credit Quality [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Loans and Leases Receivable, Net of Deferred Income	$ 0		$ 0