Note Loans (Carrying amount of acquired loans accounted for pursuant to ASC310-30 by portfolio) (Details) - ASC Subtopic 310-30 - USD ($) $ in Thousands	Sep. 30, 2018		Jun. 30, 2018	Dec. 31, 2017	Sep. 30, 2017		Jun. 30, 2017	Dec. 31, 2016
Accounts, Notes, Loans and Financing Receivable [Line Items]
Carrying amount	$ 1,990,622	[1]	$ 2,033,457	$ 2,108,993	$ 2,133,946	[1]	$ 2,168,664	$ 2,301,024
Less: Allowance for loan losses	(168,559)			(119,505)	(138,030)
Carrying amount, net of allowance	1,822,063			1,989,488	$ 1,995,916
Commercial real estate
Accounts, Notes, Loans and Financing Receivable [Line Items]
Carrying amount	876,521			923,424
Commercial and industrial
Accounts, Notes, Loans and Financing Receivable [Line Items]
Carrying amount	86,000			88,130
Construction
Accounts, Notes, Loans and Financing Receivable [Line Items]
Carrying amount	0			170
Mortgages
Accounts, Notes, Loans and Financing Receivable [Line Items]
Carrying amount	1,012,789			1,079,611
Consumer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Carrying amount	$ 15,312			$ 17,658

[1] At September 30, 2018, includes $1.5 billion of loans considered non-credit impaired at the acquisition date (September 30, 2017 - $1.6 billion).