Loans (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended						12 Months Ended
	Sep. 30, 2019	Mar. 31, 2019	Sep. 30, 2018	Mar. 31, 2018	Sep. 30, 2017	Mar. 31, 2017	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans available for sale, unpaid principal amount							$ 1,170,000	$ 685,100
Gains recognized from changes in fair value							963	979	$ 1,800
Changes in fair value related to instrument-specific credit risk							486	829	$ 0
Loans Receivable, Gross, Commercial, Mortgage	$ 778,200	$ 518,300	$ 341,000	$ 304,300	$ 314,400	$ 263,100
Gain (Loss) on Securitization of Financial Assets	14,200	11,200	9,000	11,700	12,000	5,100
Transfers of Financial Assets Accounted for as Sale, Initial Fair Value of Assets Obtained as Proceeds	$ 51,600	$ 41,600	$ 33,700	$ 28,400	$ 24,600	$ 21,700
Fair Value Assumption, Date of Securitization or Asset-backed Financing Arrangement, Transferor's Continuing Involvement, Servicing Assets or Liabilities, Discount Rate	4.12%	4.75%	4.88%	5.79%	9.41%	4.78%
Non-accrual leases							0	0
Interest which would have been earned on loans classified as non-accrual							388	255
Commitments to lend additional funds to loan customers whose terms have been modified in troubled debt restructurings								27
Financing Receivable, Modifications, Post-Modification Recorded Investment							2,084	2,947
Financing Receivable, Troubled Debt Restructured Loans, Reserves							1,000
Receivables Acquired with Deteriorated Credit Quality [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans acquired with deteriorated credit quality							0	0
Estimated Fair Value [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans held for sale							$ 1,180,546	$ 688,471