FHLB Advances, Other Borrowings and Subordinated Notes (Narrative) (Details) $ in Millions	1 Months Ended					3 Months Ended	24 Months Ended	48 Months Ended	54 Months Ended	62 Months Ended
	Feb. 28, 2019 CAD ($)	Jun. 30, 2018 CAD ($)	Dec. 31, 2017 CAD ($)	Dec. 31, 2015 CAD ($)	Dec. 31, 2014 CAD ($)	Mar. 31, 2019 USD ($) building Rate	Dec. 31, 2015 CAD ($)	Dec. 31, 2017 CAD ($)	Jun. 30, 2018 CAD ($)	Feb. 28, 2019 CAD ($)	Dec. 31, 2018 USD ($)	Sep. 18, 2018 USD ($)	Mar. 31, 2018 USD ($)	Dec. 15, 2014 USD ($)
Debt Instrument [Line Items]
Notes payable						$ 139,119,000					$ 144,461,000	$ 150,000,000	$ 33,727,000	$ 150,000,000
Short-term borrowings						16,212,000					50,593,000		17,977,000
Other borrowings						47,394,000					47,722,000		48,742,000
Secured borrowings						169,469,000					151,079,000		146,646,000
Subordinated notes						139,235,000					139,210,000		139,111,000
Revolving Credit Facility
Debt Instrument [Line Items]
Notes payable												50,000,000		75,000,000
Amount outstanding						0
Term Facility
Debt Instrument [Line Items]
Notes payable						$ 139,100,000						150,000,000	33,700,000	$ 75,000,000
Base Rate Loan | Federal Funds Rate
Debt Instrument [Line Items]
Basis spread on variable rate						0.50%
Base Rate Loan | London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Basis spread on variable rate						1.00%
Line of Credit | Credit Agreement
Debt Instrument [Line Items]
Loan agreement with unaffiliated banks												$ 200,000,000
Term Facility | Base Rate Loan | Base Rate
Debt Instrument [Line Items]
Basis spread on variable rate						0.75%
Term Facility | Eurodollar Rate Loan | London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Basis spread on variable rate						1.25%
Revolving Credit Facility
Debt Instrument [Line Items]
Commitment fee | Rate						0.20%
Revolving Credit Facility | Base Rate Loan | Base Rate
Debt Instrument [Line Items]
Basis spread on variable rate						0.50%
Revolving Credit Facility | Eurodollar Rate Loan | London Interbank Offered Rate (LIBOR)
Debt Instrument [Line Items]
Basis spread on variable rate						1.25%
Securities sold under repurchase agreements
Debt Instrument [Line Items]
Securities sold under agreements to repurchase						$ 16,200,000					50,600,000		18,000,000
Pledged financial instruments						$ 53,300,000
Fixed Rate Promissory Note
Debt Instrument [Line Items]
Number of properties securing debt | building						2
Other borrowings						$ 47,400,000					47,700,000		48,700,000
Fixed interest rate						3.36%
Secured Debt
Debt Instrument [Line Items]
Secured borrowings						$ 12,300,000
Secured Debt | Receivables Purchase Agreement
Debt Instrument [Line Items]
Fixed interest rate						2.9398%
Proceeds from debt issuance	$ 20	$ 20	$ 10	$ 10	$ 150		$ 160	$ 170	$ 190	$ 210
Secured borrowings						$ 157,200,000					$ 139,300,000		$ 131,700,000
Subordinated Debt
Debt Instrument [Line Items]
Fixed interest rate						5.00%