FHLB Advances, Other Borrowings and Subordinated Notes (Narrative) (Details) $ in Millions	1 Months Ended			6 Months Ended
	Jun. 30, 2018 CAD ($)	Dec. 31, 2017 CAD ($)	Dec. 31, 2015 CAD ($)	Jun. 30, 2018 USD ($) Rate	Jun. 30, 2018 CAD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2017 CAD ($)	Jun. 30, 2017 USD ($)	Dec. 31, 2014 CAD ($)	Dec. 15, 2014 USD ($)
Debt Instrument [Line Items]
Notes payable				$ 29,982,000		$ 41,222,000		$ 44,959,000
Loan agreement with unaffiliated banks				150,000,000
Short-term borrowings				21,437,000		17,209,000		46,280,000
Other				48,369,000		49,131,000		49,765,000
Secured borrowings				155,913,000		158,561,000		136,706,000
Subordinated notes				$ 139,148,000		139,088,000		139,029,000
Base Rate Loan | Federal Funds Rate
Debt Instrument [Line Items]
Basis spread on variable rate				0.50%
Base Rate Loan | Eurodollar Rate
Debt Instrument [Line Items]
Basis spread on variable rate				1.00%
Term Facility
Debt Instrument [Line Items]
Notes payable				$ 30,000,000		41,200,000		45,000,000		$ 75,000,000
Term Facility | Base Rate Loan | Base Rate
Debt Instrument [Line Items]
Basis spread on variable rate				0.75%
Term Facility | Eurodollar Rate Loan | Eurodollar Rate
Debt Instrument [Line Items]
Basis spread on variable rate				1.75%
Revolving Credit Facility
Debt Instrument [Line Items]
Notes payable				$ 0		0		0
Maximum borrowing capacity										$ 75,000,000.0
Commitment fee (as a percent) | 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 | Eurodollar Rate
Debt Instrument [Line Items]
Basis spread on variable rate				1.50%
Securities sold under repurchase agreements
Debt Instrument [Line Items]
Securities sold under agreements to repurchase				$ 21,400,000		17,200,000		46,300,000
Pledged financial instruments				43,200,000
Fixed Rate Promissory Note
Debt Instrument [Line Items]
Other				$ 48,400,000		49,000,000		49,500,000
Fixed rate (as a percent)				3.36%	3.36%
Non Recourse Debt
Debt Instrument [Line Items]
Other				$ 12,000		151,000		300,000
Secured Debt
Debt Instrument [Line Items]
Secured borrowings				$ 11,300,000
Secured Debt | Receivables Purchase Agreement
Debt Instrument [Line Items]
Fixed rate (as a percent)				2.4874%	2.4874%
Secured borrowings			$ 160	$ 144,600,000	$ 190	$ 135,100,000	$ 170	$ 123,400,000	$ 150
Additional amount paid by third party	$ 20	$ 10	$ 10
Subordinated Debt
Debt Instrument [Line Items]
Fixed rate (as a percent)				5.00%	5.00%