Guarantees and Off-Balance Sheet Arrangements Details (Tables)

12 Months Ended

Dec. 31, 2017

Guarantees and Off Balance Sheet Arrangements [Abstract]

Schedule of Subordinated Borrowing [Table Text Block]

The Company maintains uncommitted financing arrangements with large financial institutions, the details of which are summarized below as of December 31, 2017.

Lender	Contractual Amount		Available Amount		Maturity Date	Description
Pledge Lines	(dollars in thousands)
BMO Harris Bank	$	150,000	$	150,000	None	Secured DTC Pledge Line
Total	150,000		150,000
Revolving Credit Facility
BMO Harris Bank	30,000		30,000		August 2, 2018	Unsecured liquidity facility to cover increases in NSCC margin deposit requirements
Total Credit Lines	$	180,000	$	180,000