Subordinated Debt Securities (Narrative) (Details) - USD ($) $ in Millions				12 Months Ended	120 Months Ended	121 Months Ended
	Aug. 23, 2007	Jun. 21, 2005	Jun. 21, 2005	Dec. 31, 2017	Jun. 15, 2015	Sep. 15, 2017	Dec. 31, 2016
Subordinated Debt [Member]
Subordinated Borrowing [Line Items]
Long-term debt, gross				$ 55.8			$ 55.7
Hallmark Statutory Trust I [Member]
Subordinated Borrowing [Line Items]
Long-term debt, gross		$ 30.9	$ 30.9	$ 30.9
Proceeds from issuance of trust preferred securities		30.0
Proceeds from issuance of common stock		$ 0.9
Subordinated borrowing, interest rate				4.84%	7.725%
Debt instrument interest rate fixed to floating date		Jun. 15, 2015
Hallmark Statutory Trust I [Member] | Subordinated Debt [Member]
Subordinated Borrowing [Line Items]
Long-term debt, gross		$ 30.9	30.9
Proceeds from issuance of trust preferred securities			$ 30.0
Hallmark Statutory Trust I I [Member]
Subordinated Borrowing [Line Items]
Long-term debt, gross	$ 25.8			$ 25.8
Proceeds from issuance of trust preferred securities	25.0
Proceeds from issuance of common stock	0.8
Subordinated borrowing, interest rate				4.49%		8.28%
Hallmark Statutory Trust I I [Member] | Subordinated Debt [Member]
Subordinated Borrowing [Line Items]
Long-term debt, gross	25.8
Proceeds from issuance of trust preferred securities	$ 25.0
London Interbank Offered Rate (LIBOR) [Member] | Hallmark Statutory Trust I [Member]
Subordinated Borrowing [Line Items]
Debt instrument, basis spread on variable rate				3.25%
London Interbank Offered Rate (LIBOR) [Member] | Hallmark Statutory Trust I I [Member]
Subordinated Borrowing [Line Items]
Subordinated borrowing, interest rate				2.90%