Borrowed Funds (Subordinated Debentures Owed to Unconsolidated Subsidiary Trusts) (Narrative) (Details) $ in Thousands	1 Months Ended			12 Months Ended
	Dec. 31, 2005 USD ($)	Mar. 31, 2004 USD ($)	Oct. 31, 2002 USD ($)	Dec. 31, 2017 USD ($) trust	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Debt Instrument [Line Items]
Number of Statutory Business Trusts | trust				3
Subordinated debentures owed to unconsolidated subsidiary trusts				$ 19,589	$ 19,589
Ownership percentage				100.00%
Net proceeds from issuance of common stock				$ 10	$ 101	$ 4,772
Basis spread on variable rate				0.50%
Trust preferred securities limited to tier one capital elements, Nnt of goodwill				25.00%
Sfg Capital Trust I [Member]
Debt Instrument [Line Items]
Proceeds from issuance or sale of equity			$ 3,500
Net proceeds from issuance of common stock			109
Payments to acquire investments			$ 3,610
Basis spread on variable rate			3.45%
Sfg Capital Trust Ii [Member]
Debt Instrument [Line Items]
Proceeds from issuance or sale of equity		$ 7,500
Net proceeds from issuance of common stock		232
Payments to acquire investments		$ 7,730
Basis spread on variable rate		2.80%
Sfg Capital Trust Iii [Member]
Debt Instrument [Line Items]
Proceeds from issuance or sale of equity	$ 8,000
Net proceeds from issuance of common stock	248
Payments to acquire investments	$ 8,250
Basis spread on variable rate	1.45%