Borrowed Funds (Subordinated Debentures Owed to Unconsolidated Subsidiary Trusts) (Narrative) (Details)	1 Months Ended			9 Months Ended		12 Months Ended
	Dec. 31, 2005 USD ($)	Mar. 31, 2004 USD ($)	Oct. 31, 2002 USD ($)	Sep. 30, 2015 USD ($) trust	Sep. 30, 2014 USD ($)	Dec. 31, 2008	Dec. 31, 2014 USD ($)	[1]
Debt Instrument [Line Items]
Number of statutory business trusts | trust				3
Subordinated debentures owed to unconsolidated subsidiary trusts				$ 19,589,000	$ 19,589,000		$ 19,589,000
Net proceeds from issuance of common stock				$ 4,704,000	$ 0
Basis spread on variable rate				0.50%		2.75%
Trust preferred securities limited to tier one capital elements, net of goodwill				25.00%
Sfg Capital Trust I [Member]
Debt Instrument [Line Items]
Ownership percentage			100.00%
Proceeds from issuance or sale of equity			$ 3,500,000
Net proceeds from issuance of common stock			109,000
Payments to acquire debentures			$ 3,610,000
Basis spread on variable rate			3.45%
Sfg Capital Trust Ii [Member]
Debt Instrument [Line Items]
Ownership percentage		100.00%
Proceeds from issuance or sale of equity		$ 7,500,000
Net proceeds from issuance of common stock		232,000
Payments to acquire debentures		$ 7,730,000
Basis spread on variable rate		2.80%
Sfg Capital Trust Iii [Member]
Debt Instrument [Line Items]
Ownership percentage	100.00%
Proceeds from issuance or sale of equity	$ 8,000,000
Net proceeds from issuance of common stock	248,000
Payments to acquire debentures	$ 8,250,000
Basis spread on variable rate	1.45%

[1] December 31, 2014 financial information has been extracted from audited consolidated financial statements