Trust Preferred Securities and Subordinated Debentures (Narrative) (Details) - USD ($)			12 Months Ended
	Oct. 14, 2003	Jun. 26, 2003	Dec. 31, 2016	Dec. 31, 2015	Sep. 04, 2003
Subordinated Borrowing [Line Items]
Trust Preferred Securities			$ 45,000,000	$ 50,000,000
Subordinated debentures			46,393,000	51,548,000
Investment in common equity issued by Trusts			$ 1,400,000
Federal Reserve Limit On Trust Preferred			25.00%
OKSB Statutory Trust I [Member]
Subordinated Borrowing [Line Items]
Trust Preferred Securities		$ 20,000,000	$ 20,000,000	20,000,000
Adjustable rate			90-day LIBOR
Adjustable rate, additional percentage			3.10%
Amount of trust common equity sold to Southwest		$ 600,000
Subordinated debentures			$ 20,619,000	20,619,000
Outstanding common securities of the Trust		619
Trust liquidation value per share		$ 1,000
SBI Capital Trust II [Member]
Subordinated Borrowing [Line Items]
Trust Preferred Securities	$ 25,000,000		$ 25,000,000	25,000,000
Adjustable rate			90-day LIBOR
Adjustable rate, additional percentage			2.85%
Amount of trust common equity sold to Southwest	$ 800,000
Subordinated debentures			$ 25,774,000	25,774,000
Outstanding common securities of the Trust	774
Trust liquidation value per share	$ 1,000
FCBI Statutory Trust I [Member]
Subordinated Borrowing [Line Items]
Trust Preferred Securities				5,000,000	$ 5,000,000
Adjustable rate			90-day LIBOR
Adjustable rate, additional percentage			3.00%
Amount of trust common equity sold to Southwest					200,000
Subordinated debentures				$ 5,155,000
OKSB Subordinated Debentures [Member]
Subordinated Borrowing [Line Items]
Adjustable rate			90-day LIBOR
Adjustable rate, additional percentage			3.10%
Principal amount of subordinated debentures		$ 20,600,000
SBI II Subordinated Debentures [Member]
Subordinated Borrowing [Line Items]
Adjustable rate			90-day LIBOR
Adjustable rate, additional percentage			2.85%
Principal amount of subordinated debentures	$ 25,800,000
FCBI I Subordinated Debentures [Member]
Subordinated Borrowing [Line Items]
Adjustable rate			90-day LIBOR
Adjustable rate, additional percentage			3.00%
Principal amount of subordinated debentures					$ 5,200,000
Trust Preferred Securities [Member]
Subordinated Borrowing [Line Items]
Tier one capital			$ 45,000,000