Derivative Instruments (Details) (USD $)	9 Months Ended		12 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013
Derivative [Line Items]
Interest payment period	7 years
Fixed interest rate	6.15%
Rate received by Southwest	3.08%
Pretax loss related to derivative contracts	$ 1,600,000		$ 2,000,000
Gain or loss due to changes in the fair value of the derivative hedging instrument	200,000	600,000
Net cash flows as a result of the interest rate swap agreement	600,000	600,000
Interest Rate Swap [Member]
Derivative [Line Items]
Interest rate swap agreement Notional amount	25,000,000
Variable interest rate	2.85%
The fair value of cash and securities posted as collateral	4,100,000
Customer Risk Management Swaps [Member]
Derivative [Line Items]
Number of customer interest rate swap agreements	two
Interest rate swap agreement Notional amount	19,700,000
Variable interest rate	2.97%
Non-Hedge Derivative Asset [Member]
Derivative [Line Items]
Interest rate swap agreement Notional amount	19,723,000
Fair Value Net of Cash Collateral	166,000
Non-hedge derivative asset, fair value	166,000
Non-Hedge Derivative Liability [Member]
Derivative [Line Items]
Interest rate swap agreement Notional amount	19,723,000
Fair Value Net of Cash Collateral	166,000
Non-hedge derivative liability, fair value	$ 166,000