Document And Entity Information (USD $)	12 Months Ended
	Dec. 31, 2014	Mar. 10, 2015	Jun. 30, 2014
Document And Entity Information [Abstract]
Entity Registrant Name	SOUTHWEST BANCORP INC
Entity Central Index Key	0000914374
Document Type	10-K
Document Period End Date	Dec. 31, 2014
Amendment Flag	false
Document Fiscal Year Focus	2014
Document Fiscal Period Focus	FY
Current Fiscal Year End Date	--12-31
Trading Symbol	oksb
Entity Filer Category	Accelerated Filer
Entity Public Float			$ 323,400,000
Entity Common Stock, Shares Outstanding		19,042,409
Entity Voluntary Filers	No
Entity Well-known Seasoned Issuer	No
Entity Current Reporting Status	Yes