Fair Value Measurements (Narrative) (Details) (USD $)	9 Months Ended	12 Months Ended
	Sep. 30, 2014	Dec. 31, 2013
Finite-Lived Intangible Assets [Line Items]
Private equity investment Southwest's proportionate share of the net asset value	$ 2,500,000	$ 2,400,000
Impaired loans carrying amount	26,100,000	47,000,000
Impaired loans measured at fair value	20,100,000	33,700,000
Impaired loans life to date impairment	6,000,000	13,300,000
Provision for loan losses		50,000
Impairment charges		0
Noncovered [Member]
Finite-Lived Intangible Assets [Line Items]
Provision for loan losses	4,600,000
Covered And Noncovered [Member]
Finite-Lived Intangible Assets [Line Items]
Impairment charge of other real estate assets	300,000	2,200,000
Core Deposits [Member]
Finite-Lived Intangible Assets [Line Items]
Impairment charges	$ 1,100,000