Fair Value Measurements (Narrative) (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Finite-Lived Intangible Assets [Line Items]
Private equity investment Southwest's proportionate share of the net asset value	$ 0	$ 2,400,000
Impairment charges	0	0
Noncovered [Member]
Finite-Lived Intangible Assets [Line Items]
Noncovered impaired loans carrying amount	21,900,000	47,000,000
Noncovered impaired loans measured at fair value	17,500,000	33,700,000
Noncovered impaired loans life to date impairment	4,400,000	13,300,000
Impairment charge of other real estate assets	$ 600,000	$ 2,200,000