Goodwill and Intangible Assets (Narrative) (Detail) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Acquired Finite-Lived Intangible Assets [Line Items]
Amortizing the core deposit intangibles	7 years
Intangible amortization expense, 2012	$ 5,300,000
Intangible amortization expense, 2013	5,300,000
Intangible amortization expense, 2014	5,300,000
Intangible amortization expense, 2015	5,300,000
Intangible amortization expense, 2016	5,300,000
Intangible amortization expense, 2017	5,300,000
Intangible amortization expense through 2018	1,000,000
Intangible amortization expense	5,300,000	4,400,000	0
Goodwill	59,630,000	59,630,000	52,400,000
Hillcrest Bank, N.A. [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Intangible assets	5,800,000
Bank Midwest, N.A. [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Intangible assets	21,700,000
Bank Of Choice [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Intangible assets	5,200,000
Community Banks Of Colorado [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Intangible assets	4,800,000
Goodwill		$ 7,200,000