Business Combinations - Additional Information (Detail) (USD $)			0 Months Ended		6 Months Ended
	Jun. 30, 2014	Dec. 31, 2013	Nov. 25, 2013 First Wyoming Financial Corporation [Member]	Dec. 31, 2013 First Wyoming Financial Corporation [Member] Office	Jun. 30, 2014 Array Financial Group, Inc. [Member]
Business Acquisition [Line Items]
Transaction value, cash and stock			$ 64,000,000
Number of banking offices				6
Total assets	4,613,090,000	4,515,763,000		302,800,000
Total deposits	3,153,329,000	3,186,942,000		244,500,000
Total purchase price					8,000,000
Payment for working capital					1,400,000
Earn out amount of purchase price					4,000,000
Earn out period					5 years
Fair value of consideration paid					2,600,000
Intangible assets recognized					$ 2,400,000
Amortization period for intangible assets					7 years