Business Combinations - Additional Information (Detail) (USD $)			0 Months Ended		3 Months Ended
	Mar. 31, 2014	Dec. 31, 2013	Nov. 25, 2013 First Wyoming Financial Corporation [Member]	Sep. 30, 2013 First Wyoming Financial Corporation [Member] Office	Mar. 31, 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	4,545,962,000	4,515,763,000		307,700,000
Total deposits	3,173,082,000	3,186,942,000		249,700,000
Total purchase price					8,000,000
Payments 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					$ 2,353,000
Amortization period for intangible assets					7 years