Subsequent Event (Details Textual) - USD ($)		6 Months Ended
		Jun. 30, 2015	Jul. 30, 2015	Dec. 31, 2014
Subsequent Event
Subsequent Event, Date		Jul. 30, 2015
Subsequent Event, Description		the Company announced the signing of a definitive agreement to acquire Cañon National Bank, a community bank based in Cañon City, Colorado
Total assets		$ 8,589,810,000		$ 8,306,507,000
Gross loans	[1]	$ 4,807,431,000		$ 4,488,095,000
Canon National Bank
Subsequent Event
Total assets			$ 253,000,000
Gross loans			159,000,000
Total deposits			$ 225,000,000

[1] Includes net deferred fees, costs, premiums and discounts of $13,312,000 and $13,710,000 at June 30, 2015 and December 31, 2014, respectively.