Acquisitions (Details) (USD $) In Thousands, except Share data, unless otherwise specified			3 Months Ended
	Jun. 30, 2014	Dec. 31, 2013	Jun. 30, 2014 Mountain West [Member]	Feb. 10, 2014 Class A Common Stock Mountain West [Member]
Significant Acquisitions and Disposals [Line Items]
Number of Subsidiary Banks			1
Number of Shared Markets			5
Total Assets	$ 7,651,379	$ 7,564,651	$ 623,355
Net loans	4,449,699	4,303,992	380,410
Total deposits	$ 6,179,042	$ 6,133,750	$ 519,820
Business Acquisition Conversion Share Rate				0.2552
Business Acquisition Conversion Rate				$ 7.125