Acquisitions (Details) (USD $) In Thousands, except Share data, unless otherwise specified			3 Months Ended
	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2014 Mountain West [Member]	Mar. 31, 2014 Mountain West [Member]	Mar. 31, 2014 Class A Common Stock	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
Loans held for investment	$ 4,326,367	$ 4,303,992	$ 405,409
Deposits	6,135,137	6,133,750	539,920
Business Acquisition Conversion Share Rate						0.2552
Business Acquisition Conversion Rate						$ 7.125
Share Price					$ 28.22
Estimate of Payments to Acquire Businesses, Total				78,814
Estimate of Payments to Acquire Businesses, Gross				39,920
Business Acquisitions Pending, Estimate of Equity Interest Issued or Issuable, Value Assigned				$ 38,894
Business Acquisition Pending, Equity Interest Issued or Issuable, Number of Shares				1,378,230