Acquisitions (Narrative) (Details) $ in Thousands			12 Months Ended
	Dec. 14, 2016 USD ($) shares	Oct. 09, 2015 USD ($) item shares	Dec. 31, 2016 USD ($) entity item	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
Business Acquisition [Line Items]
Number of total branches | item			1
Business Combination, Consideration Transferred	$ 564,400
Assets, Total			$ 2,475,392	$ 2,357,022	$ 1,214
Deposits, Total			1,946,018	1,884,105	1,533,999
Business Acquisition, Equity Interest Issued or Issuable, Number of Shares | shares	7,250,000
Payments to Acquire Businesses, Gross	$ 95,000
Business Combination, Fair Value Of Assets Acquired		$ 301,500
Goodwill		12,300	$ 13,545	$ 13,467	$ 1,942,034
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Deposits		245,200
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill		$ 2,700
Effective tax rate			35.70%	36.00%	37.50%
Oklahoma City [Member]
Business Acquisition [Line Items]
Number of branches acquired | entity			5
Number of total branches		10	10
Denver [Member]
Business Acquisition [Line Items]
Number of branches acquired | entity			3
Number of total branches | entity			1
Parent Company [Member]
Business Acquisition [Line Items]
Assets, Total			$ 334,869	$ 350,370
Bancshares [Member]
Business Acquisition [Line Items]
Business Combination, Consideration Transferred		$ 41,781
Business Acquisition, Percentage of Voting Interests Acquired		51.00%
Business Acquisition, Equity Interest Issued or Issuable, Number of Shares | shares		1,213,985
Business Acquisition, Percentage of Cash		49.00%
Payments to Acquire Businesses, Gross		$ 20,400
Business Combination, Fair Value Of Assets Acquired		301,499
Loans from merger		202,433
Goodwill		12,254
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Deposits		245,230
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Intangible Assets, Other than Goodwill		$ 2,701
Loans purchased evaluated in conjunction with the acquisition				200,000
Loans purchased evaluated in conjunction with the acquisition, discount				4,500
Loans, purchase credit impaired				7,800
Loans and debt securities acquired with deteriorated credit quality, discount				$ 3,300
Effective tax rate				36.00%
Bancshares [Member] | Oklahoma City [Member]
Business Acquisition [Line Items]
Number of branches acquired | item		5
Bancshares [Member] | Denver [Member]
Business Acquisition [Line Items]
Number of branches acquired | item		3