First Interstate BancSystem (FIBK) 10-Q 1 Aug 14 2014 Q2 Quarterly report Financial data

Document_and_Entity_Informatio

Document and Entity Information	6 Months Ended
	Jun. 30, 2014
Entity Registrant Name	'FIRST INTERSTATE BANCSYSTEM INC
Entity Central Index Key	'0000860413
Current Fiscal Year End Date	'--12-31
Entity Filer Category	'Accelerated Filer
Document Type	'10-Q
Document Period End Date	30-Jun-14
Document Fiscal Year Focus	'2014
Document Fiscal Period Focus	'Q2
Amendment Flag	'false
Class A Common Stock	'
Entity Common Stock, Shares Outstanding	20,269,171
Class B Common Stock	'
Entity Common Stock, Shares Outstanding	23,985,841

Consolidated_Balance_Sheets_Un

Consolidated Balance Sheets (Unaudited) (USD $)	Jun. 30, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Assets	'	'
Cash and due from banks	$168,600	$141,663
Federal funds sold	3,512	672
Interest bearing deposits in banks	331,536	392,492
Total cash and cash equivalents	503,648	534,827
Investment securities:	'	'
Available-for-sale	1,506,996	1,947,706
Held-to-maturity (estimated fair values of $592,682 and $205,926 at June 30, 2014 and December 31, 2013, respectively)	586,989	203,837
Total investment securities	2,093,985	2,151,543
Loans held for investment	4,449,699	4,303,992
Mortgage loans held for sale	56,663	40,861
Total loans	4,506,362	4,344,853
Less allowance for loan losses	78,266	85,339
Net loans	4,428,096	4,259,514
Goodwill	183,673	183,673
Premises and equipment, net of accumulated depreciation	180,341	179,690
Company-owned life insurance	138,899	122,175
Other real estate owned (OREO)	16,425	15,504
Accrued interest receivable	26,497	26,450
Mortgage servicing rights, net of accumulated amortization and impairment reserve	13,443	13,546
Deferred tax asset, net	0	12,154
Core deposit intangibles, net of accumulated amortization	3,811	4,519
Other assets	62,561	61,056
Total assets	7,651,379	7,564,651
Deposits:	'	'
Non-interest bearing	1,533,484	1,491,683
Interest bearing	4,645,558	4,642,067
Total deposits	6,179,042	6,133,750
Securities sold under repurchase agreements	462,985	457,437
Accounts payable and accrued expenses	42,693	47,523
Accrued interest payable	5,316	4,963
Deferred tax liability	3,427	0
Long-term debt	36,893	36,917
Other borrowed funds	20	3
Subordinated debentures held by subsidiary trusts	82,477	82,477
Total liabilities	6,812,853	6,763,070
Stockholders' equity:	'	'
Nonvoting noncumulative preferred stock without par value; authorized 100,000 shares; no shares issued and outstanding as of June 30, 2014 or December 31, 2013	0	0
Common stock	283,697	285,535
Retained earnings	560,469	532,087
Accumulated other comprehensive income, net	-5,640	-16,041
Total stockholders' equity	838,526	801,581
Total liabilities and stockholders' equity	$7,651,379	$7,564,651

Consolidated_Balance_Sheets_Un1

Consolidated Balance Sheets (Unaudited) (Parenthetical) (USD $)	Jun. 30, 2014	Dec. 31, 2013
In Thousands, except Share data, unless otherwise specified
Investment securities:	'	'
Held-to-Maturity, Estimated Fair Value	$592,682	$205,926
Stockholders' equity:	'	'
Nonvoting noncumulative preferred stock, par value	$0	$0
Nonvoting noncumulative preferred stock, authorized shares	100,000	100,000
Nonvoting noncumulative preferred stock, issued shares	0	0
Nonvoting noncumulative preferred stock, outstanding shares	0	0

Consolidated_Statements_of_Inc

Consolidated Statements of Income (Unaudited) (USD $)	3 Months Ended		6 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Interest income:	'	'	'	'
Interest and fees on loans	$55,565	$54,853	$109,283	$110,346
Interest and dividends on investment securities:	'	'	'	'
Taxable	7,309	7,671	14,949	15,717
Exempt from federal taxes	1,083	1,215	2,180	2,441
Interest on deposits in banks	225	212	456	510
Interest on federal funds sold	3	5	4	9
Total interest income	64,185	63,956	126,872	129,023
Interest expense:	'	'	'	'
Interest on deposits	3,327	4,038	6,751	8,393
Interest on securities sold under repurchase agreements	63	74	129	174
Interest on long-term debt	476	483	949	963
Interest on preferred stock pending redemption	0	0	0	159
Interest on subordinated debentures held by subsidiary trusts	592	601	1,180	1,297
Total interest expense	4,458	5,196	9,009	10,986
Net interest income	59,727	58,760	117,863	118,037
Provision for loan losses	-2,001	375	-7,001	875
Net interest income after provision for loan losses	61,728	58,385	124,864	117,162
Non-interest income:	'	'	'	'
Other service charges, commissions and fees	9,699	8,977	18,855	17,233
Income from the origination and sale of loans	6,380	10,043	11,040	20,718
Investment Advisory, Management and Administrative Fees	4,609	4,020	9,064	8,154
Service charges on deposit accounts	3,929	4,323	7,804	8,391
Investment securities gains, net	17	-12	88	-4
Other income	1,937	2,228	3,826	3,906
Total non-interest income	26,571	29,579	50,677	58,398
Non-interest expense:	'	'	'	'
Salaries and wages	24,440	23,535	46,882	46,977
Employee benefits	7,164	7,546	15,477	15,721
Occupancy, net	4,253	4,063	8,492	8,089
Furniture and equipment	3,157	3,163	6,358	6,215
Outsourced technology services	2,309	2,195	4,609	4,352
OREO expense, net of income	-134	-915	-153	981
FDIC insurance premiums	1,093	1,356	2,209	2,733
Professional fees	1,278	1,136	2,648	2,263
Mortgage servicing rights amortization	583	719	1,183	1,558
Mortgage servicing rights impairment recovery	-11	-11	-56	-59
Core deposit intangibles amortization	354	355	708	709
Other expenses	10,837	11,878	21,304	22,166
Non-core acquisition expenses	597	0	597	0
Total non-interest expense	55,920	55,020	110,258	111,705
Income before income tax expense	32,379	32,944	65,283	63,855
Income tax expense	11,302	11,439	22,813	22,306
Net income	$21,077	$21,505	$42,470	$41,549
Basic earnings per common share	$0.48	$0.49	$0.96	$0.96
Diluted earnings per common share	$0.47	$0.49	$0.95	$0.95

Consolidated_Statements_of_Com

Consolidated Statements of Comprehensive Income (USD $)	3 Months Ended		6 Months Ended
In Thousands, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Net income	$21,077	$21,505	$42,470	$41,549
Other comprehensive income (loss), before tax:	'	'	'	'
Change in net unrealized gains (losses) during period	2,816	-35,625	17,167	-41,342
Reclassification adjustment for net gains included in income	-17	12	-88	4
Defined benefit post-retirement benefits plans:	'	'	'	'
Change in net actuarial loss	35	35	70	70
Other comprehensive income (loss), before tax	2,834	-35,578	17,149	-41,268
Deferred tax benefit (expense) related to other comprehensive income	-1,115	13,999	-6,748	16,238
Other comprehensive income (loss), net of tax	1,719	-21,579	10,401	-25,030
Comprehensive income, net of tax	$22,796	($74)	$52,871	$16,519

Consolidated_Statements_of_Cha

Consolidated Statements of Changes in Stockholders Equity (Unaudited) (USD $)	Total	Common stock	Retained earnings	Accumulated other comprehensive income
In Thousands, unless otherwise specified
Beginning Balance at Dec. 31, 2012	$751,186	$271,335	$463,860	$15,991
Comprehensive income:	'	'	'	'
Net income	41,549	0	41,549	0
Other comprehensive income, net of tax	-25,030	0	0	-25,030
Common stock transactions:	'	'	'	'
Common shares purchased and retired 349,930 and 25,677 in 2014 and 2013, respectively	-448	-448	0	0
Common shares issued 24,581 in 2014 and 26,096 in 2013	0	0	0	0
Non-vested common shares issued 147,876 and 108,873 in 2014 and 2013 respectively	0	0	0	0
8,647 and 10,138 non-vested common shares forfeited in 2014 and 2013 respectively	0	0	0	0
286,069 and 446,404 stock options exercised, net of 160,377 and 150,290 shares tendered in payment of option price and income tax withholding amounts in 2014 and 2013 respectively	5,799	5,799	0	0
Tax benefit of stock-based compensation	524	524	0	0
Stock-based compensation expense	2,022	2,022	0	0
Cash dividends declared:	'	'	'	'
Common ($0.32 per share) in 2014 and ($0.13 per share) in 2013	-5,648	0	-5,648	0
Ending Balance at Jun. 30, 2013	769,954	279,232	499,761	-9,039
Beginning Balance at Dec. 31, 2013	801,581	285,535	532,087	-16,041
Comprehensive income:	'	'	'	'
Net income	42,470	0	42,470	0
Other comprehensive income, net of tax	10,401	0	0	10,401
Common stock transactions:	'	'	'	'
Common shares purchased and retired 349,930 and 25,677 in 2014 and 2013, respectively	-8,764	-8,764	0	0
Common shares issued 24,581 in 2014 and 26,096 in 2013	0	0	0	0
Non-vested common shares issued 147,876 and 108,873 in 2014 and 2013 respectively	0	0	0	0
8,647 and 10,138 non-vested common shares forfeited in 2014 and 2013 respectively	0	0	0	0
286,069 and 446,404 stock options exercised, net of 160,377 and 150,290 shares tendered in payment of option price and income tax withholding amounts in 2014 and 2013 respectively	3,547	3,547	0	0
Tax benefit of stock-based compensation	1,225	1,225	0	0
Stock-based compensation expense	2,154	2,154	0	0
Cash dividends declared:	'	'	'	'
Common ($0.32 per share) in 2014 and ($0.13 per share) in 2013	-14,088	0	-14,088	0
Ending Balance at Jun. 30, 2014	$838,526	$283,697	$560,469	($5,640)

Consolidated_Statements_of_Cha1

Consolidated Statements of Changes in Stockholders Equity (Unaudited) (Parenthetical) (USD $)	6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013
Common stock	'	'
Common stock transactions:	'	'
Common shares purchased and retired	349,930	25,677
Common shares issued	24,581	26,096
Non-vested common shares issued	147,876	108,873
Non-vested common shares forfeited	8,647	10,138
Stock options exercised	286,069	446,404
Shares tendered in payment of option price and income tax withholding amounts	160,377	150,290
Retained earnings	'	'
Cash dividends declared:	'	'
Common (in dollars per share)	0.32	0.13

Consolidated_Statements_of_Cas

Consolidated Statements of Cash Flows (Unaudited) (USD $)	6 Months Ended
In Thousands, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013
Cash flows from operating activities:	'	'
Net income	$42,470	$41,549
Adjustments to reconcile net income to net cash provided by operating activities:	'	'
Provision for loan losses	-7,001	875
Net (gain) loss on disposal of property and equipment	-79	-16
Depreciation and amortization	7,786	8,298
Net premium amortization on investment securities	7,088	7,902
Net gains on investment securities transactions	-88	4
Net gains on sales of mortgage loans held for sale	-7,601	-14,984
Net gain on sale of OREO	-766	-2,671
OREO valuation adjustments	10	3,180
Net impairment (reversal of impairment) of mortgage servicing rights	-56	-59
Deferred income tax expense	3,760	3,456
Net increase in cash surrender value of company-owned life insurance policies	-1,724	-873
Stock-based compensation expense	2,154	2,022
Tax benefits from stock-based compensation expense	1,225	524
Excess tax benefits from stock-based compensation	-1,211	-468
Originations of loans held for sale	-412,050	-734,657
Proceeds from sales of loans held for sale	402,825	739,648
Changes in operating assets and liabilities:	'	'
Increase in interest receivable	-47	-403
Decrease in other assets	-1,929	7,004
Decrease in accrued interest payable	353	-266
Decrease in accounts payable and accrued expenses	-4,788	-4,112
Net cash provided by operating activities	30,331	55,953
Cash flows from investing activities:	'	'
Purchases of held-to-maturity investment securities	-4,141	-13,755
Purchases of available-for-sale investment securities	-175,823	-430,395
Proceeds from maturities and paydowns of held-to-maturity investment securities	9,347	5,807
Proceeds from maturities and paydowns of available-for-sale investment securities	243,355	453,678
Purchases of company-owned life insurance	-15,000	0
Proceeds from sales of mortgage servicing rights	266	470
Extensions of credit to customers, net of repayments	-155,523	-84,078
Recoveries of loans charged-off	5,345	7,057
Proceeds from sales of OREO	4,234	18,464
Capital contribution to unconsolidated equity method investee	-6,309	-1,886
Net cash used in investing activities	-94,249	-44,638
Cash flows from financing activities:	'	'
Net increase (decrease) in deposits	45,292	-310,079
Net decrease in repurchase agreements	5,548	-84,471
Net increase (decrease) in short-term borrowings	17	-30
Repayments of long-term debt	-24	-21
Redemption of preferred stock	0	-50,000
Proceeds from issuance of common stock	3,547	5,799
Excess tax benefits from stock-based compensation	1,211	468
Purchase and retirement of common stock	-8,764	-448
Dividends paid to common stockholders	-14,088	-5,648
Net cash provided by (used in) financing activities	32,739	-444,430
Net increase (decrease) in cash and cash equivalents	-31,179	-433,115
Cash and cash equivalents at beginning of period	534,827	801,332
Cash and cash equivalents at end of period	503,648	368,217
Supplemental disclosures of cash flow information:	'	'
Cash paid during the period for income taxes	16,190	20,838
Cash paid during the period for interest expense	$8,656	$11,252

Basis_of_Presentation

Basis of Presentation	6 Months Ended
	Jun. 30, 2014
Organization, Consolidation and Presentation of Financial Statements [Abstract]	'
Basis of Presentation	'
	Basis of Presentation
	In the opinion of management, the accompanying unaudited consolidated financial statements of First Interstate BancSystem, Inc. and subsidiaries (the “Company”) contain all adjustments (all of which are of a normal recurring nature) necessary to present fairly the financial position of the Company at June 30, 2014 and December 31, 2013, and the results of operations for each of the three and six month periods ended and cash flows for each of the six month periods ended June 30, 2014 and 2013 in conformity with U.S. generally accepted accounting principles. The balance sheet information at December 31, 2013 is derived from audited consolidated financial statements. Certain reclassifications, none of which were material, have been made to conform prior year financial statements to the June 30, 2014 presentation. These reclassifications did not change previously reported net income or stockholders’ equity.
	These unaudited consolidated financial statements should be read in conjunction with the audited consolidated financial statements and related notes included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2013. Operating results for the three and six months ended June 30, 2014 are not necessarily indicative of the results that may be expected for the year ending December 31, 2014.

Investment_Securities

Investment Securities	6 Months Ended
	Jun. 30, 2014
Investments, Debt and Equity Securities [Abstract]	'
Investment Securities	'
	Investment Securities
	The amortized cost and approximate fair values of investment securities are summarized as follows:
	June 30, 2014	Amortized		Gross			Gross			Estimated
		Cost		Unrealized			Unrealized			Fair
				Gains			Losses			Value
	Available-for-Sale:
	Obligations of U.S. government agencies	$	722,034	$	1,707		$	(5,174	)	$	718,567
	U.S. agency residential mortgage-backed securities & collateralized mortgage obligations	778,641		12,806			(3,383		)	788,064
	Private mortgage-backed securities	361		6			(2		)	365
	Total	$	1,501,036	$	14,519		$	(8,559	)	$	1,506,996
	June 30, 2014	Amortized		Gross			Gross			Estimated
		Cost		Unrealized			Unrealized			Fair
				Gains			Losses			Value
	Held-to-Maturity:
	State, county and municipal securities	$	179,131	$	6,159		$	(600	)	$	184,690
	Corporate securities	17,908		116			—			18,024
	U.S agency residential mortgage-backed securities &	389,950		18			—			389,968
	collateralized mortgage obligations
	Total	$	586,989	$	6,293		$	(600	)	$	592,682
	December 31, 2013	Amortized		Gross			Gross			Estimated
		Cost		Unrealized			Unrealized			Fair
				Gains			Losses			Value
	Available-for-Sale:
	Obligations of U.S. government agencies	$	774,055	$	1,432		$	(12,249	)	$	763,238
	U.S. agency residential mortgage-backed securities & collateralized mortgage obligations	1,197,295		11,905			(25,147		)	1,184,053
	Private mortgage-backed securities	407		9			(1		)	415
	Total	$	1,971,757	$	13,346		$	(37,397	)	$	1,947,706
	December 31, 2013	Amortized		Gross			Gross			Estimated
		Cost		Unrealized			Unrealized			Fair
				Gains			Losses			Value
	Held-to-Maturity:
	State, county and municipal securities	$	185,818	$	4,043		$	(2,049	)	$	187,812
	Corporate securities	18,019		103			(8		)	18,114
	Total	$	203,837	$	4,146		$	(2,057	)	$	205,926
	Gross realized gains and losses from the disposition of investment securities are summarized in the following table:
		Three Months Ended June 30,							Six Months Ended June 30,
		2014			2013				2014				2013
	Gross realized gains	$	18		$	4			$	243			$	12
	Gross realized losses	1			16				155				16
	On June 27, 2014, the Company transferred available-for-sale U.S. agency residential mortgage-backed securities and collateralized mortgage obligations with amortized costs and fair values of $396,640 and $388,808, respectively, into the held-to-maturity category. Unrealized net losses of $7,832 included in accumulated other comprehensive income at the time of the transfer are being amortized to yield over the remaining expected lives of the transferred securities of 4.3 years.
	The following tables show the gross unrealized losses and fair values of investment securities, aggregated by investment category, and the length of time individual investment securities have been in a continuous unrealized loss position, as of June 30, 2014 and December 31, 2013.
		Less than 12 Months						12 Months or More							Total
	June 30, 2014	Fair		Gross				Fair			Gross				Fair		Gross
		Value		Unrealized				Value			Unrealized				Value		Unrealized
				Losses							Losses						Losses
	Available-for-Sale:
	Obligations of U.S. government agencies	$	61,265	$	(185	)		$	353,997		$	(4,989	)		$	415,262	$	(5,174	)
	U.S. agency residential mortgage-backed securities & collateralized mortgage obligations	47,884		(146		)		203,157			(3,237		)		251,041		(3,383		)
	Private mortgage-backed securities	—		—				95			(2		)		95		(2		)
	Total	$	109,149	$	(331	)		$	557,249		$	(8,228	)		$	666,398	$	(8,559	)
		Less than 12 Months						12 Months or More							Total
	June 30, 2014	Fair		Gross				Fair			Gross				Fair		Gross
		Value		Unrealized				Value			Unrealized				Value		Unrealized
				Losses							Losses						Losses
	Held-to-Maturity:
	State, county and municipal securities	$	267	$	(1	)		$	28,986		$	(599	)		$	29,253	$	(600	)
	Total	$	267	$	(1	)		$	28,986		$	(599	)		$	29,253	$	(600	)
		Less than 12 Months						12 Months or More							Total
	December 31, 2013	Fair		Gross				Fair			Gross				Fair		Gross
		Value		Unrealized				Value			Unrealized				Value		Unrealized
				Losses							Losses						Losses
	Available-for-Sale:
	Obligations of U.S. government agencies	$	458,385	$	(10,355	)		$	59,362		$	(1,894	)		$	517,747	$	(12,249	)
U.S. agency residential mortgage-backed securities & collateralized mortgage obligations	634,199		(17,273		)		166,930			(7,874		)		801,129		(25,147		)
Private mortgage-backed securities	—		—				104			(1		)		104		(1		)
Total	$	1,092,584	$	(27,628	)		$	226,396		$	(9,769	)		$	1,318,980	$	(37,397	)
	Less than 12 Months						12 Months or More							Total
December 31, 2013	Fair		Gross				Fair			Gross				Fair		Gross
	Value		Unrealized				Value			Unrealized				Value		Unrealized
			Losses							Losses						Losses
Held-to-Maturity:
State, county and municipal securities	$	37,550	$	(1,319	)		$	14,296		$	(730	)		$	51,846	$	(2,049	)
Corporate securities	7,294		(8		)		—			—				7,294		(8		)
Total	$	44,844	$	(1,327	)		$	14,296		$	(730	)		$	59,140	$	(2,057	)
The investment portfolio is evaluated quarterly for other-than-temporary declines in the market value of each individual investment security. The Company had 106 and 229 individual investment securities that were in an unrealized loss position as of June 30, 2014 and December 31, 2013, respectively. Unrealized losses as of June 30, 2014 and December 31, 2013 related primarily to fluctuations in the current interest rates. The Company does not have the intent to sell any of the available-for-sale securities in the above table and it is not likely that the Company will have to sell any such securities before a recovery in cost. No impairment losses were recorded during the three and six months ended June 30, 2014 and 2013.
Maturities of investment securities at June 30, 2014 are shown below. Maturities of mortgage-backed securities have been adjusted to reflect shorter maturities based upon estimated prepayments of principal. All other investment securities maturities are shown at contractual maturity dates.
	Available-for-Sale						Held-to-Maturity
June 30, 2014	Amortized		Estimated				Amortized			Estimated
	Cost		Fair Value				Cost			Fair Value
Within one year	$	235,880	$	238,377			$	75,137		$	75,805
After one year but within five years	1,046,202		1,050,653				262,721			265,277
After five years but within ten years	203,374		202,197				174,980			176,267
After ten years	15,580		15,769				74,151			75,333
Total	$	1,501,036	$	1,506,996			$	586,989		$	592,682
As of June 30, 2014, the Company had investment securities callable within one year with amortized costs and estimated fair values of $208,708 and $208,188, respectively, including callable structured notes with amortized costs and estimated fair values of $94,473 and $94,487, respectively. These investment securities are primarily classified as available-for-sale and included in the after one year but within five years category in the table above.

Loans

Loans	6 Months Ended
	Jun. 30, 2014
Receivables [Abstract]	'
Loans	'
	Loans
	The following table presents loans by class as of the dates indicated:
		June 30,				December 31,
		2014				2013
	Real estate loans:
	Commercial	$	1,464,947			$	1,449,174
	Construction:
	Land acquisition & development	192,289				205,911
	Residential	82,121				76,488
	Commercial	86,599				69,236
	Total construction loans	361,009				351,635
	Residential	894,502				867,912
	Agricultural	162,428				173,534
	Total real estate loans	2,882,886				2,842,255
	Consumer:
	Indirect consumer	512,063				476,012
	Other consumer	133,604				133,039
	Credit card	61,368				62,536
	Total consumer loans	707,035				671,587
	Commercial	727,482				676,544
	Agricultural	130,280				111,872
	Other, including overdrafts	2,016				1,734
	Loans held for investment	4,449,699				4,303,992
	Mortgage loans held for sale	56,663				40,861
	Total loans	$	4,506,362			$	4,344,853
	Loans are considered past due if the required principal and interest payments have not been received as of the date such payments were due. The following tables present the contractual aging of the Company’s recorded investment in past due loans by class as of the dates indicated:
											Total Loans
		30 - 59			60 - 89			> 90			30 or More
		Days			Days			Days			Days		Current		Non-accrual		Total
	As of June 30, 2014	Past Due			Past Due			Past Due			Past Due		Loans		Loans		Loans
	Real estate
	Commercial	$	5,343		$	2,540		$	40		$	7,923	$	1,418,602	$	38,422	$	1,464,947
	Construction:
	Land acquisition & development	782			123			—			905		180,094		11,290		192,289
	Residential	90			1,226			—			1,316		80,152		653		82,121
	Commercial	—			—			—			—		84,019		2,580		86,599
	Total construction loans	872			1,349			—			2,221		344,265		14,523		361,009
	Residential	3,493			823			665			4,981		884,261		5,260		894,502
	Agricultural	29			72			—			101		155,228		7,099		162,428
	Total real estate loans	9,737			4,784			705			15,226		2,802,356		65,304		2,882,886
	Consumer:
	Indirect consumer	2,467			404			15			2,886		508,777		400		512,063
	Other consumer	780			210			16			1,006		131,864		734		133,604
	Credit card	281			239			335			855		60,496		17		61,368
	Total consumer loans	3,528			853			366			4,747		701,137		1,151		707,035
	Commercial	3,223			718			325			4,266		710,886		12,330		727,482
	Agricultural	1,390			17			125			1,532		128,367		381		130,280
	Other, including overdrafts	—			—			1			1		2,015		—		2,016
	Loans held for investment	17,878			6,372			1,522			25,772		4,344,761		79,166		4,449,699
	Mortgage loans originated for sale	—			—			—			—		56,663		—		56,663
	Total loans	$	17,878		$	6,372		$	1,522		$	25,772	$	4,401,424	$	79,166	$	4,506,362
											Total Loans
		30 - 59			60 - 89			> 90			30 or More
		Days			Days			Days			Days		Current		Non-accrual		Total
	As of December 31, 2013	Past Due			Past Due			Past Due			Past Due		Loans		Loans		Loans
	Real estate
	Commercial	$	5,924		$	2,472		$	22		$	8,418	$	1,391,823	$	48,933	$	1,449,174
	Construction:
	Land acquisition & development	1,062			468			38			1,568		188,074		16,269		205,911
	Residential	933			250			—			1,183		73,933		1,372		76,488
	Commercial	584			—			—			584		68,427		225		69,236
	Total construction loans	2,579			718			38			3,335		330,434		17,866		351,635
	Residential	3,630			206			1,162			4,998		856,800		6,114		867,912
Agricultural	328			646			—			974		163,986		8,574		173,534
Total real estate loans	12,461			4,042			1,222			17,725		2,743,043		81,487		2,842,255
Consumer:
Indirect consumer	3,303			430			9			3,742		471,906		364		476,012
Other consumer	925			130			1			1,056		131,508		475		133,039
Credit card	364			187			515			1,066		61,451		19		62,536
Total consumer loans	4,592			747			525			5,864		664,865		858		671,587
Commercial	2,791			1,186			563			4,540		660,035		11,969		676,544
Agricultural	453			672			—			1,125		110,622		125		111,872
Other, including overdrafts	—			—			—			—		1,734		—		1,734
Loans held for investment	20,297			6,647			2,310			29,254		4,180,299		94,439		4,303,992
Mortgage loans originated for sale	—			—			—			—		40,861		—		40,861
Total loans	$	20,297		$	6,647		$	2,310		$	29,254	$	4,221,160	$	94,439	$	4,344,853
If interest on non-accrual loans had been accrued, such income would have been approximately $1,061 and $1,299 for the three months ended June 30, 2014 and 2013, respectively, and approximately $2,182 and $2,651 for the six months ended June 30, 2014 and 2013, respectively.
The Company considers impaired loans to include all loans risk rated doubtful, loans placed on non-accrual status and loans renegotiated in troubled debt restructurings with the exception of consumer loans. The following tables present information on the Company’s recorded investment in impaired loans as of dates indicated:
As of June 30, 2014	Unpaid			Recorded			Recorded			Total		Related
	Total			Investment			Investment			Recorded		Allowance
	Principal			With No			With			Investment
	Balance			Allowance			Allowance
Real estate:
Commercial	$	52,690		$	24,961		$	25,622		$	50,583	$	3,566
Construction:
Land acquisition & development	15,601			8,098			3,869			11,967		647
Residential	1,096			653			—			653		—
Commercial	2,749			269			2,446			2,715		908
Total construction loans	19,446			9,020			6,315			15,335		1,555
Residential	7,222			4,885			375			5,260		301
Agricultural	9,191			6,656			2,439			9,095		133
Total real estate loans	88,549			45,522			34,751			80,273		5,555
Commercial	14,752			10,709			2,679			13,388		1,176
Agricultural	792			419			322			741		221
Total	$	104,093		$	56,650		$	37,752		$	94,402	$	6,952
As of December 31, 2013	Unpaid			Recorded			Recorded			Total		Related
	Total			Investment			Investment			Recorded		Allowance
	Principal			With No			With			Investment
	Balance			Allowance			Allowance
Real estate:
Commercial	$	64,780		$	29,216		$	33,937		$	63,153	$	5,210
Construction:
Land acquisition & development	23,906			9,901			7,226			17,127		1,434
Residential	1,816			1,095			277			1,372		26
Commercial	397			279			84			363		85
Total construction loans	26,119			11,275			7,587			18,862		1,545
Residential	9,448			5,081			967			6,048		249
Agricultural	8,895			6,429			2,370			8,799		335
Total real estate loans	109,242			52,001			44,861			96,862		7,339
Commercial	15,448			10,684			2,901			13,585		1,504
Agricultural	177			39			86			125		86
Total	$	124,867		$	62,724		$	47,848		$	110,572	$	8,929
The following tables present the average recorded investment in and income recognized on impaired loans for the periods indicated:
	Three Months Ended June 30,
	2014								2013
	Average Recorded Investment				Income Recognized				Average Recorded Investment			Income Recognized
Real estate:
Commercial	$	57,588			$	241			$	67,605		$	272
Construction:
Land acquisition & development	13,563				11				19,007			15
Residential	785				—				1,569			—
Commercial	1,471				2				6,346			—
Total construction loans	15,819				13				26,922			15
Residential	5,852				1				8,311			5
Agricultural	9,747				25				8,255			4
Total real estate loans	89,006				280				111,093			296
Commercial	14,162				14				16,087			18
Agricultural	742				6				373			4
Total	$	103,910			$	300			$	127,553		$	318
	Six Months Ended June 30,
	2014								2013
	Average Recorded Investment				Income Recognized				Average Recorded Investment			Income Recognized
Real estate:
Commercial	$	60,870			$	457			$	67,192		$	610
Construction:
Land acquisition & development	14,554				22				20,123			456
Residential	1,051				—				2,040			—
Commercial	918				4				7,118			—
Total construction loans	16,523				26				29,281			456
Residential	5,969				3				9,429			9
Agricultural	9,830				29				6,611			8
Total real estate loans	93,192				515				112,513			1,083
Commercial	14,231				28				14,484			36
Agricultural	538				12				502			8
Total	$	107,961			$	555			$	127,499		$	1,127
The amount of interest income recognized by the Company within the period that the loans were impaired was primarily related to loans modified in a troubled debt restructuring that remained on accrual status. Interest payments received on non-accrual impaired loans are applied to principal. Interest income is subsequently recognized only to the extent cash payments are received in excess of principal due. If interest on impaired loans had been accrued, interest income on impaired loans would have been approximately $1,301 and $1,577 for the three months ended June 30, 2014 and 2013, respectively and approximately $2,412 and $2,912 for the six months ended June 30, 2014 and 2013, respectively.
Collateralized impaired loans are generally recorded at the fair value of the underlying collateral using discounted cash flows, independent appraisals and management estimates based upon current market conditions. For loans measured under the present value of cash flows method, the change in present value attributable to the passage of time, if applicable, is recognized in the provision for loan losses and thus no interest income is recognized.
Modifications of performing loans are made in the ordinary course of business and are completed on a case-by-case basis as negotiated with the borrower. Loan modifications typically include interest rate concessions, interest only periods of less than twelve months, short-term payment deferrals and extension of amortization periods to provide payment relief. A loan modification is considered a troubled debt restructuring if the borrower is experiencing financial difficulties and the Company, for economic or legal reasons, grants a concession to the borrower that it would not otherwise consider. Certain troubled debt restructurings are on non-accrual status at the time of restructuring and are typically returned to accrual status after considering the borrower's sustained repayment performance in accordance with the restructuring agreement for a period of at least six months and management is reasonably assured of future performance. If the troubled debt restructuring meets these performance criteria and the interest rate granted at the modification is equal to or greater than the rate that the Company was willing to accept at the time of the restructuring for a new loan with comparable risk, then the loan will return to performing status and the accrual of interest will resume.
The Company had loans renegotiated in troubled debt restructurings of $57,835 as of June 30, 2014, of which $34,304 were included in non-accrual loans and $23,531 were on accrual status. The Company had loans renegotiated in troubled debt restructurings of $59,792 as of December 31, 2013, of which $38,011 were included in non-accrual loans and $21,781 were on accrual status.
The following tables present information on the Company's troubled debt restructurings that occurred during the three months ended June 30, 2014:
		Number of Notes		Type of Concession										Principal Balance at Restructure Date
Three Months Ended June 30, 2014				Interest only period			Extension of terms or maturity			Interest rate adjustment		Other (1)
Commercial real estate		4		$	458		$	226		$	—	$	679	$	1,363
Commercial		2		72			—			—		—		72
Total loans restructured during period		6		$	530		$	226		$	—	$	679	$	1,435
(1) Other includes concessions that reduce or defer payments for a specified period of time and/or do not fit into other
designated categories.
		Number of Notes		Type of Concession										Principal Balance at Restructure Date
Six Months Ended June 30, 2014				Interest only period			Extension of terms or maturity			Interest rate adjustment		Other (1)
Commercial real estate		8		$	—		$	226		$	—	$	921	$	1,147
Commercial		4		299			2,931			—		30		3,260
Total loans restructured during period		12		$	299		$	3,157		$	—	$	951	$	4,407
(1) Other includes concessions that reduce or defer payments for a specified period of time and/or do not fit into other
designated categories.
For troubled debt restructurings that were on non-accrual status or otherwise deemed impaired before the modification, a specific reserve may already be recorded. In periods subsequent to modification, the Company continues to evaluate all troubled debt restructurings for possible impairment and recognizes impairment through the allowance. Additionally these loans continue to work their way through the credit cycle through charge-off, pay-off or foreclosure. Financial effects of modifications of troubled debt restructurings may include principal loan forgiveness or other charge-offs directly related to the restructuring. The Company had no charge-offs directly related to modifying troubled debt restructurings during the three or six months ended June 30, 2014 or 2013.
The following table presents information on the Company's trouble debt restructurings during the previous 12 months for which there was a payment default during the periods indicated. The Company considers a payment default to occur on troubled debt restructurings when the loan is 90 days or more past due or was placed on non-accrual status after the modification.
	Three Months Ended June 30, 2014				Six Months Ended June 30, 2014
	Number of Notes		Balance		Number of Notes		Balance
Commercial	2		72		2		72
Total	2		72		2		72
At June 30, 2014, there were no material commitments to lend additional funds to borrowers whose existing loans have been renegotiated or are classified as non-accrual.
As part of the on-going and continuous monitoring of the credit quality of the Company’s loan portfolio, management tracks internally assigned risk classifications of loans. The Company adheres to a Uniform Classification System developed jointly by the various bank regulatory agencies to internally risk rate loans. The Uniform Classification System defines three broad categories of criticized assets, which the Company uses as credit quality indicators:
Other Assets Especially Mentioned — includes loans that exhibit weaknesses in financial condition, loan structure or documentation, which if not promptly corrected, may lead to the development of abnormal risk elements.
Substandard — includes loans that are inadequately protected by the current sound worth and paying capacity of the borrower. Although the primary source of repayment for a Substandard loan is not currently sufficient; collateral or other sources of repayment are sufficient to satisfy the debt. Continuance of a Substandard loan is not warranted unless positive steps are taken to improve the worthiness of the credit.
Doubtful — includes loans that exhibit pronounced weaknesses to a point where collection or liquidation in full, on the basis of currently existing facts, conditions and values, is highly questionable and improbable. Doubtful loans are required to be placed on non-accrual status and are assigned specific loss exposure.
The following tables present the Company’s recorded investment in criticized loans by class and credit quality indicator based on the most recent analysis performed as of the dates indicated:
As of June 30, 2014	Other Assets			Substandard			Doubtful			Total
	Especially									Criticized
	Mentioned									Loans
Real estate:
Commercial	$	81,539		$	82,558		$	15,371		$	179,468
Construction:
Land acquisition & development	12,580			13,053			2,626			28,259
Residential	2,190			1,788			—			3,978
Commercial	186			269			2,446			2,901
Total construction loans	14,956			15,110			5,072			35,138
Residential	11,028			9,017			588			20,633
Agricultural	9,638			15,755			2,439			27,832
Total real estate loans	117,161			122,440			23,470			263,071
Consumer:
Indirect consumer	769			1,575			133			2,477
Other consumer	529			927			398			1,854
Credit card	—			390			1,219			1,609
Total consumer loans	1,298			2,892			1,750			5,940
Commercial	30,522			26,203			3,573			60,298
Agricultural	11,290			4,209			322			15,821
Total	$	160,271		$	155,744		$	29,115		$	345,130
As of December 31, 2013	Other Assets			Substandard			Doubtful			Total
	Especially									Criticized
	Mentioned									Loans
Real estate:
Commercial	$	79,747		$	86,426		$	24,840		$	191,013
Construction:
Land acquisition & development	13,211			19,677			7,329			40,217
Residential	1,859			1,649			277			3,785
Commercial	—			409			84			493
Total construction loans	15,070			21,735			7,690			44,495
Residential	7,500			7,188			4,184			18,872
Agricultural	13,597			10,245			2,370			26,212
Total real estate loans	115,914			125,594			39,084			280,592
Consumer:
Indirect consumer	875			1,524			115			2,514
Other consumer	573			969			268			1,810
Credit card	—			392			2,010			2,402
Total consumer loans	1,448			2,885			2,393			6,726
Commercial	33,318			23,833			3,745			60,896
Agricultural	8,401			1,788			86			10,275
Total	$	159,081		$	154,100		$	45,308		$	358,489
The Company maintains a credit review function, which is independent of the credit approval process, to assess assigned internal risk classifications and monitor compliance with internal lending policies and procedures. Written action plans with firm target dates for resolution of identified problems are maintained and reviewed on a quarterly basis for all categories of criticized loans.

Allowance_For_Loan_Losses

Allowance For Loan Losses	6 Months Ended
	Jun. 30, 2014
Receivables [Abstract]	'
Allowance For Loan Losses	'
	Allowance For Loan Losses
	The following tables present a summary of changes in the allowance for loan losses by portfolio segment for the periods indicated.
	Three Months Ended June 30, 2014	Real Estate			Consumer			Commercial			Agriculture			Other		Total
	Allowance for loan losses:
	Beginning balance	$	59,830		$	5,377		$	15,701		$	463		$	—	$	81,371
	Provision charged to operating expense	(2,011		)	346			(494		)	158			—		(2,001		)
	Less loans charged-off	(1,158		)	(934		)	(534		)	—			—		(2,626		)
	Add back recoveries of loans previously	651			558			313			—			—		1,522
	charged-off
	Ending balance	$	57,312		$	5,347		$	14,986		$	621		$	—	$	78,266
	Six Months Ended June 30, 2014	Real Estate			Consumer			Commercial			Agriculture			Other		Total
	Allowance for loan losses:
	Beginning balance	$	63,923		$	6,193		$	14,747		$	476		$	—	$	85,339
	Provision charged to operating expense	(5,386		)	(232		)	(1,566		)	183			—		(7,001		)
	Less loans charged-off	(2,243		)	(1,780		)	(1,330		)	(64		)	—		(5,417		)
	Add back recoveries of loans previously	1,018			1,166			3,135			26			—		5,345
	charged-off
	Ending balance	$	57,312		$	5,347		$	14,986		$	621		$	—	$	78,266
	As of June 30, 2014	Real Estate			Consumer			Commercial			Agriculture			Other		Total
	Allowance for loan losses:
	Loans individually evaluated for impairment	$	5,555		$	—		$	1,176		$	221		$	—	$	6,952
	Loans collectively evaluated for impairment	51,757			5,347			13,810			400			—		71,314
	Allowance for loan losses	$	57,312		$	5,347		$	14,986		$	621		$	—	$	78,266
	As of June 30, 2014	Real Estate			Consumer			Commercial			Agriculture			Other		Total
	Total loans:
	Individually evaluated for impairment	$	80,273		$	—		$	13,388		$	741		$	—	$	94,402
	Collectively evaluated for impairment	2,859,276			707,035			714,094			129,539			2,016		4,411,960
	Total loans	$	2,939,549		$	707,035		$	727,482		$	130,280		$	2,016	$	4,506,362
	Three Months Ended June 30, 2013	Real Estate			Consumer			Commercial			Agriculture			Other		Total
	Allowance for loan losses:
	Beginning balance	$	71,666		$	7,088		$	18,670		$	480		$	—	$	97,904
	Provision charged to operating expense	(1,009		)	579			778			27			—		375
	Less loans charged-off	(2,027		)	(1,299		)	(569		)	—			—		(3,895		)
	Add back recoveries of loans previously	2,873			672			596			3			—		4,144
	charged-off
	Ending balance	$	71,503		$	7,040		$	19,475		$	510		$	—	$	98,528
	Six Months Ended June 30, 2013	Real Estate			Consumer			Commercial			Agriculture			Other		Total
	Allowance for loan losses:
	Beginning balance	$	75,782		$	7,140		$	17,085		$	504		$	—	$	100,511
	Provision charged to operating expense	(2,044		)	1,116			1,799			4			—		875
	Less loans charged-off	(6,170		)	(2,361		)	(1,380		)	(4		)	—		(9,915		)
	Add back recoveries of loans previously	3,935			1,145			1,971			6			—		7,057
	charged-off
	Ending balance	$	71,503		$	7,040		$	19,475		$	510		$	—	$	98,528
	As of June 30, 2013	Real Estate			Consumer			Commercial			Agriculture			Other		Total
	Allowance for loan losses:
	Loans individually evaluated for impairment	$	10,267		$	—		$	5,205		$	22		$	—	$	15,494
	Loans collectively evaluated for impairment	61,236			7,040			14,270			488			—		83,034
	Allowance for loan losses	$	71,503		$	7,040		$	19,475		$	510		$	—	$	98,528
	As of June 30, 2013	Real Estate			Consumer			Commercial			Agriculture			Other		Total
	Total loans:
	Individually evaluated for impairment	$	107,241		$	—		$	16,710		$	139		$	—	$	124,090
	Collectively evaluated for impairment	2,732,400			652,944			666,539			121,391			—		4,173,274
	Total loans	$	2,839,641		$	652,944		$	683,249		$	121,530		$	—	$	4,297,364
	The Company performs a quarterly assessment of the adequacy of its allowance for loan losses in accordance with generally accepted accounting principles. The methodology used to assess the adequacy is consistently applied to the Company's loan portfolio and consists of three elements: (1) specific valuation allowances based on probable losses on impaired loans; (2) historical valuation allowances based on loan loss experience for similar loans with similar characteristics and trends; and (3) general valuation allowances determined based on changes in the nature of the loan portfolio, overall portfolio quality, industry concentrations, delinquency trends, general economic conditions and other qualitative risk factors both internal and external to the Company.
	Specific allowances are established for loans where management has determined that probability of a loss exists by analyzing the borrower’s ability to repay amounts owed, collateral deficiencies and any relevant qualitative or economic factors impacting the loan. Historical valuation allowances are determined by applying percentage loss factors to the credit exposures from outstanding loans. For commercial, agricultural and real estate loans, loss factors are applied based on the internal risk classifications of these loans. For consumer loans, loss factors are applied on a portfolio basis. For commercial, agriculture and real estate loans, loss factor percentages are based on a migration analysis of our historical loss experience, designed to account for credit deterioration. For consumer loans, loss factor percentages are based on a one-year loss history. General valuation allowances are determined by evaluating, on a quarterly basis, changes in the nature and volume of the loan portfolio, overall portfolio quality, industry concentrations, current economic and regulatory conditions and the estimated impact of these factors on historical loss rates.

OREO

OREO	6 Months Ended
	Jun. 30, 2014
Repossessed Assets [Abstract]	'
Other Real Estate Owned	'
	Other Real Estate Owned
	Information with respect to the Company's other real estate owned follows:
		Three Months Ended June 30,						Six Months Ended June 30,
		2014			2013			2014			2013
	Beginning balance	$	16,594		$	32,470		$	15,504		$	32,571
	Additions	984			3,224			4,399			8,555
	Capitalized improvements	—			3			—			13
	Valuation adjustments	(10		)	(259		)	(10		)	(2,564		)
	Dispositions	(1,143		)	(12,656		)	(3,468		)	(15,793		)
	Ending balance	$	16,425		$	22,782		$	16,425		$	22,782

Capital_Stock

Capital Stock	6 Months Ended
	Jun. 30, 2014
Equity [Abstract]	'
Common Stock	'
	Capital Stock
	The Company had 20,269,171 shares of Class A common stock and 23,985,841 shares of Class B common stock outstanding as of June 30, 2014. The Company had 19,868,018 shares of Class A common stock and 24,287,045 shares of Class B common stock outstanding as of December 31, 2013.
	During the six months ended June 30, 2014, the Company repurchased and retired 325,418 shares of its Class A common stock in a combination of open market and privately negotiated transactions at an aggregate purchase price of $8,143. The repurchases were made pursuant to a stock repurchase program approved by the Company's Board of Directors in November 2013. Under the terms of the stock repurchase program, the Company may repurchase up to an additional 1,674,582 shares of its Class A common stock prior to expiration of the plan on November 25, 2014. All other stock repurchases during the three and six months ended June 30, 2014 and 2013 were redemptions of vested restricted shares tendered in lieu of cash for payment of income tax withholding amounts by participants of the Company's 2006 Equity Compensation Plan.
	On January 24, 2014, the Company filed a Registration Statement on Form S-8 to register an additional 1,500,000 shares of Class A common stock to be issued pursuant to the Company's 2006 Equity Compensation Plan, as amended and restated.

Earnings_per_Common_Share

Earnings per Common Share	6 Months Ended
	Jun. 30, 2014
Earnings Per Share [Abstract]	'
Earnings per Common Share	'
	Earnings per Common Share
	Basic earnings per common share is calculated by dividing net income by the weighted average number of common shares outstanding during the period presented, excluding unvested restricted stock. Diluted earnings per share is calculated by dividing net income by the weighted average number of common shares determined for the basic earnings per share computation plus the dilutive effects of stock-based compensation using the treasury stock method.
	The following table sets forth the computation of basic and diluted earnings per share for the three and six month periods ended June 30, 2014 and 2013.
		Three Months Ended June 30,				Six Months Ended June 30,
		2014		2013		2014		2013
	Net income	$	21,077	$	21,505	$	42,470	$	41,549
	Weighted average common shares outstanding for basic earnings per share computation	44,044,260		43,480,502		44,021,166		43,335,682
	Dilutive effects of stock-based compensation	531,703		427,785		572,689		376,978
	Weighted average common shares outstanding for diluted earnings per common share computation	44,575,963		43,908,287		44,593,855		43,712,660
	Basic earnings per common share	$	0.48	$	0.49	$	0.96	$	0.96
	Diluted earnings per common share	$	0.47	$	0.49	$	0.95	$	0.95
	The Company had 107,651 and 56,668 shares of unvested restricted stock as of June 30, 2014 and 2013, respectively, that were not included in the computation of diluted earnings per common share because performance conditions for vesting had not been met. In addition, the Company had 976,063 stock options outstanding as of June 30, 2013, that were not included in the computation of diluted earnings per common share because their effect would be anti-dilutive. The Company had no anti-dilutive stock options outstanding as of June 30, 2014.

Regulatory_Capital

Regulatory Capital	6 Months Ended
	Jun. 30, 2014
Banking and Thrift [Abstract]	'
Regulatory Capital	'
	Regulatory Capital
	The Company is subject to the regulatory capital requirements administered by federal banking regulators and the Federal Reserve. Under capital adequacy guidelines and the regulatory framework for prompt corrective action, the Company must meet specific capital guidelines that involve quantitative measures of the Company’s assets, liabilities and certain off-balance sheet items as calculated under regulatory accounting practices. Quantitative measures established by regulation to ensure capital adequacy require the Company to maintain minimum amounts and ratios of total and tier 1 capital to risk-weighted assets, and of tier 1 capital to average assets, as defined in the regulations. As of June 30, 2014 and December 31, 2013, the Company exceeded all capital adequacy requirements to which it is subject.
	Actual capital amounts and ratios and selected minimum regulatory thresholds for the Company and its bank subsidiary, First Interstate Bank (“FIB”), as of June 30, 2014 and December 31, 2013 are presented in the following tables:
		Actual				Adequately Capitalized				Well Capitalized
		Amount		Ratio		Amount		Ratio		Amount		Ratio
	June 30, 2014
	Total risk-based capital:
	Consolidated	$	850,614	16.7	%	$	407,804	8	%	NA		NA
	FIB	740,815		14.6		406,334		8		$	507,917	10	%
	Tier 1 risk-based capital:
	Consolidated	765,715		15		203,902		4		NA		NA
	FIB	668,143		13.2		203,167		4		$	304,750	6
	Leverage capital ratio:
	Consolidated	765,715		10.4		295,843		4		NA		NA
	FIB	668,143		9.1		295,201		4		$	369,002	5
		Actual				Adequately Capitalized				Well Capitalized
		Amount		Ratio		Amount		Ratio		Amount		Ratio
	December 31, 2013
	Total risk-based capital:
	Consolidated	$	829,443	16.8	%	$	396,210	8	%	NA		NA
	FIB	723,955		14.7		394,038		8		$	492,548	10	%
	Tier 1 risk-based capital:
	Consolidated	739,246		14.9		198,105		4		NA		NA
	FIB	650,093		13.2		197,019		4		$	295,529	6
	Leverage capital ratio:
	Consolidated	739,246		10.1		293,414		4		NA		NA
	FIB	650,093		8.9		292,199		4		$	365,248	5

Commitments_and_Contingencies

Commitments and Contingencies	6 Months Ended
	Jun. 30, 2014
Commitments and Contingencies Disclosure [Abstract]	'
Commitments and Contingencies	'
	Commitments and Contingencies
	In the normal course of business, the Company is involved in various claims and litigation. In the opinion of management, following consultation with legal counsel, the ultimate liability or disposition thereof is not expected to have a material adverse effect on the consolidated financial condition, results of operations or liquidity of the Company.
	The Company had commitments under construction agreements of $1,409 as of June 30, 2014.

Financial_Instruments_with_Off

Financial Instruments with Off-Balance Sheet Risk	6 Months Ended
	Jun. 30, 2014
Financial Instruments with Off-Balance Sheet Risk [Abstract]	'
Financial Instruments with Off-Balance Sheet Risk	'
	Financial Instruments with Off-Balance Sheet Risk
	The Company is a party to financial instruments with off-balance sheet risk in the normal course of business to meet the financing needs of its customers. These financial instruments include commitments to extend credit and standby letters of credit. Commitments to extend credit are agreements to lend to a customer as long as there is no violation of any condition established in the commitment contract. Since many of the commitments are expected to expire without being drawn upon, the total commitment amounts do not necessarily represent future cash requirements. At June 30, 2014, commitments to extend credit to existing and new borrowers approximated $1,346,196, which included $447,827 on unused credit card lines and $334,981 with commitment maturities beyond one year.
	Standby letters of credit are conditional commitments issued by the Company to guarantee the performance of a customer to a third party. At June 30, 2014, the Company had outstanding standby letters of credit of $65,133. The estimated fair value of the obligation undertaken by the Company in issuing the standby letters of credit is included in other liabilities in the Company’s consolidated balance sheet.

Supplemental_Disclosures_to_Co

Supplemental Disclosures to Consolidated Statement of Cash Flows	6 Months Ended
	Jun. 30, 2014
Supplemental Cash Flow Information [Abstract]	'
Supplemental Disclosures to Consolidated Statement of Cash Flows	'
	Supplemental Disclosures to Consolidated Statement of Cash Flows
	The Company transferred loans of $4,399 and $8,555 to OREO during the six months ended June 30, 2014 and 2013, respectively.
	The Company transferred internally originated mortgage servicing rights of $1,024 and $2,149 from loans to mortgage servicing assets during the six months ended June 30, 2014 and 2013, respectively.
	The Company reclassified tax credit investments with a carrying value of $429 from held-to-maturity investment securities to other assets during the six months ended June 30, 2013.
	The Company transferred bank buildings and land pending disposal with book values of $1,448 to other assets during the six months ended June 30, 2013.

Other_Comprehensive_Income

Other Comprehensive Income	6 Months Ended
	Jun. 30, 2014
Equity [Abstract]	'
Other Comprehensive Income	'
	Other Comprehensive Income/Loss
	The gross amounts of each component of other comprehensive income (loss) and the related tax effects are as follows:
		Pre-tax						Tax Expense (Benefit)						Net of Tax
	Three Months Ended June 30,	2014			2013			2014			2013			2014			2013
	Investment securities available-for sale:
	Change in net unrealized gains/losses	$	2,816		$	(35,625	)	$	1,108		$	(14,018	)	$	1,708		$	(21,607	)
	during period
	Reclassification adjustment for net (gains)	(17		)	12			(7		)	5			(10		)	7
	losses included in net income
	Defined benefits post-retirement benefit plan:
	Change in net actuarial loss	35			35			14			14			21			21
	Total other comprehensive income (loss)	$	2,834		$	(35,578	)	$	1,115		$	(13,999	)	$	1,719		$	(21,579	)
		Pre-tax						Tax Expense (Benefit)						Net of Tax
	Six Months Ended June 30,	2014			2013			2014			2013			2014			2013
	Investment securities available-for sale:
	Change in net unrealized gains/losses	$	17,167		$	(41,342	)	$	6,755		$	(16,268	)	$	10,412		$	(25,074	)
	during period
	Reclassification adjustment for net (gains)	(88		)	4			(35		)	2			(53		)	2
	losses included in net income
	Defined benefits post-retirement benefit plan:
	Change in net actuarial loss	70			70			28			28			42			42
	Total other comprehensive (loss) income	$	17,149		$	(41,268	)	$	6,748		$	(16,238	)	$	10,401		$	(25,030	)
	The components of accumulated other comprehensive loss, net of income tax benefits, are as follows:
		June 30,			December 31,
		2014			2013
	Net unrealized gain on investment securities available-for-sale	$	(4,219	)	$	(14,578	)
	Net actuarial loss on defined benefit post-retirement benefit plans	(1,421		)	(1,463		)
	Net accumulated other comprehensive loss	$	(5,640	)	$	(16,041	)

Fair_Value_Measurements

Fair Value Measurements	6 Months Ended
	Jun. 30, 2014
Fair Value Disclosures [Abstract]	'
Fair Value Measurements	'
	Fair Value Measurements
	Financial assets and financial liabilities measured at fair value on a recurring basis are as follows:
				Fair Value Measurements at Reporting Date Using
	As of June 30, 2014	Balance		Quoted Prices in		Significant Other			Significant
				Active Markets for		Observable			Unobservable
				Identical Assets		Inputs			Inputs
				(Level 1)		(Level 2)			(Level 3)
	Investment securities available-for-sale:
	Obligations of U.S. government agencies	$	718,567	$	—	$	718,567		$	—
	U.S. agencies mortgage-backed securities & collateralized mortgage obligations	788,064			—	788,064				—
	Private mortgage-backed securities	365			—	365				—
	Mortgage servicing rights	25,812			—	25,812				—
				Fair Value Measurements at Reporting Date Using
	As of December 31, 2013	Balance		Quoted Prices in		Significant Other			Significant
				Active Markets for		Observable			Unobservable
				Identical Assets		Inputs			Inputs
				(Level 1)		(Level 2)			(Level 3)
	Investment securities available-for-sale:
	Obligations of U.S. government agencies	$	763,238	$	—	$	763,238		$	—
	U.S. agencies mortgage-backed securities & collateralized mortgage obligations	1,184,053			—	1,184,053				—
	Private mortgage-backed securities	415			—	415				—
	Mortgage servicing rights	25,698			—	25,698				—
	There were no changes in valuation methodologies or transfers between levels of the fair value hierarchy during the six months ended June 30, 2014 or 2013.
	The methodologies used by the Company in determining the fair values of each class of financial instruments are based primarily on the use of independent, market-based data to reflect a value that would be reasonably expected in an orderly transaction between market participants at the measurement date. The Company obtains fair value measurements for investment securities from an independent pricing service and evaluates mortgage servicing rights for impairment using an independent valuation service. The vendors chosen by the Company are widely recognized vendors whose evaluations support the pricing functions of financial institutions, investment and mutual funds, and portfolio managers. The Company has documented and evaluated the pricing methodologies used by the vendors and maintains internal processes that regularly test valuations. These internal processes include obtaining and reviewing available reports on internal controls, evaluating the prices for reasonableness given market changes, obtaining and evaluating the inputs used in the model for a sample of securities, investigating anomalies and confirming determinations through discussions with the vendor. For investment securities, if needed, a broker may be utilized to determine the reported fair value. Further details on the methods used to estimate the fair value of each class of financial instruments above are discussed below.
	Investment Securities Available-for-Sale. The fair value measurements consider observable data that may include dealer quotes, market spreads, cash flows, the U.S. Treasury yield curve, live trading levels, trade execution data, market consensus prepayment speeds, credit information and the investment's terms and conditions, among other things.
	Mortgage Servicing Rights. Mortgage servicing rights are initially recorded at fair value based on comparable market quotes and are amortized in proportion to and over the period of estimated net servicing income. Mortgage servicing rights are evaluated quarterly for impairment using an independent valuation service. The valuation service utilizes discounted cash flow modeling techniques, which consider observable data that includes market consensus prepayment speeds and the predominant risk characteristics of the underlying loans including loan type, note rate and loan term. Management believes the significant inputs utilized in the valuation model are observable in the market.
	Additionally, from time to time, certain assets are measured at fair value on a non-recurring basis. Adjustments to fair value generally result from the application of lower-of-cost-or-market accounting or write-downs of individual assets due to impairment.
	The following table presents information about the Company’s assets and liabilities measured at fair value on a non-recurring basis.
					Fair Value Measurements at Reporting Date Using
	As of June 30, 2014	Balance		Quoted Prices in		Significant Other		Significant
				Active Markets for		Observable		Unobservable
				Identical Assets		Inputs		Inputs
				(Level 1)		(Level 2)		(Level 3)
	Impaired loans	$	46,505	$	—	$	—	$	46,505
	Other real estate owned	6,895			—		—	6,895
	Long-lived assets to be disposed of by sale	1,186			—		—	1,186
					Fair Value Measurements at Reporting Date Using
	As of December 31, 2013	Balance		Quoted Prices in		Significant Other		Significant
				Active Markets for		Observable		Unobservable
				Identical Assets		Inputs		Inputs
				(Level 1)		(Level 2)		(Level 3)
	Impaired loans	$	57,302	$	—	$	—	$	57,302
	Other real estate owned	8,502			—		—	8,502
	Long-lived assets to be disposed of by sale	1,186			—		—	1,186
	Impaired Loans. Collateralized impaired loans are reported at the fair value of the underlying collateral if repayment is expected solely from collateral. The impaired loans are reported at fair value through specific valuation allowance allocations. In addition, when it is determined that the fair value of an impaired loan is less than the recorded investment in the loan, the carrying value of the loan is adjusted to fair value through a charge to the allowance for loan losses. Collateral values are estimated using independent appraisals and management estimates of current market conditions. As of June 30, 2014, certain impaired loans with a carrying value of $63,149 were reduced by specific valuation allowance allocations of $6,952 and partial loan charge-offs of $9,692 resulting in a reported fair value of $46,505. As of December 31, 2013, certain impaired loans with a carrying value of $80,526 were reduced by specific valuation allowance allocations of $8,929 and partial loan charge-offs of $14,295 resulting in a reported fair value of $57,302.
	OREO.The fair values of OREO are estimated using independent appraisals and management estimates of current market conditions. Upon initial recognition, write-downs based on the foreclosed asset's fair value at foreclosure are reported through charges to the allowance for loan losses. Periodically, the fair value of foreclosed assets is remeasured with any subsequent write-downs charged to OREO expense in the period in which they are identified. Write-downs of $10 during the six months ended June 30, 2014 were based on management's estimate of the current fair value of the properties. Write-downs of $2,564 during the six months ended June 30, 2013, included $196 directly related to receipt of updated appraisals and $2,368 based on management estimates of the current fair value of properties.
	Long-lived Assets to be Disposed of by Sale. Long-lived assets to be disposed of by sale are carried at the lower of carrying value or fair value less estimated costs to sell. The fair values of long-lived assets to be disposed of by sale are based upon observable market data and management estimates of current market conditions. As of June 30, 2014 and December 31, 2013, the Company had long-lived assets to be disposed of by sale with a carrying value of $1,785 that was reduced by write-downs of $599 resulting in a fair value of $1,186.
	In addition, mortgage loans held for sale are required to be measured at the lower of cost or fair value. The fair value of mortgage loans held for sale is based upon binding contracts or quotes or bids from third party investors. As of June 30, 2014 and December 31, 2013, all mortgage loans held for sale were recorded at cost.
	The Company is required to disclose the fair value of financial instruments for which it is practical to estimate fair value. The methodologies for estimating the fair value of financial instruments that are measured at fair value on a recurring or non-recurring basis are discussed above. The methodologies for estimating the fair value of other financial instruments are discussed below. For financial instruments bearing a variable interest rate where no credit risk exists, it is presumed that recorded book values are reasonable estimates of fair value.
	Financial Assets. Carrying values of cash, cash equivalents and accrued interest receivable approximate fair values due to the liquid and/or short-term nature of these instruments. Fair values for investment securities held-to-maturity are obtained from an independent pricing service, which considers observable data that may include dealer quotes, market spreads, cash flows, the U.S. Treasury yield curve, live trading levels, trade execution data, market consensus prepayment speeds, credit information and the investment’s terms and conditions, among other things. Fair values of fixed rate loans and variable rate loans that reprice on an infrequent basis are estimated by discounting future cash flows using current interest rates at which similar loans with similar terms would be made to borrowers of similar credit quality. Carrying values of variable rate loans that reprice frequently, and with no change in credit risk, approximate the fair values of these instruments.
	Financial Liabilities. The fair values of demand deposits, savings accounts, securities sold under repurchase agreements and accrued interest payable are the amounts payable on demand at the reporting date. The fair values of fixed-maturity certificates of deposit are estimated using external market rates currently offered for deposits with similar remaining maturities. The carrying values of the interest bearing demand notes to the United States Treasury are deemed an approximation of fair values due to the frequent repayment and repricing at market rates. The fixed and floating rate subordinated debentures, floating rate subordinated term loan, notes payable to the FHLB, fixed rate subordinated term debt, and capital lease obligation are estimated by discounting future cash flows using current rates for advances with similar characteristics.
	Commitments to Extend Credit and Standby Letters of Credit. The fair value of commitments to extend credit and standby letters of credit, based on fees currently charged to enter into similar agreements, is not significant.
	The estimated fair values of financial instruments that are reported in the Company's consolidated balance sheets, segregated by the level of the valuation inputs within the fair value hierarchy utilized to measure fair value, are as follows:
							Fair Value Measurements at Reporting Date Using
	As of June 30, 2014	Carrying Amount		Estimated			Quoted Prices in			Significant Other		Significant
				Fair Value			Active Markets for			Observable		Unobservable
							Identical Assets			Inputs		Inputs
							(Level 1)			(Level 2)		(Level 3)
	Financial assets:
	Cash and cash equivalents	$	503,648	$	503,648		$	—		$	503,648	$	—
	Investment securities available-for-sale	1,506,996		1,506,996			—			1,506,996		—
	Investment securities held-to-maturity	586,989		592,682			—			592,682		—
	Accrued interest receivable	26,497		26,497			—			26,497		—
Mortgage servicing rights, net	13,443		25,812			—			25,812		—
Net loans	4,428,096		4,389,772			—			4,343,267		46,505
Total financial assets	$	7,065,669	$	7,045,407		$	—		$	6,998,902	$	46,505
Financial liabilities:
Total deposits, excluding time deposits	$	5,043,387	$	5,043,387		$	—		$	5,043,387	$	—
Time deposits	1,135,655		1,141,585			—			1,141,585		—
Securities sold under repurchase agreements	462,985		462,985			—			462,985		—
Other borrowed funds	20		20			—			20		—
Accrued interest payable	5,316		5,316			—			5,316		—
Long-term debt	36,893		35,381			—			35,381		—
Subordinated debentures held by subsidiary	82,477		75,200			—			75,200		—
trusts
Total financial liabilities	$	6,766,733	$	6,763,874		$	—		$	6,763,874	$	—
						Fair Value Measurements at Reporting Date Using
As of December 31, 2013	Carrying Amount		Estimated			Quoted Prices in			Significant Other		Significant
			Fair Value			Active Markets for			Observable		Unobservable
						Identical Assets			Inputs		Inputs
						(Level 1)			(Level 2)		(Level 3)
Financial assets:
Cash and cash equivalents	$	534,827	$	534,827		$	—		$	534,827	$	—
Investment securities available-for-sale	1,947,706		1,947,706			—			1,947,706		—
Investment securities held-to-maturity	203,837		205,926			—			205,926		—
Accrued interest receivable	26,450		26,450			—			26,450		—
Mortgage servicing rights, net	13,546		25,698			—			25,698		—
Net loans	4,259,514		4,246,539			—			4,189,237		57,302
Total financial assets	$	6,985,880	$	6,987,146		$	—		$	6,929,844	$	57,302
Financial liabilities:
Total deposits, excluding time deposits	$	4,943,033	$	4,943,033		$	—		$	4,943,033	$	—
Time deposits	1,190,717		1,196,250			—			1,196,250		—
Securities sold under repurchase agreements	457,437		457,437			—			457,437		—
Other borrowed funds	3		3			—			3		—
Accrued interest payable	4,963		4,963			—			4,963		—
Long-term debt	36,917		34,508			—			34,508		—
Subordinated debentures held by subsidiary	82,477		72,045			—			72,045		—
trusts
Total financial liabilities	$	6,715,547	$	6,708,239		$	—		$	6,708,239	$	—

Acquisitions

Acquisitions	6 Months Ended
	Jun. 30, 2014
Business Combinations [Abstract]	'
Acquisitions	'
	Acquisitions
	On February 10, 2014, the Company entered into an agreement and plan of merger to acquire all of the outstanding stock of Mountain West Financial Corp ("Mountain West"), a Montana-based bank holding company that operates one wholly-owned subsidiary bank, Mountain West Bank, NA, with branches located in five of the Company's current market areas in Montana. As of June 30, 2014, Mountain West had total assets of approximately $623,355, net loans of approximately $380,410 and deposits of approximately $519,820.
	Under the terms of the agreement and plan of merger, each outstanding share of Mountain West common stock will be canceled and converted into the right to receive 0.2552 shares of the Company's Class A common stock plus $7.125 in cash, or, if a Mountain West stockholder properly elects and subject to the limitations contained within the agreement and plan of merger, an amount in all cash or all stock intended to be substantially equal in value to the above described combination of stock and cash merger consideration. The value received by Mountain West stockholders in the aggregate and on a per share of Mountain West common stock basis will fluctuate prior to the completion of the merger based on the prevailing market price of the Company's Class A common stock at the time the transaction is consummated.
	The merger is expected to be completed after the close of business on July 31, 2014. Subject to regulatory approval, the Company anticipates Mountain West Bank, NA will be merged with and into FIB on October 18, 2014. For additional information regarding the acquisition, see Note 17 - Subsequent Events.

Related_Party_Transactions

Related Party Transactions	6 Months Ended
	Jun. 30, 2014
Related Party Transactions [Abstract]	'
Related Party Transactions Disclosure [Text Block]	'
	Related Party Transactions
	On May 2, 2014, the Company repurchased 20,000 shares of its Class A common stock from a director of the Company at a price of $24.77 per share. The repurchase was made in a privately negotiated transaction pursuant to a stock repurchase program approved by the Company's Board of Directors in November 2013. For additional information regarding the Company's stock repurchases, see Note 6 - Capital Stock.

Recent_Authoritative_Accountin

Recent Authoritative Accounting Guidance	6 Months Ended
	Jun. 30, 2014
New Accounting Pronouncements and Changes in Accounting Principles [Abstract]	'
Recent Authoritative Accounting Guidance	'
	Recent Authoritative Accounting Guidance
	ASU 2014-01 “Investments-Equity Method and Joint Ventures (Topic 323): Accounting for Investments in Qualified Affordable Housing Projects.” The amendments in ASU 2014-01 permit reporting entities to make an accounting policy election to account for their investments in qualified affordable housing projects using the proportional amortization method if certain conditions are met. The evaluation of whether conditions have been met to apply the proportional amortization method is conducted at the time of initial investment and subsequently reevaluated if there is a change in the nature of the investment or a change in the relationship with the limited liability entity that could result in the conditions no longer being met. The decision to apply the proportional amortization method of accounting should be applied consistently to all qualifying affordable housing project investments rather than on an individual investment basis. Under the proportional amortization method, an entity amortizes the initial cost of the investment in proportion to the tax credits and other tax benefits received and recognizes the net investment performance in the income statement as a component of income tax expense or benefit. The amendments in ASU 2014-01 are effective for the Company for annual reporting periods and interim reporting periods within those annual periods, beginning after December 15, 2014, with early adoption permitted.
	The Company adopted the amendments in ASU 2014-01 effective January 1, 2014. As of June 30, 2014, the Company had two investments in qualified affordable housing projects with an aggregate carrying value of $4,656 included in other assets on the Company's balance sheet. The Company elected to account for these investments using the proportional amortization method. During the three and six months ended June 30, 2014, income tax benefits associated with these projects of $7 and $14 were recognized as a component of income tax expense. The Company has commitments to invest additional amounts in these projects of $260 in 2014, $5,604 in 2015, $32 annually in 2016 through 2021, and $21 annually in 2022 and 2023.
	ASU 2014-04 “Receivables-Troubled Debt Restructurings by Creditors (Subtopic 310-40): Reclassification of Residential Real Estate Collateralized Consumer Mortgage Loans upon Foreclosure.” The amendments in ASU 2014-04 clarify that an in-substance repossession or foreclosures occurs, and a creditor is considered to have received physical possession of residential real estate property collateralizing a consumer mortgage loan, upon either (i) the creditor obtaining legal title to the residential real estate property upon completion of a foreclosure or (ii) the borrower conveying all interest in the residential real estate property to the creditor to satisfy the loan through completion of a deed in lieu of foreclosures or through a similar legal agreement. The amendments in ASU 2014-04 also require interim and annual disclosure of both (i) the amount of foreclosed residential real estate property held by the creditor and (ii) the recorded investment in consumer mortgage loans collateralized by residential real estate property that are in the process of foreclosure. The amendments in ASU 2014-04 are effective for the Company for annual periods, and interim periods within those annual periods, beginning after December 15, 2014 using either a modified retrospective transition method or a prospective transition method. The Company does not expect the amendments in ASU 2014-04 to have a material impact on the Company’s consolidated financial statements, results of operations or liquidity.
	ASU 2014-09 "Revenue from Contracts with Customers." The amendments in ASU 2014-09 introduce a new five-step revenue recognition model in which an entity should recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration to which the entity expects to be entitled in exchange for those goods or services. ASU 2014-09 also requires disclosures sufficient to enable users to understand the nature, amount, timing, and uncertainty of revenue and cash flows arising from contracts with customers, including qualitative and quantitative disclosures about contracts with customers, significant judgments and changes in judgments, and assets recognized from the costs to obtain or fulfill a contract. The amendments in ASU 2014-09 are effective for the Company for fiscal years beginning after December 15, 2016, including interim periods within that reporting period, and may be adopted retrospectively to each prior reporting period presented or retrospectively with the cumulative effect of initial adoption recognized at the date of initial application. The Company is currently evaluating the new guidance to determine the impact it will have on its consolidated financial statements, results of operations or liquidity.
	ASU 2014-11 "Repurchase-to-Maturity Transactions, Repurchase Financings, and Disclosures." The amendments in ASU 2014-11 expand secured borrowing treatment for certain repurchase agreements. Under the amendments in ASU 2014-11, repurchase-to-maturity transactions and repurchase agreements executed as repurchase financing transactions are required to be accounted for as secured borrowings. ASU 2014-11 requires additional disclosures about certain transactions accounted for as a sale in which the transferor retains substantially all of the exposure to the economic return on the transferred financial assets through an agreement with the same counterparty. ASU 2014-11 also requires disclosure of the types of collateral pledged and liabilities associated with an entity's repurchase agreements, securities lending transactions and repurchase-to-maturity transactions accounted for as secured borrowings. The accounting changes included in the amendments in ASU 2014-11 are effective for the Company on January 1, 2015. The disclosure requirements set forth in the amendment in ASU 2014-11 are effective for the Company for interim and annual periods beginning after December 31, 2014. The Company does not expect the amendments in ASU 2014-11 to have a material impact on the Company’s consolidated financial statements, results of operations or liquidity.

Subsequent_Events

Subsequent Events	6 Months Ended
	Jun. 30, 2014
Subsequent Events [Abstract]	'
Subsequent Events	'
	Subsequent Events
	Subsequent events have been evaluated for potential recognition and disclosure through the date financial statements were filed with the Securities and Exchange Commission. On July 24, 2014, the Company declared a quarterly dividend to common shareholders of $0.16 per share, to be paid on August 15, 2014 to shareholders of record as of August 5, 2014.
	On July 31, 2014, the Company completed the acquisition of Mountain West. Consideration for the acquisition consisted of cash of $38,479 and 1,378,230 shares of the Company's Class A common stock.
	No other events requiring recognition or disclosure were identified.

Investment_Securities_Tables

Investment Securities (Tables)	6 Months Ended
	Jun. 30, 2014
Investments, Debt and Equity Securities [Abstract]	'
Amortized Cost and Approximate Fair Values of Investment Securities	'
	The amortized cost and approximate fair values of investment securities are summarized as follows:
	June 30, 2014	Amortized		Gross			Gross			Estimated
		Cost		Unrealized			Unrealized			Fair
				Gains			Losses			Value
	Available-for-Sale:
	Obligations of U.S. government agencies	$	722,034	$	1,707		$	(5,174	)	$	718,567
	U.S. agency residential mortgage-backed securities & collateralized mortgage obligations	778,641		12,806			(3,383		)	788,064
	Private mortgage-backed securities	361		6			(2		)	365
	Total	$	1,501,036	$	14,519		$	(8,559	)	$	1,506,996
	June 30, 2014	Amortized		Gross			Gross			Estimated
		Cost		Unrealized			Unrealized			Fair
				Gains			Losses			Value
	Held-to-Maturity:
	State, county and municipal securities	$	179,131	$	6,159		$	(600	)	$	184,690
	Corporate securities	17,908		116			—			18,024
	U.S agency residential mortgage-backed securities &	389,950		18			—			389,968
	collateralized mortgage obligations
	Total	$	586,989	$	6,293		$	(600	)	$	592,682
	December 31, 2013	Amortized		Gross			Gross			Estimated
		Cost		Unrealized			Unrealized			Fair
				Gains			Losses			Value
	Available-for-Sale:
	Obligations of U.S. government agencies	$	774,055	$	1,432		$	(12,249	)	$	763,238
	U.S. agency residential mortgage-backed securities & collateralized mortgage obligations	1,197,295		11,905			(25,147		)	1,184,053
	Private mortgage-backed securities	407		9			(1		)	415
	Total	$	1,971,757	$	13,346		$	(37,397	)	$	1,947,706
	December 31, 2013	Amortized		Gross			Gross			Estimated
		Cost		Unrealized			Unrealized			Fair
				Gains			Losses			Value
	Held-to-Maturity:
	State, county and municipal securities	$	185,818	$	4,043		$	(2,049	)	$	187,812
	Corporate securities	18,019		103			(8		)	18,114
	Total	$	203,837	$	4,146		$	(2,057	)	$	205,926
Realized Gains (Losses) on Investments	'
	Gross realized gains and losses from the disposition of investment securities are summarized in the following table:
		Three Months Ended June 30,							Six Months Ended June 30,
		2014			2013				2014				2013
	Gross realized gains	$	18		$	4			$	243			$	12
	Gross realized losses	1			16				155				16
Gross Unrealized Losses and Fair Values of Investment Securities	'
	The following tables show the gross unrealized losses and fair values of investment securities, aggregated by investment category, and the length of time individual investment securities have been in a continuous unrealized loss position, as of June 30, 2014 and December 31, 2013.
		Less than 12 Months						12 Months or More							Total
	June 30, 2014	Fair		Gross				Fair			Gross				Fair		Gross
		Value		Unrealized				Value			Unrealized				Value		Unrealized
				Losses							Losses						Losses
	Available-for-Sale:
	Obligations of U.S. government agencies	$	61,265	$	(185	)		$	353,997		$	(4,989	)		$	415,262	$	(5,174	)
	U.S. agency residential mortgage-backed securities & collateralized mortgage obligations	47,884		(146		)		203,157			(3,237		)		251,041		(3,383		)
	Private mortgage-backed securities	—		—				95			(2		)		95		(2		)
	Total	$	109,149	$	(331	)		$	557,249		$	(8,228	)		$	666,398	$	(8,559	)
		Less than 12 Months						12 Months or More							Total
	June 30, 2014	Fair		Gross				Fair			Gross				Fair		Gross
		Value		Unrealized				Value			Unrealized				Value		Unrealized
				Losses							Losses						Losses
	Held-to-Maturity:
	State, county and municipal securities	$	267	$	(1	)		$	28,986		$	(599	)		$	29,253	$	(600	)
	Total	$	267	$	(1	)		$	28,986		$	(599	)		$	29,253	$	(600	)
		Less than 12 Months						12 Months or More							Total
	December 31, 2013	Fair		Gross				Fair			Gross				Fair		Gross
		Value		Unrealized				Value			Unrealized				Value		Unrealized
				Losses							Losses						Losses
	Available-for-Sale:
	Obligations of U.S. government agencies	$	458,385	$	(10,355	)		$	59,362		$	(1,894	)		$	517,747	$	(12,249	)
	U.S. agency residential mortgage-backed securities & collateralized mortgage obligations	634,199		(17,273		)		166,930			(7,874		)		801,129		(25,147		)
	Private mortgage-backed securities	—		—				104			(1		)		104		(1		)
	Total	$	1,092,584	$	(27,628	)		$	226,396		$	(9,769	)		$	1,318,980	$	(37,397	)
		Less than 12 Months						12 Months or More							Total
	December 31, 2013	Fair		Gross				Fair			Gross				Fair		Gross
		Value		Unrealized				Value			Unrealized				Value		Unrealized
				Losses							Losses						Losses
	Held-to-Maturity:
	State, county and municipal securities	$	37,550	$	(1,319	)		$	14,296		$	(730	)		$	51,846	$	(2,049	)
	Corporate securities	7,294		(8		)		—			—				7,294		(8		)
	Total	$	44,844	$	(1,327	)		$	14,296		$	(730	)		$	59,140	$	(2,057	)
Maturities of Investment Securities	'
	Maturities of investment securities at June 30, 2014 are shown below. Maturities of mortgage-backed securities have been adjusted to reflect shorter maturities based upon estimated prepayments of principal. All other investment securities maturities are shown at contractual maturity dates.
		Available-for-Sale						Held-to-Maturity
	June 30, 2014	Amortized		Estimated				Amortized			Estimated
		Cost		Fair Value				Cost			Fair Value
	Within one year	$	235,880	$	238,377			$	75,137		$	75,805
	After one year but within five years	1,046,202		1,050,653				262,721			265,277
	After five years but within ten years	203,374		202,197				174,980			176,267
	After ten years	15,580		15,769				74,151			75,333
	Total	$	1,501,036	$	1,506,996			$	586,989		$	592,682

Loans_Tables

Loans (Tables)	6 Months Ended
	Jun. 30, 2014
Receivables [Abstract]	'
Schedule of Loans by Class	'
	The following table presents loans by class as of the dates indicated:
		June 30,				December 31,
		2014				2013
	Real estate loans:
	Commercial	$	1,464,947			$	1,449,174
	Construction:
	Land acquisition & development	192,289				205,911
	Residential	82,121				76,488
	Commercial	86,599				69,236
	Total construction loans	361,009				351,635
	Residential	894,502				867,912
	Agricultural	162,428				173,534
	Total real estate loans	2,882,886				2,842,255
	Consumer:
	Indirect consumer	512,063				476,012
	Other consumer	133,604				133,039
	Credit card	61,368				62,536
	Total consumer loans	707,035				671,587
	Commercial	727,482				676,544
	Agricultural	130,280				111,872
	Other, including overdrafts	2,016				1,734
	Loans held for investment	4,449,699				4,303,992
	Mortgage loans held for sale	56,663				40,861
	Total loans	$	4,506,362			$	4,344,853
Schedule of Recorded Investment in Past Due Loans by Class	'
	The following tables present the contractual aging of the Company’s recorded investment in past due loans by class as of the dates indicated:
											Total Loans
		30 - 59			60 - 89			> 90			30 or More
		Days			Days			Days			Days		Current		Non-accrual		Total
	As of June 30, 2014	Past Due			Past Due			Past Due			Past Due		Loans		Loans		Loans
	Real estate
	Commercial	$	5,343		$	2,540		$	40		$	7,923	$	1,418,602	$	38,422	$	1,464,947
	Construction:
	Land acquisition & development	782			123			—			905		180,094		11,290		192,289
	Residential	90			1,226			—			1,316		80,152		653		82,121
	Commercial	—			—			—			—		84,019		2,580		86,599
	Total construction loans	872			1,349			—			2,221		344,265		14,523		361,009
	Residential	3,493			823			665			4,981		884,261		5,260		894,502
	Agricultural	29			72			—			101		155,228		7,099		162,428
	Total real estate loans	9,737			4,784			705			15,226		2,802,356		65,304		2,882,886
	Consumer:
	Indirect consumer	2,467			404			15			2,886		508,777		400		512,063
	Other consumer	780			210			16			1,006		131,864		734		133,604
	Credit card	281			239			335			855		60,496		17		61,368
	Total consumer loans	3,528			853			366			4,747		701,137		1,151		707,035
	Commercial	3,223			718			325			4,266		710,886		12,330		727,482
	Agricultural	1,390			17			125			1,532		128,367		381		130,280
	Other, including overdrafts	—			—			1			1		2,015		—		2,016
	Loans held for investment	17,878			6,372			1,522			25,772		4,344,761		79,166		4,449,699
	Mortgage loans originated for sale	—			—			—			—		56,663		—		56,663
	Total loans	$	17,878		$	6,372		$	1,522		$	25,772	$	4,401,424	$	79,166	$	4,506,362
											Total Loans
		30 - 59			60 - 89			> 90			30 or More
		Days			Days			Days			Days		Current		Non-accrual		Total
	As of December 31, 2013	Past Due			Past Due			Past Due			Past Due		Loans		Loans		Loans
	Real estate
	Commercial	$	5,924		$	2,472		$	22		$	8,418	$	1,391,823	$	48,933	$	1,449,174
	Construction:
	Land acquisition & development	1,062			468			38			1,568		188,074		16,269		205,911
	Residential	933			250			—			1,183		73,933		1,372		76,488
	Commercial	584			—			—			584		68,427		225		69,236
	Total construction loans	2,579			718			38			3,335		330,434		17,866		351,635
	Residential	3,630			206			1,162			4,998		856,800		6,114		867,912
	Agricultural	328			646			—			974		163,986		8,574		173,534
	Total real estate loans	12,461			4,042			1,222			17,725		2,743,043		81,487		2,842,255
	Consumer:
	Indirect consumer	3,303			430			9			3,742		471,906		364		476,012
	Other consumer	925			130			1			1,056		131,508		475		133,039
	Credit card	364			187			515			1,066		61,451		19		62,536
	Total consumer loans	4,592			747			525			5,864		664,865		858		671,587
	Commercial	2,791			1,186			563			4,540		660,035		11,969		676,544
	Agricultural	453			672			—			1,125		110,622		125		111,872
	Other, including overdrafts	—			—			—			—		1,734		—		1,734
	Loans held for investment	20,297			6,647			2,310			29,254		4,180,299		94,439		4,303,992
	Mortgage loans originated for sale	—			—			—			—		40,861		—		40,861
	Total loans	$	20,297		$	6,647		$	2,310		$	29,254	$	4,221,160	$	94,439	$	4,344,853
Schedule of Recorded Investment in Impaired Loans	'
	The following tables present information on the Company’s recorded investment in impaired loans as of dates indicated:
	As of June 30, 2014	Unpaid			Recorded			Recorded			Total		Related
		Total			Investment			Investment			Recorded		Allowance
		Principal			With No			With			Investment
		Balance			Allowance			Allowance
	Real estate:
	Commercial	$	52,690		$	24,961		$	25,622		$	50,583	$	3,566
	Construction:
	Land acquisition & development	15,601			8,098			3,869			11,967		647
	Residential	1,096			653			—			653		—
	Commercial	2,749			269			2,446			2,715		908
	Total construction loans	19,446			9,020			6,315			15,335		1,555
	Residential	7,222			4,885			375			5,260		301
	Agricultural	9,191			6,656			2,439			9,095		133
	Total real estate loans	88,549			45,522			34,751			80,273		5,555
	Commercial	14,752			10,709			2,679			13,388		1,176
	Agricultural	792			419			322			741		221
	Total	$	104,093		$	56,650		$	37,752		$	94,402	$	6,952
	As of December 31, 2013	Unpaid			Recorded			Recorded			Total		Related
		Total			Investment			Investment			Recorded		Allowance
		Principal			With No			With			Investment
		Balance			Allowance			Allowance
	Real estate:
	Commercial	$	64,780		$	29,216		$	33,937		$	63,153	$	5,210
	Construction:
	Land acquisition & development	23,906			9,901			7,226			17,127		1,434
	Residential	1,816			1,095			277			1,372		26
	Commercial	397			279			84			363		85
	Total construction loans	26,119			11,275			7,587			18,862		1,545
	Residential	9,448			5,081			967			6,048		249
	Agricultural	8,895			6,429			2,370			8,799		335
	Total real estate loans	109,242			52,001			44,861			96,862		7,339
	Commercial	15,448			10,684			2,901			13,585		1,504
	Agricultural	177			39			86			125		86
	Total	$	124,867		$	62,724		$	47,848		$	110,572	$	8,929
	The following tables present the average recorded investment in and income recognized on impaired loans for the periods indicated:
		Three Months Ended June 30,
		2014								2013
		Average Recorded Investment				Income Recognized				Average Recorded Investment			Income Recognized
	Real estate:
	Commercial	$	57,588			$	241			$	67,605		$	272
	Construction:
	Land acquisition & development	13,563				11				19,007			15
	Residential	785				—				1,569			—
	Commercial	1,471				2				6,346			—
	Total construction loans	15,819				13				26,922			15
	Residential	5,852				1				8,311			5
	Agricultural	9,747				25				8,255			4
	Total real estate loans	89,006				280				111,093			296
	Commercial	14,162				14				16,087			18
	Agricultural	742				6				373			4
	Total	$	103,910			$	300			$	127,553		$	318
		Six Months Ended June 30,
		2014								2013
		Average Recorded Investment				Income Recognized				Average Recorded Investment			Income Recognized
	Real estate:
	Commercial	$	60,870			$	457			$	67,192		$	610
	Construction:
	Land acquisition & development	14,554				22				20,123			456
	Residential	1,051				—				2,040			—
	Commercial	918				4				7,118			—
	Total construction loans	16,523				26				29,281			456
	Residential	5,969				3				9,429			9
Agricultural	9,830				29				6,611			8
Total real estate loans	93,192				515				112,513			1,083
Commercial	14,231				28				14,484			36
Agricultural	538				12				502			8
Total	$	107,961			$	555			$	127,499		$	1,127
Schedule of Loans Renegotiated in Troubled Debt Restructurings	'
	The following tables present information on the Company's troubled debt restructurings that occurred during the three months ended June 30, 2014:
			Number of Notes		Type of Concession										Principal Balance at Restructure Date
	Three Months Ended June 30, 2014				Interest only period			Extension of terms or maturity			Interest rate adjustment		Other (1)
	Commercial real estate		4		$	458		$	226		$	—	$	679	$	1,363
	Commercial		2		72			—			—		—		72
	Total loans restructured during period		6		$	530		$	226		$	—	$	679	$	1,435
	(1) Other includes concessions that reduce or defer payments for a specified period of time and/or do not fit into other
	designated categories.
			Number of Notes		Type of Concession										Principal Balance at Restructure Date
	Six Months Ended June 30, 2014				Interest only period			Extension of terms or maturity			Interest rate adjustment		Other (1)
	Commercial real estate		8		$	—		$	226		$	—	$	921	$	1,147
	Commercial		4		299			2,931			—		30		3,260
	Total loans restructured during period		12		$	299		$	3,157		$	—	$	951	$	4,407
	(1) Other includes concessions that reduce or defer payments for a specified period of time and/or do not fit into other
	designated categories.
	The Company considers a payment default to occur on troubled debt restructurings when the loan is 90 days or more past due or was placed on non-accrual status after the modification.
		Three Months Ended June 30, 2014				Six Months Ended June 30, 2014
		Number of Notes		Balance		Number of Notes		Balance
	Commercial	2		72		2		72
	Total	2		72		2		72
Schedule of Recorded Investment in Criticized Loans by Class and Credit Quality Indicator	'
	The following tables present the Company’s recorded investment in criticized loans by class and credit quality indicator based on the most recent analysis performed as of the dates indicated:
	As of June 30, 2014	Other Assets			Substandard			Doubtful			Total
		Especially									Criticized
		Mentioned									Loans
	Real estate:
	Commercial	$	81,539		$	82,558		$	15,371		$	179,468
	Construction:
	Land acquisition & development	12,580			13,053			2,626			28,259
	Residential	2,190			1,788			—			3,978
	Commercial	186			269			2,446			2,901
	Total construction loans	14,956			15,110			5,072			35,138
	Residential	11,028			9,017			588			20,633
	Agricultural	9,638			15,755			2,439			27,832
	Total real estate loans	117,161			122,440			23,470			263,071
	Consumer:
	Indirect consumer	769			1,575			133			2,477
	Other consumer	529			927			398			1,854
	Credit card	—			390			1,219			1,609
	Total consumer loans	1,298			2,892			1,750			5,940
	Commercial	30,522			26,203			3,573			60,298
	Agricultural	11,290			4,209			322			15,821
	Total	$	160,271		$	155,744		$	29,115		$	345,130
	As of December 31, 2013	Other Assets			Substandard			Doubtful			Total
		Especially									Criticized
		Mentioned									Loans
	Real estate:
	Commercial	$	79,747		$	86,426		$	24,840		$	191,013
	Construction:
	Land acquisition & development	13,211			19,677			7,329			40,217
	Residential	1,859			1,649			277			3,785
	Commercial	—			409			84			493
	Total construction loans	15,070			21,735			7,690			44,495
	Residential	7,500			7,188			4,184			18,872
	Agricultural	13,597			10,245			2,370			26,212
	Total real estate loans	115,914			125,594			39,084			280,592
	Consumer:
	Indirect consumer	875			1,524			115			2,514
	Other consumer	573			969			268			1,810
	Credit card	—			392			2,010			2,402
	Total consumer loans	1,448			2,885			2,393			6,726
	Commercial	33,318			23,833			3,745			60,896
	Agricultural	8,401			1,788			86			10,275
	Total	$	159,081		$	154,100		$	45,308		$	358,489

Allowance_for_Loan_Losses_Tabl

Allowance for Loan Losses (Tables)	6 Months Ended
	Jun. 30, 2014
Receivables [Abstract]	'
Schedule of Allowance for Loan Losses by Portfolio Segment	'
	The following tables present a summary of changes in the allowance for loan losses by portfolio segment for the periods indicated.
	Three Months Ended June 30, 2014	Real Estate			Consumer			Commercial			Agriculture			Other		Total
	Allowance for loan losses:
	Beginning balance	$	59,830		$	5,377		$	15,701		$	463		$	—	$	81,371
	Provision charged to operating expense	(2,011		)	346			(494		)	158			—		(2,001		)
	Less loans charged-off	(1,158		)	(934		)	(534		)	—			—		(2,626		)
	Add back recoveries of loans previously	651			558			313			—			—		1,522
	charged-off
	Ending balance	$	57,312		$	5,347		$	14,986		$	621		$	—	$	78,266
	Six Months Ended June 30, 2014	Real Estate			Consumer			Commercial			Agriculture			Other		Total
	Allowance for loan losses:
	Beginning balance	$	63,923		$	6,193		$	14,747		$	476		$	—	$	85,339
	Provision charged to operating expense	(5,386		)	(232		)	(1,566		)	183			—		(7,001		)
	Less loans charged-off	(2,243		)	(1,780		)	(1,330		)	(64		)	—		(5,417		)
	Add back recoveries of loans previously	1,018			1,166			3,135			26			—		5,345
	charged-off
	Ending balance	$	57,312		$	5,347		$	14,986		$	621		$	—	$	78,266
	As of June 30, 2014	Real Estate			Consumer			Commercial			Agriculture			Other		Total
	Allowance for loan losses:
	Loans individually evaluated for impairment	$	5,555		$	—		$	1,176		$	221		$	—	$	6,952
	Loans collectively evaluated for impairment	51,757			5,347			13,810			400			—		71,314
	Allowance for loan losses	$	57,312		$	5,347		$	14,986		$	621		$	—	$	78,266
	As of June 30, 2014	Real Estate			Consumer			Commercial			Agriculture			Other		Total
	Total loans:
	Individually evaluated for impairment	$	80,273		$	—		$	13,388		$	741		$	—	$	94,402
	Collectively evaluated for impairment	2,859,276			707,035			714,094			129,539			2,016		4,411,960
	Total loans	$	2,939,549		$	707,035		$	727,482		$	130,280		$	2,016	$	4,506,362
	Three Months Ended June 30, 2013	Real Estate			Consumer			Commercial			Agriculture			Other		Total
	Allowance for loan losses:
	Beginning balance	$	71,666		$	7,088		$	18,670		$	480		$	—	$	97,904
	Provision charged to operating expense	(1,009		)	579			778			27			—		375
	Less loans charged-off	(2,027		)	(1,299		)	(569		)	—			—		(3,895		)
	Add back recoveries of loans previously	2,873			672			596			3			—		4,144
	charged-off
	Ending balance	$	71,503		$	7,040		$	19,475		$	510		$	—	$	98,528
	Six Months Ended June 30, 2013	Real Estate			Consumer			Commercial			Agriculture			Other		Total
	Allowance for loan losses:
	Beginning balance	$	75,782		$	7,140		$	17,085		$	504		$	—	$	100,511
	Provision charged to operating expense	(2,044		)	1,116			1,799			4			—		875
	Less loans charged-off	(6,170		)	(2,361		)	(1,380		)	(4		)	—		(9,915		)
	Add back recoveries of loans previously	3,935			1,145			1,971			6			—		7,057
	charged-off
	Ending balance	$	71,503		$	7,040		$	19,475		$	510		$	—	$	98,528
	As of June 30, 2013	Real Estate			Consumer			Commercial			Agriculture			Other		Total
	Allowance for loan losses:
	Loans individually evaluated for impairment	$	10,267		$	—		$	5,205		$	22		$	—	$	15,494
	Loans collectively evaluated for impairment	61,236			7,040			14,270			488			—		83,034
	Allowance for loan losses	$	71,503		$	7,040		$	19,475		$	510		$	—	$	98,528
	As of June 30, 2013	Real Estate			Consumer			Commercial			Agriculture			Other		Total
	Total loans:
	Individually evaluated for impairment	$	107,241		$	—		$	16,710		$	139		$	—	$	124,090
	Collectively evaluated for impairment	2,732,400			652,944			666,539			121,391			—		4,173,274
	Total loans	$	2,839,641		$	652,944		$	683,249		$	121,530		$	—	$	4,297,364

OREO_Tables

OREO (Tables)	6 Months Ended
	Jun. 30, 2014
Repossessed Assets [Abstract]	'
Other Real Estate Owned Roll Forward	'
	Information with respect to the Company's other real estate owned follows:
		Three Months Ended June 30,						Six Months Ended June 30,
		2014			2013			2014			2013
	Beginning balance	$	16,594		$	32,470		$	15,504		$	32,571
	Additions	984			3,224			4,399			8,555
	Capitalized improvements	—			3			—			13
	Valuation adjustments	(10		)	(259		)	(10		)	(2,564		)
	Dispositions	(1,143		)	(12,656		)	(3,468		)	(15,793		)
	Ending balance	$	16,425		$	22,782		$	16,425		$	22,782

Earnings_per_Share_Tables

Earnings per Share (Tables)	6 Months Ended
	Jun. 30, 2014
Earnings Per Share [Abstract]	'
Computation of Basic and Diluted Earnings per Share	'
	The following table sets forth the computation of basic and diluted earnings per share for the three and six month periods ended June 30, 2014 and 2013.
		Three Months Ended June 30,				Six Months Ended June 30,
		2014		2013		2014		2013
	Net income	$	21,077	$	21,505	$	42,470	$	41,549
	Weighted average common shares outstanding for basic earnings per share computation	44,044,260		43,480,502		44,021,166		43,335,682
	Dilutive effects of stock-based compensation	531,703		427,785		572,689		376,978
	Weighted average common shares outstanding for diluted earnings per common share computation	44,575,963		43,908,287		44,593,855		43,712,660
	Basic earnings per common share	$	0.48	$	0.49	$	0.96	$	0.96
	Diluted earnings per common share	$	0.47	$	0.49	$	0.95	$	0.95

Regulatory_Capital_Tables

Regulatory Capital (Tables)	6 Months Ended
	Jun. 30, 2014
Banking and Thrift [Abstract]	'
Schedule of Compliance with Regulatory Capital Requirements under Banking Regulations	'
	Actual capital amounts and ratios and selected minimum regulatory thresholds for the Company and its bank subsidiary, First Interstate Bank (“FIB”), as of June 30, 2014 and December 31, 2013 are presented in the following tables:
		Actual				Adequately Capitalized				Well Capitalized
		Amount		Ratio		Amount		Ratio		Amount		Ratio
	June 30, 2014
	Total risk-based capital:
	Consolidated	$	850,614	16.7	%	$	407,804	8	%	NA		NA
	FIB	740,815		14.6		406,334		8		$	507,917	10	%
	Tier 1 risk-based capital:
	Consolidated	765,715		15		203,902		4		NA		NA
	FIB	668,143		13.2		203,167		4		$	304,750	6
	Leverage capital ratio:
	Consolidated	765,715		10.4		295,843		4		NA		NA
	FIB	668,143		9.1		295,201		4		$	369,002	5
		Actual				Adequately Capitalized				Well Capitalized
		Amount		Ratio		Amount		Ratio		Amount		Ratio
	December 31, 2013
	Total risk-based capital:
	Consolidated	$	829,443	16.8	%	$	396,210	8	%	NA		NA
	FIB	723,955		14.7		394,038		8		$	492,548	10	%
	Tier 1 risk-based capital:
	Consolidated	739,246		14.9		198,105		4		NA		NA
	FIB	650,093		13.2		197,019		4		$	295,529	6
	Leverage capital ratio:
	Consolidated	739,246		10.1		293,414		4		NA		NA
	FIB	650,093		8.9		292,199		4		$	365,248	5

Other_Comprehensive_Income_Tab

Other Comprehensive Income (Tables)	6 Months Ended
	Jun. 30, 2014
Equity [Abstract]	'
Schedule of Comprehensive Income (Loss)	'
	Other Comprehensive Income/Loss
	The gross amounts of each component of other comprehensive income (loss) and the related tax effects are as follows:
		Pre-tax						Tax Expense (Benefit)						Net of Tax
	Three Months Ended June 30,	2014			2013			2014			2013			2014			2013
	Investment securities available-for sale:
	Change in net unrealized gains/losses	$	2,816		$	(35,625	)	$	1,108		$	(14,018	)	$	1,708		$	(21,607	)
	during period
	Reclassification adjustment for net (gains)	(17		)	12			(7		)	5			(10		)	7
	losses included in net income
	Defined benefits post-retirement benefit plan:
	Change in net actuarial loss	35			35			14			14			21			21
	Total other comprehensive income (loss)	$	2,834		$	(35,578	)	$	1,115		$	(13,999	)	$	1,719		$	(21,579	)
		Pre-tax						Tax Expense (Benefit)						Net of Tax
	Six Months Ended June 30,	2014			2013			2014			2013			2014			2013
	Investment securities available-for sale:
	Change in net unrealized gains/losses	$	17,167		$	(41,342	)	$	6,755		$	(16,268	)	$	10,412		$	(25,074	)
	during period
	Reclassification adjustment for net (gains)	(88		)	4			(35		)	2			(53		)	2
	losses included in net income
	Defined benefits post-retirement benefit plan:
	Change in net actuarial loss	70			70			28			28			42			42
	Total other comprehensive (loss) income	$	17,149		$	(41,268	)	$	6,748		$	(16,238	)	$	10,401		$	(25,030	)
Schedule of Accumulated Other Comprehensive Income (Loss)	'
	The components of accumulated other comprehensive loss, net of income tax benefits, are as follows:
		June 30,			December 31,
		2014			2013
	Net unrealized gain on investment securities available-for-sale	$	(4,219	)	$	(14,578	)
	Net actuarial loss on defined benefit post-retirement benefit plans	(1,421		)	(1,463		)
	Net accumulated other comprehensive loss	$	(5,640	)	$	(16,041	)

Fair_Value_Measurements_Tables

Fair Value Measurements (Tables)	6 Months Ended
	Jun. 30, 2014
Fair Value Disclosures [Abstract]	'
Schedule of Financial Assets and Financial Liabilities Measured at Fair Value on a Recurring Basis	'
	Financial assets and financial liabilities measured at fair value on a recurring basis are as follows:
				Fair Value Measurements at Reporting Date Using
	As of June 30, 2014	Balance		Quoted Prices in		Significant Other			Significant
				Active Markets for		Observable			Unobservable
				Identical Assets		Inputs			Inputs
				(Level 1)		(Level 2)			(Level 3)
	Investment securities available-for-sale:
	Obligations of U.S. government agencies	$	718,567	$	—	$	718,567		$	—
	U.S. agencies mortgage-backed securities & collateralized mortgage obligations	788,064			—	788,064				—
	Private mortgage-backed securities	365			—	365				—
	Mortgage servicing rights	25,812			—	25,812				—
				Fair Value Measurements at Reporting Date Using
	As of December 31, 2013	Balance		Quoted Prices in		Significant Other			Significant
				Active Markets for		Observable			Unobservable
				Identical Assets		Inputs			Inputs
				(Level 1)		(Level 2)			(Level 3)
	Investment securities available-for-sale:
	Obligations of U.S. government agencies	$	763,238	$	—	$	763,238		$	—
	U.S. agencies mortgage-backed securities & collateralized mortgage obligations	1,184,053			—	1,184,053				—
	Private mortgage-backed securities	415			—	415				—
	Mortgage servicing rights	25,698			—	25,698				—
Schedule of Financial Assets and Financial Liabilities Measured at Fair Value on a Non-Recurring Basis	'
	The following table presents information about the Company’s assets and liabilities measured at fair value on a non-recurring basis.
					Fair Value Measurements at Reporting Date Using
	As of June 30, 2014	Balance		Quoted Prices in		Significant Other		Significant
				Active Markets for		Observable		Unobservable
				Identical Assets		Inputs		Inputs
				(Level 1)		(Level 2)		(Level 3)
	Impaired loans	$	46,505	$	—	$	—	$	46,505
	Other real estate owned	6,895			—		—	6,895
	Long-lived assets to be disposed of by sale	1,186			—		—	1,186
					Fair Value Measurements at Reporting Date Using
	As of December 31, 2013	Balance		Quoted Prices in		Significant Other		Significant
				Active Markets for		Observable		Unobservable
				Identical Assets		Inputs		Inputs
				(Level 1)		(Level 2)		(Level 3)
	Impaired loans	$	57,302	$	—	$	—	$	57,302
	Other real estate owned	8,502			—		—	8,502
	Long-lived assets to be disposed of by sale	1,186			—		—	1,186
Schedule of Estimated Fair Values of Financial Instruments by Level of Valuation Inputs	'
	The estimated fair values of financial instruments that are reported in the Company's consolidated balance sheets, segregated by the level of the valuation inputs within the fair value hierarchy utilized to measure fair value, are as follows:
							Fair Value Measurements at Reporting Date Using
	As of June 30, 2014	Carrying Amount		Estimated			Quoted Prices in			Significant Other		Significant
				Fair Value			Active Markets for			Observable		Unobservable
							Identical Assets			Inputs		Inputs
							(Level 1)			(Level 2)		(Level 3)
	Financial assets:
	Cash and cash equivalents	$	503,648	$	503,648		$	—		$	503,648	$	—
	Investment securities available-for-sale	1,506,996		1,506,996			—			1,506,996		—
	Investment securities held-to-maturity	586,989		592,682			—			592,682		—
	Accrued interest receivable	26,497		26,497			—			26,497		—
	Mortgage servicing rights, net	13,443		25,812			—			25,812		—
	Net loans	4,428,096		4,389,772			—			4,343,267		46,505
	Total financial assets	$	7,065,669	$	7,045,407		$	—		$	6,998,902	$	46,505
	Financial liabilities:
	Total deposits, excluding time deposits	$	5,043,387	$	5,043,387		$	—		$	5,043,387	$	—
	Time deposits	1,135,655		1,141,585			—			1,141,585		—
	Securities sold under repurchase agreements	462,985		462,985			—			462,985		—
	Other borrowed funds	20		20			—			20		—
	Accrued interest payable	5,316		5,316			—			5,316		—
	Long-term debt	36,893		35,381			—			35,381		—
	Subordinated debentures held by subsidiary	82,477		75,200			—			75,200		—
	trusts
	Total financial liabilities	$	6,766,733	$	6,763,874		$	—		$	6,763,874	$	—
							Fair Value Measurements at Reporting Date Using
	As of December 31, 2013	Carrying Amount		Estimated			Quoted Prices in			Significant Other		Significant
				Fair Value			Active Markets for			Observable		Unobservable
							Identical Assets			Inputs		Inputs
							(Level 1)			(Level 2)		(Level 3)
	Financial assets:
	Cash and cash equivalents	$	534,827	$	534,827		$	—		$	534,827	$	—
	Investment securities available-for-sale	1,947,706		1,947,706			—			1,947,706		—
	Investment securities held-to-maturity	203,837		205,926			—			205,926		—
	Accrued interest receivable	26,450		26,450			—			26,450		—
	Mortgage servicing rights, net	13,546		25,698			—			25,698		—
	Net loans	4,259,514		4,246,539			—			4,189,237		57,302
	Total financial assets	$	6,985,880	$	6,987,146		$	—		$	6,929,844	$	57,302
	Financial liabilities:
	Total deposits, excluding time deposits	$	4,943,033	$	4,943,033		$	—		$	4,943,033	$	—
	Time deposits	1,190,717		1,196,250			—			1,196,250		—
	Securities sold under repurchase agreements	457,437		457,437			—			457,437		—
	Other borrowed funds	3		3			—			3		—
	Accrued interest payable	4,963		4,963			—			4,963		—
	Long-term debt	36,917		34,508			—			34,508		—
	Subordinated debentures held by subsidiary	82,477		72,045			—			72,045		—
	trusts
	Total financial liabilities	$	6,715,547	$	6,708,239		$	—		$	6,708,239	$	—

Amortized_Cost_and_Approximate

Amortized Cost and Approximate Fair Values of Investment Securities (Details) (USD $)	3 Months Ended		6 Months Ended
In Thousands, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013	Dec. 31, 2013
Schedule of Available for Sale and Held-to-Maturity Securities [Line Items]	'	'	'	'	'
Available-for-Sale Securities, Gross Realized Gains	$18	$4	$243	$12	'
Available-for-sale Securities, Gross Realized Losses	1	16	155	16	'
Available-for-Sale:	'	'	'	'	'
Available-for-Sale, Amortized Cost	1,501,036	'	1,501,036	'	1,971,757
Available-for-sale Securities, Gross Unrealized Gain1	14,519	'	14,519	'	13,346
Available-for-sale Securities, Gross Unrealized Loss1	-8,559	'	-8,559	'	-37,397
Available-for-Sale, Estimated Fair Value	1,506,996	'	1,506,996	'	1,947,706
Held-to-Maturity:	'	'	'	'	'
Held-to-Maturity, Amortized Cost	586,989	'	586,989	'	203,837
Held-to-maturity Securities, Gross Unrealized Gain1	6,293	'	6,293	'	4,146
Held-to-maturity Securities, Gross Unrealized Loss1	-600	'	-600	'	-2,057
Held-to-Maturity, Estimated Fair Value	592,682	'	592,682	'	205,926
Obligations of U.S. government agencies	'	'	'	'	'
Available-for-Sale:	'	'	'	'	'
Available-for-Sale, Amortized Cost	722,034	'	722,034	'	774,055
Available-for-sale Securities, Gross Unrealized Gain1	1,707	'	1,707	'	1,432
Available-for-sale Securities, Gross Unrealized Loss1	-5,174	'	-5,174	'	-12,249
Available-for-Sale, Estimated Fair Value	718,567	'	718,567	'	763,238
U.S. agency residential mortgage-backed securities & collateralized mortgage obligations	'	'	'	'	'
Available-for-Sale:	'	'	'	'	'
Available-for-Sale, Amortized Cost	778,641	'	778,641	'	1,197,295
Available-for-sale Securities, Gross Unrealized Gain1	12,806	'	12,806	'	11,905
Available-for-sale Securities, Gross Unrealized Loss1	-3,383	'	-3,383	'	-25,147
Available-for-Sale, Estimated Fair Value	788,064	'	788,064	'	1,184,053
Held-to-Maturity:	'	'	'	'	'
Held-to-Maturity, Amortized Cost	389,950	'	389,950	'	'
Held-to-maturity Securities, Gross Unrealized Gain1	18	'	18	'	'
Held-to-maturity Securities, Gross Unrealized Loss1	0	'	0	'	'
Held-to-Maturity, Estimated Fair Value	389,968	'	389,968	'	'
Private mortgage-backed securities	'	'	'	'	'
Available-for-Sale:	'	'	'	'	'
Available-for-Sale, Amortized Cost	361	'	361	'	407
Available-for-sale Securities, Gross Unrealized Gain1	6	'	6	'	9
Available-for-sale Securities, Gross Unrealized Loss1	-2	'	-2	'	-1
Available-for-Sale, Estimated Fair Value	365	'	365	'	415
State, county and municipal securities	'	'	'	'	'
Held-to-Maturity:	'	'	'	'	'
Held-to-Maturity, Amortized Cost	179,131	'	179,131	'	185,818
Held-to-maturity Securities, Gross Unrealized Gain1	6,159	'	6,159	'	4,043
Held-to-maturity Securities, Gross Unrealized Loss1	-600	'	-600	'	-2,049
Held-to-Maturity, Estimated Fair Value	184,690	'	184,690	'	187,812
Corporate securities	'	'	'	'	'
Held-to-Maturity:	'	'	'	'	'
Held-to-Maturity, Amortized Cost	17,908	'	17,908	'	18,019
Held-to-maturity Securities, Gross Unrealized Gain1	116	'	116	'	103
Held-to-maturity Securities, Gross Unrealized Loss1	0	'	0	'	-8
Held-to-Maturity, Estimated Fair Value	$18,024	'	$18,024	'	$18,114

Investment_Securities_Realized

Investment Securities Realized Gains (Losses) on Investments (Details) (USD $)	3 Months Ended		6 Months Ended
In Thousands, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Investments, Debt and Equity Securities [Abstract]	'	'	'	'
Gross realized gains	$18	$4	$243	$12
Gross realized losses	$1	$16	$155	$16

Investment_Securities_Gross_Un

Investment Securities Gross Unrealized Losses and Fair Values of Investment Securities (Details) (USD $)	Jun. 30, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified	securities	securities
Available-for-Sale:	'	'
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	$109,149	$1,092,584
Available-for-sale Securities, Continuous Unrealized Loss Position, Less Than 12 months, Aggregate Loss1	-331	-27,628
Available-for-Sale, 12 Months or More Fair Value	557,249	226,396
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 months or Longer, Aggregate Loss1	-8,228	-9,769
Available-for-Sale, Total Fair Value	666,398	1,318,980
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Loss1	-8,559	-37,397
Held-to-Maturity:	'	'
Held-to-Maturity, Less than 12 Months Fair Value	267	44,844
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less Than 12 months, Aggregate Loss1	-1	-1,327
Held-to-Maturity, 12 Months or More Fair Value	28,986	14,296
Held-to-Maturity, 12 Months or More Gross Unrealized Losses	-599	-730
Held-to-Maturity, Total Fair Value	29,253	59,140
Held-to-maturity Securities, Continuous Unrealized Loss Position, Aggregate Loss1	-600	-2,057
Available-for-Sale and Held-to-Maturity:	'	'
Investment Securities in an Unrealized Loss Position (Number of Securities)	106	229
Obligations of U.S. government agencies	'	'
Available-for-Sale:	'	'
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	61,265	458,385
Available-for-sale Securities, Continuous Unrealized Loss Position, Less Than 12 months, Aggregate Loss1	-185	-10,355
Available-for-Sale, 12 Months or More Fair Value	353,997	59,362
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 months or Longer, Aggregate Loss1	-4,989	-1,894
Available-for-Sale, Total Fair Value	415,262	517,747
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Loss1	-5,174	-12,249
U.S. agency residential mortgage-backed securities & collateralized mortgage obligations	'	'
Available-for-Sale:	'	'
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	47,884	634,199
Available-for-sale Securities, Continuous Unrealized Loss Position, Less Than 12 months, Aggregate Loss1	-146	-17,273
Available-for-Sale, 12 Months or More Fair Value	203,157	166,930
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 months or Longer, Aggregate Loss1	-3,237	-7,874
Available-for-Sale, Total Fair Value	251,041	801,129
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Loss1	-3,383	-25,147
Private mortgage-backed securities	'	'
Available-for-Sale:	'	'
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than Twelve Months, Fair Value	0	0
Available-for-sale Securities, Continuous Unrealized Loss Position, Less Than 12 months, Aggregate Loss1	0	0
Available-for-Sale, 12 Months or More Fair Value	95	104
Available-for-sale Securities, Continuous Unrealized Loss Position, 12 months or Longer, Aggregate Loss1	-2	-1
Available-for-Sale, Total Fair Value	95	104
Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Loss1	-2	-1
State, county and municipal securities	'	'
Held-to-Maturity:	'	'
Held-to-Maturity, Less than 12 Months Fair Value	267	37,550
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less Than 12 months, Aggregate Loss1	-1	-1,319
Held-to-Maturity, 12 Months or More Fair Value	28,986	14,296
Held-to-Maturity, 12 Months or More Gross Unrealized Losses	-599	-730
Held-to-Maturity, Total Fair Value	29,253	51,846
Held-to-maturity Securities, Continuous Unrealized Loss Position, Aggregate Loss1	-600	-2,049
Corporate Debt Securities [Member]	'	'
Held-to-Maturity:	'	'
Held-to-Maturity, Less than 12 Months Fair Value	'	7,294
Held-to-maturity Securities, Continuous Unrealized Loss Position, Less Than 12 months, Aggregate Loss1	'	-8
Held-to-Maturity, 12 Months or More Fair Value	'	0
Held-to-Maturity, 12 Months or More Gross Unrealized Losses	'	0
Held-to-Maturity, Total Fair Value	'	7,294
Held-to-maturity Securities, Continuous Unrealized Loss Position, Aggregate Loss1	'	($8)

Maturities_of_Investment_Secur

Maturities of Investment Securities (Details) (USD $)	Jun. 30, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Available-for-sale Securities, Debt Maturities, Amortized Cost Basis, Rolling Maturity	'	'
Available-for-Sale Amortized Cost, Within One Year	$235,880	'
Available-for-Sale Amortized Cost, After One Year but Within Five Years	1,046,202	'
Available-for-Sale Amortized Cost, After Five Years but Within Ten Years	203,374	'
Available-for-Sale Amortized Cost, After Ten Years	15,580	'
Available-for-Sale, Amortized Cost	1,501,036	1,971,757
Available-for-sale Securities, Debt Maturities, Fair Value, Rolling Maturity	'	'
Available-for-Sale Estimated Fair Value, Within One Year	238,377	'
Available-for-Sale Estimated Fair Value, After One Year but Within Five Years	1,050,653	'
Available-for-Sale Estimated Fair Value, After Ten Years	202,197	'
Available-for-Sale Estimated Fair Value, After Five Years but Within Ten Years	15,769	'
Available-for-Sale, Estimated Fair Value	1,506,996	1,947,706
Held-to-maturity Securities, Debt Maturities, Net Carrying Amount	'	'
Held-to-Maturity Amortized Cost, Within One Year	75,137	'
Held-to-Maturity Amortized Cost, After One Year but Within Five Years	262,721	'
Held-to-Maturity Amortized Cost, After Five Years but Within Ten Years	174,980	'
Held-to-Maturity Amortized Cost, After Ten Years	74,151	'
Held-to-Maturity, Amortized Cost	586,989	203,837
Held-to-maturity Securities, Debt Maturities, Fair Value, Rolling Maturity	'	'
Held-to-Maturity Estimated Fair Value, Within One Year	75,805	'
Held-to-Maturity Estimated Fair Value, After One Year but Within Five Years	265,277	'
Held-to-Maturity Estimated Fair Value, After Five Years but Within Ten Years	176,267	'
Held-to-Maturity Estimated Fair Value, After Ten Years	75,333	'
Held-to-Maturity, Estimated Fair Value	592,682	205,926
Callable Within One Year	'	'
Available-for-sale Securities and Held-to-maturity Securities	'	'
Investment Securities Primarily Classified as Available-for-Sale, Amortized Costs, After One Year but Within Five Years	208,708	'
Investment Securities Primarily Classified as Available-for-Sale, Fair Value, After One Year but Within Five Years	208,188	'
Callable Structured Notes	'	'
Available-for-sale Securities and Held-to-maturity Securities	'	'
Investment Securities Primarily Classified as Available-for-Sale, Amortized Costs, After One Year but Within Five Years	94,473	'
Investment Securities Primarily Classified as Available-for-Sale, Fair Value, After One Year but Within Five Years	$94,487	'

Schedule_of_Loans_by_Class_Det

Schedule of Loans by Class (Details) (USD $)	Jun. 30, 2014	Dec. 31, 2013	Jun. 30, 2013
In Thousands, unless otherwise specified
Loans and Leases Receivable [Line Items]	'	'	'
Loans held for investment	$4,449,699	$4,303,992	'
Mortgage loans held for sale	56,663	40,861	'
Total loans	4,506,362	4,344,853	4,297,364
Commercial real estate	'	'	'
Loans and Leases Receivable [Line Items]	'	'	'
Loans held for investment	1,464,947	1,449,174	'
Land acquisition & development construction real estate	'	'	'
Loans and Leases Receivable [Line Items]	'	'	'
Loans held for investment	192,289	205,911	'
Residential construction real estate	'	'	'
Loans and Leases Receivable [Line Items]	'	'	'
Loans held for investment	82,121	76,488	'
Commercial construction real estate	'	'	'
Loans and Leases Receivable [Line Items]	'	'	'
Loans held for investment	86,599	69,236	'
Total construction loans	'	'	'
Loans and Leases Receivable [Line Items]	'	'	'
Loans held for investment	361,009	351,635	'
Residential real estate	'	'	'
Loans and Leases Receivable [Line Items]	'	'	'
Loans held for investment	894,502	867,912	'
Agricultural real estate	'	'	'
Loans and Leases Receivable [Line Items]	'	'	'
Loans held for investment	162,428	173,534	'
Total real estate loans	'	'	'
Loans and Leases Receivable [Line Items]	'	'	'
Loans held for investment	2,882,886	2,842,255	'
Indirect consumer	'	'	'
Loans and Leases Receivable [Line Items]	'	'	'
Loans held for investment	512,063	476,012	'
Other consumer	'	'	'
Loans and Leases Receivable [Line Items]	'	'	'
Loans held for investment	133,604	133,039	'
Credit card consumer	'	'	'
Loans and Leases Receivable [Line Items]	'	'	'
Loans held for investment	61,368	62,536	'
Total consumer loans	'	'	'
Loans and Leases Receivable [Line Items]	'	'	'
Loans held for investment	707,035	671,587	'
Commercial	'	'	'
Loans and Leases Receivable [Line Items]	'	'	'
Loans held for investment	727,482	676,544	'
Agricultural	'	'	'
Loans and Leases Receivable [Line Items]	'	'	'
Loans held for investment	130,280	111,872	'
Other, including overdrafts	'	'	'
Loans and Leases Receivable [Line Items]	'	'	'
Loans held for investment	$2,016	$1,734	'

Schedule_of_Recorded_Investmen

Schedule of Recorded Investment in Past Due Loans by Class (Details) (USD $)	3 Months Ended		6 Months Ended
In Thousands, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013	Dec. 31, 2013
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]	'	'	'	'	'
Mortgage loans held for sale	$56,663	'	$56,663	'	$40,861
Loans held for investment	4,449,699	'	4,449,699	'	4,303,992
Total loans	4,506,362	4,297,364	4,506,362	4,297,364	4,344,853
Interest Income on Non-Accrual Loans if Accrued	1,061	1,299	2,182	2,651	'
Commercial real estate	'	'	'	'	'
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]	'	'	'	'	'
30 to 59 Days Past Due	5,343	'	5,343	'	5,924
60 to 89 Days Past Due	2,540	'	2,540	'	2,472
Greater than 90 Days Past Due	40	'	40	'	22
Total Loans 30 or More Days Past Due	7,923	'	7,923	'	8,418
Current Loans	1,418,602	'	1,418,602	'	1,391,823
Non-accrual Loans	38,422	'	38,422	'	48,933
Loans held for investment	1,464,947	'	1,464,947	'	1,449,174
Land acquisition & development construction real estate	'	'	'	'	'
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]	'	'	'	'	'
30 to 59 Days Past Due	782	'	782	'	1,062
60 to 89 Days Past Due	123	'	123	'	468
Greater than 90 Days Past Due	0	'	0	'	38
Total Loans 30 or More Days Past Due	905	'	905	'	1,568
Current Loans	180,094	'	180,094	'	188,074
Non-accrual Loans	11,290	'	11,290	'	16,269
Loans held for investment	192,289	'	192,289	'	205,911
Residential construction real estate	'	'	'	'	'
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]	'	'	'	'	'
30 to 59 Days Past Due	90	'	90	'	933
60 to 89 Days Past Due	1,226	'	1,226	'	250
Greater than 90 Days Past Due	0	'	0	'	0
Total Loans 30 or More Days Past Due	1,316	'	1,316	'	1,183
Current Loans	80,152	'	80,152	'	73,933
Non-accrual Loans	653	'	653	'	1,372
Loans held for investment	82,121	'	82,121	'	76,488
Commercial construction real estate	'	'	'	'	'
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]	'	'	'	'	'
30 to 59 Days Past Due	0	'	0	'	584
60 to 89 Days Past Due	0	'	0	'	0
Greater than 90 Days Past Due	0	'	0	'	0
Total Loans 30 or More Days Past Due	0	'	0	'	584
Current Loans	84,019	'	84,019	'	68,427
Non-accrual Loans	2,580	'	2,580	'	225
Loans held for investment	86,599	'	86,599	'	69,236
Total construction loans	'	'	'	'	'
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]	'	'	'	'	'
30 to 59 Days Past Due	872	'	872	'	2,579
60 to 89 Days Past Due	1,349	'	1,349	'	718
Greater than 90 Days Past Due	0	'	0	'	38
Total Loans 30 or More Days Past Due	2,221	'	2,221	'	3,335
Current Loans	344,265	'	344,265	'	330,434
Non-accrual Loans	14,523	'	14,523	'	17,866
Loans held for investment	361,009	'	361,009	'	351,635
Residential real estate	'	'	'	'	'
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]	'	'	'	'	'
30 to 59 Days Past Due	3,493	'	3,493	'	3,630
60 to 89 Days Past Due	823	'	823	'	206
Greater than 90 Days Past Due	665	'	665	'	1,162
Total Loans 30 or More Days Past Due	4,981	'	4,981	'	4,998
Current Loans	884,261	'	884,261	'	856,800
Non-accrual Loans	5,260	'	5,260	'	6,114
Loans held for investment	894,502	'	894,502	'	867,912
Agricultural real estate	'	'	'	'	'
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]	'	'	'	'	'
30 to 59 Days Past Due	29	'	29	'	328
60 to 89 Days Past Due	72	'	72	'	646
Greater than 90 Days Past Due	0	'	0	'	0
Total Loans 30 or More Days Past Due	101	'	101	'	974
Current Loans	155,228	'	155,228	'	163,986
Non-accrual Loans	7,099	'	7,099	'	8,574
Loans held for investment	162,428	'	162,428	'	173,534
Total real estate loans	'	'	'	'	'
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]	'	'	'	'	'
30 to 59 Days Past Due	9,737	'	9,737	'	12,461
60 to 89 Days Past Due	4,784	'	4,784	'	4,042
Greater than 90 Days Past Due	705	'	705	'	1,222
Total Loans 30 or More Days Past Due	15,226	'	15,226	'	17,725
Current Loans	2,802,356	'	2,802,356	'	2,743,043
Non-accrual Loans	65,304	'	65,304	'	81,487
Loans held for investment	2,882,886	'	2,882,886	'	2,842,255
Indirect consumer	'	'	'	'	'
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]	'	'	'	'	'
30 to 59 Days Past Due	2,467	'	2,467	'	3,303
60 to 89 Days Past Due	404	'	404	'	430
Greater than 90 Days Past Due	15	'	15	'	9
Total Loans 30 or More Days Past Due	2,886	'	2,886	'	3,742
Current Loans	508,777	'	508,777	'	471,906
Non-accrual Loans	400	'	400	'	364
Loans held for investment	512,063	'	512,063	'	476,012
Other consumer	'	'	'	'	'
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]	'	'	'	'	'
30 to 59 Days Past Due	780	'	780	'	925
60 to 89 Days Past Due	210	'	210	'	130
Greater than 90 Days Past Due	16	'	16	'	1
Total Loans 30 or More Days Past Due	1,006	'	1,006	'	1,056
Current Loans	131,864	'	131,864	'	131,508
Non-accrual Loans	734	'	734	'	475
Loans held for investment	133,604	'	133,604	'	133,039
Credit card consumer	'	'	'	'	'
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]	'	'	'	'	'
30 to 59 Days Past Due	281	'	281	'	364
60 to 89 Days Past Due	239	'	239	'	187
Greater than 90 Days Past Due	335	'	335	'	515
Total Loans 30 or More Days Past Due	855	'	855	'	1,066
Current Loans	60,496	'	60,496	'	61,451
Non-accrual Loans	17	'	17	'	19
Loans held for investment	61,368	'	61,368	'	62,536
Total consumer loans	'	'	'	'	'
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]	'	'	'	'	'
30 to 59 Days Past Due	3,528	'	3,528	'	4,592
60 to 89 Days Past Due	853	'	853	'	747
Greater than 90 Days Past Due	366	'	366	'	525
Total Loans 30 or More Days Past Due	4,747	'	4,747	'	5,864
Current Loans	701,137	'	701,137	'	664,865
Non-accrual Loans	1,151	'	1,151	'	858
Loans held for investment	707,035	'	707,035	'	671,587
Commercial	'	'	'	'	'
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]	'	'	'	'	'
30 to 59 Days Past Due	3,223	'	3,223	'	2,791
60 to 89 Days Past Due	718	'	718	'	1,186
Greater than 90 Days Past Due	325	'	325	'	563
Total Loans 30 or More Days Past Due	4,266	'	4,266	'	4,540
Current Loans	710,886	'	710,886	'	660,035
Non-accrual Loans	12,330	'	12,330	'	11,969
Loans held for investment	727,482	'	727,482	'	676,544
Agricultural	'	'	'	'	'
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]	'	'	'	'	'
30 to 59 Days Past Due	1,390	'	1,390	'	453
60 to 89 Days Past Due	17	'	17	'	672
Greater than 90 Days Past Due	125	'	125	'	0
Total Loans 30 or More Days Past Due	1,532	'	1,532	'	1,125
Current Loans	128,367	'	128,367	'	110,622
Non-accrual Loans	381	'	381	'	125
Loans held for investment	130,280	'	130,280	'	111,872
Other, including overdrafts	'	'	'	'	'
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]	'	'	'	'	'
30 to 59 Days Past Due	0	'	0	'	0
60 to 89 Days Past Due	0	'	0	'	0
Greater than 90 Days Past Due	1	'	1	'	0
Total Loans 30 or More Days Past Due	1	'	1	'	0
Current Loans	2,015	'	2,015	'	1,734
Non-accrual Loans	0	'	0	'	0
Loans held for investment	2,016	'	2,016	'	1,734
Loans held for investment	'	'	'	'	'
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]	'	'	'	'	'
30 to 59 Days Past Due	17,878	'	17,878	'	20,297
60 to 89 Days Past Due	6,372	'	6,372	'	6,647
Greater than 90 Days Past Due	1,522	'	1,522	'	2,310
Total Loans 30 or More Days Past Due	25,772	'	25,772	'	29,254
Current Loans	4,344,761	'	4,344,761	'	4,180,299
Non-accrual Loans	79,166	'	79,166	'	94,439
Loans held for investment	4,449,699	'	4,449,699	'	4,303,992
Mortgage loans originated for sale	'	'	'	'	'
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]	'	'	'	'	'
30 to 59 Days Past Due	0	'	0	'	0
60 to 89 Days Past Due	0	'	0	'	0
Greater than 90 Days Past Due	0	'	0	'	0
Total Loans 30 or More Days Past Due	0	'	0	'	0
Current Loans	56,663	'	56,663	'	40,861
Non-accrual Loans	0	'	0	'	0
Total loans	'	'	'	'	'
Loans and Leases Receivable Recorded Investment, Past Due [Line Items]	'	'	'	'	'
30 to 59 Days Past Due	17,878	'	17,878	'	20,297
60 to 89 Days Past Due	6,372	'	6,372	'	6,647
Greater than 90 Days Past Due	1,522	'	1,522	'	2,310
Total Loans 30 or More Days Past Due	25,772	'	25,772	'	29,254
Current Loans	4,401,424	'	4,401,424	'	4,221,160
Non-accrual Loans	79,166	'	79,166	'	94,439
Total loans	$4,506,362	'	$4,506,362	'	$4,344,853

Loans_Schedule_of_Recorded_Inv

Loans Schedule of Recorded Investment in Impaired Loans (Details) (USD $)	3 Months Ended		6 Months Ended
In Thousands, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013	Dec. 31, 2013
Loans and Leases Receivable Recorded Investment, Impaired [Line Items]	'	'	'	'	'
Financing Receivable, Recorded Investment, Nonaccrual Status, Interest Income if Accrued	$1,061	$1,299	$2,182	$2,651	'
Impaired Financing Receivable, Unpaid Principal Balance	'	'	'	'	'
Unpaid Total Principal Balance	104,093	'	104,093	'	124,867
Recorded Investment With No Allowance	56,650	'	56,650	'	62,724
Recorded Investment With Allowance	37,752	'	37,752	'	47,848
Total Recorded Investment	94,402	'	94,402	'	110,572
Related Allowance	6,952	'	6,952	'	8,929
Impaired Financing Receivable, Average Recorded Investment and Cash Basis Method Interest Income	'	'	'	'	'
Average Recorded Investment	103,910	127,553	107,961	127,499	'
Income Recognized	300	318	555	1,127	'
Interest Income on Impaired Loans If Interest Had Been Accrued	1,301	1,577	2,412	2,912	'
Commercial real estate	'	'	'	'	'
Impaired Financing Receivable, Unpaid Principal Balance	'	'	'	'	'
Unpaid Total Principal Balance	52,690	'	52,690	'	64,780
Recorded Investment With No Allowance	24,961	'	24,961	'	29,216
Recorded Investment With Allowance	25,622	'	25,622	'	33,937
Total Recorded Investment	50,583	'	50,583	'	63,153
Related Allowance	3,566	'	3,566	'	5,210
Impaired Financing Receivable, Average Recorded Investment and Cash Basis Method Interest Income	'	'	'	'	'
Average Recorded Investment	57,588	67,605	60,870	67,192	'
Income Recognized	241	272	457	610	'
Land acquisition & development construction real estate	'	'	'	'	'
Impaired Financing Receivable, Unpaid Principal Balance	'	'	'	'	'
Unpaid Total Principal Balance	15,601	'	15,601	'	23,906
Recorded Investment With No Allowance	8,098	'	8,098	'	9,901
Recorded Investment With Allowance	3,869	'	3,869	'	7,226
Total Recorded Investment	11,967	'	11,967	'	17,127
Related Allowance	647	'	647	'	1,434
Impaired Financing Receivable, Average Recorded Investment and Cash Basis Method Interest Income	'	'	'	'	'
Average Recorded Investment	13,563	19,007	14,554	20,123	'
Income Recognized	11	15	22	456	'
Residential construction real estate	'	'	'	'	'
Impaired Financing Receivable, Unpaid Principal Balance	'	'	'	'	'
Unpaid Total Principal Balance	1,096	'	1,096	'	1,816
Recorded Investment With No Allowance	653	'	653	'	1,095
Recorded Investment With Allowance	0	'	0	'	277
Total Recorded Investment	653	'	653	'	1,372
Related Allowance	0	'	0	'	26
Impaired Financing Receivable, Average Recorded Investment and Cash Basis Method Interest Income	'	'	'	'	'
Average Recorded Investment	785	1,569	1,051	2,040	'
Income Recognized	0	0	0	0	'
Commercial construction real estate	'	'	'	'	'
Impaired Financing Receivable, Unpaid Principal Balance	'	'	'	'	'
Unpaid Total Principal Balance	2,749	'	2,749	'	397
Recorded Investment With No Allowance	269	'	269	'	279
Recorded Investment With Allowance	2,446	'	2,446	'	84
Total Recorded Investment	2,715	'	2,715	'	363
Related Allowance	908	'	908	'	85
Impaired Financing Receivable, Average Recorded Investment and Cash Basis Method Interest Income	'	'	'	'	'
Average Recorded Investment	1,471	6,346	918	7,118	'
Income Recognized	2	0	4	0	'
Total construction loans	'	'	'	'	'
Impaired Financing Receivable, Unpaid Principal Balance	'	'	'	'	'
Unpaid Total Principal Balance	19,446	'	19,446	'	26,119
Recorded Investment With No Allowance	9,020	'	9,020	'	11,275
Recorded Investment With Allowance	6,315	'	6,315	'	7,587
Total Recorded Investment	15,335	'	15,335	'	18,862
Related Allowance	1,555	'	1,555	'	1,545
Impaired Financing Receivable, Average Recorded Investment and Cash Basis Method Interest Income	'	'	'	'	'
Average Recorded Investment	15,819	26,922	16,523	29,281	'
Income Recognized	13	15	26	456	'
Residential real estate	'	'	'	'	'
Impaired Financing Receivable, Unpaid Principal Balance	'	'	'	'	'
Unpaid Total Principal Balance	7,222	'	7,222	'	9,448
Recorded Investment With No Allowance	4,885	'	4,885	'	5,081
Recorded Investment With Allowance	375	'	375	'	967
Total Recorded Investment	5,260	'	5,260	'	6,048
Related Allowance	301	'	301	'	249
Impaired Financing Receivable, Average Recorded Investment and Cash Basis Method Interest Income	'	'	'	'	'
Average Recorded Investment	5,852	8,311	5,969	9,429	'
Income Recognized	1	5	3	9	'
Agricultural real estate	'	'	'	'	'
Impaired Financing Receivable, Unpaid Principal Balance	'	'	'	'	'
Unpaid Total Principal Balance	9,191	'	9,191	'	8,895
Recorded Investment With No Allowance	6,656	'	6,656	'	6,429
Recorded Investment With Allowance	2,439	'	2,439	'	2,370
Total Recorded Investment	9,095	'	9,095	'	8,799
Related Allowance	133	'	133	'	335
Impaired Financing Receivable, Average Recorded Investment and Cash Basis Method Interest Income	'	'	'	'	'
Average Recorded Investment	9,747	8,255	9,830	6,611	'
Income Recognized	25	4	29	8	'
Total real estate loans	'	'	'	'	'
Impaired Financing Receivable, Unpaid Principal Balance	'	'	'	'	'
Unpaid Total Principal Balance	88,549	'	88,549	'	109,242
Recorded Investment With No Allowance	45,522	'	45,522	'	52,001
Recorded Investment With Allowance	34,751	'	34,751	'	44,861
Total Recorded Investment	80,273	'	80,273	'	96,862
Related Allowance	5,555	'	5,555	'	7,339
Impaired Financing Receivable, Average Recorded Investment and Cash Basis Method Interest Income	'	'	'	'	'
Average Recorded Investment	89,006	111,093	93,192	112,513	'
Income Recognized	280	296	515	1,083	'
Commercial	'	'	'	'	'
Impaired Financing Receivable, Unpaid Principal Balance	'	'	'	'	'
Unpaid Total Principal Balance	14,752	'	14,752	'	15,448
Recorded Investment With No Allowance	10,709	'	10,709	'	10,684
Recorded Investment With Allowance	2,679	'	2,679	'	2,901
Total Recorded Investment	13,388	'	13,388	'	13,585
Related Allowance	1,176	'	1,176	'	1,504
Impaired Financing Receivable, Average Recorded Investment and Cash Basis Method Interest Income	'	'	'	'	'
Average Recorded Investment	14,162	16,087	14,231	14,484	'
Income Recognized	14	18	28	36	'
Agricultural	'	'	'	'	'
Impaired Financing Receivable, Unpaid Principal Balance	'	'	'	'	'
Unpaid Total Principal Balance	792	'	792	'	177
Recorded Investment With No Allowance	419	'	419	'	39
Recorded Investment With Allowance	322	'	322	'	86
Total Recorded Investment	741	'	741	'	125
Related Allowance	221	'	221	'	86
Impaired Financing Receivable, Average Recorded Investment and Cash Basis Method Interest Income	'	'	'	'	'
Average Recorded Investment	742	373	538	502	'
Income Recognized	$6	$4	$12	$8	'

Schedule_of_Loans_Renegotiated

Schedule of Loans Renegotiated in Troubled Debt Restructurings (Details) (USD $)	3 Months Ended		6 Months Ended
In Thousands, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Dec. 31, 2013
	notes		notes
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]	'	'	'	'
Loans Renegotiated in Troubled Debt Restructurings	$57,835	'	$57,835	$59,792
Loans Renegotiated in Troubled Debt Restructurings, Non-Accrual Loans	34,304	'	34,304	38,011
Loans Renegotiated in Troubled Debt Restructurings, Accrual Loans	23,531	'	23,531	21,781
Number of Notes	6	'	12	'
Financing Receivable, Modifications, Pre-Modification Recorded Investment	1,435	'	4,407	'
Financing Receivables, Impaired, Troubled Debt Restructuring, Write-down	0	0	0	'
Financing Receivable, Modifications, Subsequent Default, Number of Contracts	2	'	2	'
Financing Receivable, Modifications, Subsequent Default, Recorded Investment	72	'	72	'
Loans and Leases Receivable, Impaired, Commitment to Lend	0	'	0	'
Interest only period	'	'	'	'
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]	'	'	'	'
Financing Receivable, Modifications, Pre-Modification Recorded Investment	530	'	299	'
Extension of terms or maturity	'	'	'	'
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]	'	'	'	'
Financing Receivable, Modifications, Pre-Modification Recorded Investment	226	'	3,157	'
Interest rate adjustment	'	'	'	'
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]	'	'	'	'
Financing Receivable, Modifications, Pre-Modification Recorded Investment	0	'	0	'
Other	'	'	'	'
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]	'	'	'	'
Financing Receivable, Modifications, Pre-Modification Recorded Investment	679	'	951	'
Commercial real estate	'	'	'	'
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]	'	'	'	'
Number of Notes	4	'	8	'
Financing Receivable, Modifications, Pre-Modification Recorded Investment	1,363	'	1,147	'
Commercial real estate | Interest only period	'	'	'	'
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]	'	'	'	'
Financing Receivable, Modifications, Pre-Modification Recorded Investment	458	'	0	'
Commercial real estate | Extension of terms or maturity	'	'	'	'
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]	'	'	'	'
Financing Receivable, Modifications, Pre-Modification Recorded Investment	226	'	226	'
Commercial real estate | Interest rate adjustment	'	'	'	'
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]	'	'	'	'
Financing Receivable, Modifications, Pre-Modification Recorded Investment	0	'	0	'
Commercial real estate | Other	'	'	'	'
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]	'	'	'	'
Financing Receivable, Modifications, Pre-Modification Recorded Investment	679	'	921	'
Commercial	'	'	'	'
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]	'	'	'	'
Number of Notes	0	'	4	'
Financing Receivable, Modifications, Pre-Modification Recorded Investment	72	'	3,260	'
Financing Receivable, Modifications, Subsequent Default, Number of Contracts	2	'	'	'
Financing Receivable, Modifications, Subsequent Default, Recorded Investment	72	'	72	'
Commercial | Interest only period	'	'	'	'
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]	'	'	'	'
Financing Receivable, Modifications, Pre-Modification Recorded Investment	72	'	299	'
Commercial | Extension of terms or maturity	'	'	'	'
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]	'	'	'	'
Financing Receivable, Modifications, Pre-Modification Recorded Investment	0	'	2,931	'
Commercial | Interest rate adjustment	'	'	'	'
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]	'	'	'	'
Financing Receivable, Modifications, Pre-Modification Recorded Investment	0	'	0	'
Commercial | Other	'	'	'	'
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]	'	'	'	'
Financing Receivable, Modifications, Pre-Modification Recorded Investment	$0	'	$30	'
Commercial	'	'	'	'
Loans and Leases Receivable, Troubled Debt Restructuring [Line Items]	'	'	'	'
Financing Receivable, Modifications, Subsequent Default, Number of Contracts	'	'	0	'

Schedule_of_Recorded_Investmen1

Schedule of Recorded Investment in Criticized Loans by Class and Credit Quality Indicator (Details) (USD $)	Jun. 30, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]	'	'
Loans held for investment	$4,449,699	$4,303,992
Commercial real estate	'	'
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]	'	'
Loans held for investment	1,464,947	1,449,174
Land acquisition & development construction real estate	'	'
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]	'	'
Loans held for investment	192,289	205,911
Residential construction real estate	'	'
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]	'	'
Loans held for investment	82,121	76,488
Commercial construction real estate	'	'
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]	'	'
Loans held for investment	86,599	69,236
Total construction loans	'	'
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]	'	'
Loans held for investment	361,009	351,635
Residential real estate	'	'
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]	'	'
Loans held for investment	894,502	867,912
Agricultural real estate	'	'
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]	'	'
Loans held for investment	162,428	173,534
Total real estate loans	'	'
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]	'	'
Loans held for investment	2,882,886	2,842,255
Indirect consumer	'	'
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]	'	'
Loans held for investment	512,063	476,012
Other consumer	'	'
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]	'	'
Loans held for investment	133,604	133,039
Credit card consumer	'	'
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]	'	'
Loans held for investment	61,368	62,536
Total consumer loans	'	'
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]	'	'
Loans held for investment	707,035	671,587
Commercial	'	'
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]	'	'
Loans held for investment	727,482	676,544
Agricultural	'	'
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]	'	'
Loans held for investment	130,280	111,872
Other Assets Especially Mentioned	'	'
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]	'	'
Loans held for investment	160,271	159,081
Other Assets Especially Mentioned | Commercial real estate	'	'
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]	'	'
Loans held for investment	81,539	79,747
Other Assets Especially Mentioned | Land acquisition & development construction real estate	'	'
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]	'	'
Loans held for investment	12,580	13,211
Other Assets Especially Mentioned | Residential construction real estate	'	'
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]	'	'
Loans held for investment	2,190	1,859
Other Assets Especially Mentioned | Commercial construction real estate	'	'
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]	'	'
Loans held for investment	186	0
Other Assets Especially Mentioned | Total construction loans	'	'
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]	'	'
Loans held for investment	14,956	15,070
Other Assets Especially Mentioned | Residential real estate	'	'
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]	'	'
Loans held for investment	11,028	7,500
Other Assets Especially Mentioned | Agricultural real estate	'	'
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]	'	'
Loans held for investment	9,638	13,597
Other Assets Especially Mentioned | Total real estate loans	'	'
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]	'	'
Loans held for investment	117,161	115,914
Other Assets Especially Mentioned | Indirect consumer	'	'
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]	'	'
Loans held for investment	769	875
Other Assets Especially Mentioned | Other consumer	'	'
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]	'	'
Loans held for investment	529	573
Other Assets Especially Mentioned | Credit card consumer	'	'
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]	'	'
Loans held for investment	0	0
Other Assets Especially Mentioned | Total consumer loans	'	'
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]	'	'
Loans held for investment	1,298	1,448
Other Assets Especially Mentioned | Commercial	'	'
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]	'	'
Loans held for investment	30,522	33,318
Other Assets Especially Mentioned | Agricultural	'	'
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]	'	'
Loans held for investment	11,290	8,401
Substandard	'	'
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]	'	'
Loans held for investment	155,744	154,100
Substandard | Commercial real estate	'	'
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]	'	'
Loans held for investment	82,558	86,426
Substandard | Land acquisition & development construction real estate	'	'
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]	'	'
Loans held for investment	13,053	19,677
Substandard | Residential construction real estate	'	'
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]	'	'
Loans held for investment	1,788	1,649
Substandard | Commercial construction real estate	'	'
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]	'	'
Loans held for investment	269	409
Substandard | Total construction loans	'	'
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]	'	'
Loans held for investment	15,110	21,735
Substandard | Residential real estate	'	'
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]	'	'
Loans held for investment	9,017	7,188
Substandard | Agricultural real estate	'	'
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]	'	'
Loans held for investment	15,755	10,245
Substandard | Total real estate loans	'	'
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]	'	'
Loans held for investment	122,440	125,594
Substandard | Indirect consumer	'	'
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]	'	'
Loans held for investment	1,575	1,524
Substandard | Other consumer	'	'
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]	'	'
Loans held for investment	927	969
Substandard | Credit card consumer	'	'
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]	'	'
Loans held for investment	390	392
Substandard | Total consumer loans	'	'
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]	'	'
Loans held for investment	2,892	2,885
Substandard | Commercial	'	'
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]	'	'
Loans held for investment	26,203	23,833
Substandard | Agricultural	'	'
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]	'	'
Loans held for investment	4,209	1,788
Doubtful	'	'
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]	'	'
Loans held for investment	29,115	45,308
Doubtful | Commercial real estate	'	'
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]	'	'
Loans held for investment	15,371	24,840
Doubtful | Land acquisition & development construction real estate	'	'
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]	'	'
Loans held for investment	2,626	7,329
Doubtful | Residential construction real estate	'	'
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]	'	'
Loans held for investment	0	277
Doubtful | Commercial construction real estate	'	'
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]	'	'
Loans held for investment	2,446	84
Doubtful | Total construction loans	'	'
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]	'	'
Loans held for investment	5,072	7,690
Doubtful | Residential real estate	'	'
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]	'	'
Loans held for investment	588	4,184
Doubtful | Agricultural real estate	'	'
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]	'	'
Loans held for investment	2,439	2,370
Doubtful | Total real estate loans	'	'
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]	'	'
Loans held for investment	23,470	39,084
Doubtful | Indirect consumer	'	'
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]	'	'
Loans held for investment	133	115
Doubtful | Other consumer	'	'
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]	'	'
Loans held for investment	398	268
Doubtful | Credit card consumer	'	'
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]	'	'
Loans held for investment	1,219	2,010
Doubtful | Total consumer loans	'	'
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]	'	'
Loans held for investment	1,750	2,393
Doubtful | Commercial	'	'
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]	'	'
Loans held for investment	3,573	3,745
Doubtful | Agricultural	'	'
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]	'	'
Loans held for investment	322	86
Total Criticized Loans	'	'
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]	'	'
Loans held for investment	345,130	358,489
Total Criticized Loans | Commercial real estate	'	'
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]	'	'
Loans held for investment	179,468	191,013
Total Criticized Loans | Land acquisition & development construction real estate	'	'
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]	'	'
Loans held for investment	28,259	40,217
Total Criticized Loans | Residential construction real estate	'	'
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]	'	'
Loans held for investment	3,978	3,785
Total Criticized Loans | Commercial construction real estate	'	'
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]	'	'
Loans held for investment	2,901	493
Total Criticized Loans | Total construction loans	'	'
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]	'	'
Loans held for investment	35,138	44,495
Total Criticized Loans | Residential real estate	'	'
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]	'	'
Loans held for investment	20,633	18,872
Total Criticized Loans | Agricultural real estate	'	'
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]	'	'
Loans held for investment	27,832	26,212
Total Criticized Loans | Total real estate loans	'	'
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]	'	'
Loans held for investment	263,071	280,592
Total Criticized Loans | Indirect consumer	'	'
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]	'	'
Loans held for investment	2,477	2,514
Total Criticized Loans | Other consumer	'	'
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]	'	'
Loans held for investment	1,854	1,810
Total Criticized Loans | Credit card consumer	'	'
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]	'	'
Loans held for investment	1,609	2,402
Total Criticized Loans | Total consumer loans	'	'
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]	'	'
Loans held for investment	5,940	6,726
Total Criticized Loans | Commercial	'	'
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]	'	'
Loans held for investment	60,298	60,896
Total Criticized Loans | Agricultural	'	'
Loans and Leases Receivable Recorded Investment, Criticized Loans [Line Items]	'	'
Loans held for investment	$15,821	$10,275

Schedule_of_Allowance_for_Loan

Schedule of Allowance for Loan Losses by Portfolio Segment (Details) (USD $)	3 Months Ended		6 Months Ended
In Thousands, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013	Dec. 31, 2013
Allowance for Loan and Lease Losses [Roll Forward]	'	'	'	'	'
Beginning balance	$81,371	$97,904	$85,339	$100,511	'
Provision charged to operating expense	-2,001	375	-7,001	875	'
Less loans charged-off	-2,626	-3,895	-5,417	-9,915	'
Add back recoveries of loans previously charged-off	1,522	4,144	5,345	7,057	'
Ending balance	78,266	98,528	78,266	98,528	'
Allowance for loan losses:	'	'	'	'	'
Loans individually evaluated for impairment	6,952	15,494	6,952	15,494	'
Loans collectively evaluated for impairment	71,314	83,034	71,314	83,034	'
Ending balance	78,266	98,528	78,266	98,528	'
Total loans:	'	'	'	'	'
Individually evaluated for impairment	94,402	124,090	94,402	124,090	'
Individually evaluated for impairment	4,411,960	4,173,274	4,411,960	4,173,274	'
Total loans	4,506,362	4,297,364	4,506,362	4,297,364	4,344,853
Real Estate	'	'	'	'	'
Allowance for Loan and Lease Losses [Roll Forward]	'	'	'	'	'
Beginning balance	59,830	71,666	63,923	75,782	'
Provision charged to operating expense	-2,011	-1,009	-5,386	-2,044	'
Less loans charged-off	-1,158	-2,027	-2,243	-6,170	'
Add back recoveries of loans previously charged-off	651	2,873	1,018	3,935	'
Ending balance	57,312	71,503	57,312	71,503	'
Allowance for loan losses:	'	'	'	'	'
Loans individually evaluated for impairment	5,555	10,267	5,555	10,267	'
Loans collectively evaluated for impairment	51,757	61,236	51,757	61,236	'
Ending balance	57,312	71,503	57,312	71,503	'
Total loans:	'	'	'	'	'
Individually evaluated for impairment	80,273	107,241	80,273	107,241	'
Individually evaluated for impairment	2,859,276	2,732,400	2,859,276	2,732,400	'
Total loans	2,939,549	2,839,641	2,939,549	2,839,641	'
Consumer	'	'	'	'	'
Allowance for Loan and Lease Losses [Roll Forward]	'	'	'	'	'
Beginning balance	5,377	7,088	6,193	7,140	'
Provision charged to operating expense	346	579	-232	1,116	'
Less loans charged-off	-934	-1,299	-1,780	-2,361	'
Add back recoveries of loans previously charged-off	558	672	1,166	1,145	'
Ending balance	5,347	7,040	5,347	7,040	'
Allowance for loan losses:	'	'	'	'	'
Loans individually evaluated for impairment	0	0	0	0	'
Loans collectively evaluated for impairment	5,347	7,040	5,347	7,040	'
Ending balance	5,347	7,040	5,347	7,040	'
Total loans:	'	'	'	'	'
Individually evaluated for impairment	0	0	0	0	'
Individually evaluated for impairment	707,035	652,944	707,035	652,944	'
Total loans	707,035	652,944	707,035	652,944	'
Commercial	'	'	'	'	'
Allowance for Loan and Lease Losses [Roll Forward]	'	'	'	'	'
Beginning balance	15,701	18,670	14,747	17,085	'
Provision charged to operating expense	-494	778	-1,566	1,799	'
Less loans charged-off	-534	-569	-1,330	-1,380	'
Add back recoveries of loans previously charged-off	313	596	3,135	1,971	'
Ending balance	14,986	19,475	14,986	19,475	'
Allowance for loan losses:	'	'	'	'	'
Loans individually evaluated for impairment	1,176	5,205	1,176	5,205	'
Loans collectively evaluated for impairment	13,810	14,270	13,810	14,270	'
Ending balance	14,986	19,475	14,986	19,475	'
Total loans:	'	'	'	'	'
Individually evaluated for impairment	13,388	16,710	13,388	16,710	'
Individually evaluated for impairment	714,094	666,539	714,094	666,539	'
Total loans	727,482	683,249	727,482	683,249	'
Agriculture	'	'	'	'	'
Allowance for Loan and Lease Losses [Roll Forward]	'	'	'	'	'
Beginning balance	463	480	476	504	'
Provision charged to operating expense	158	27	183	4	'
Less loans charged-off	0	0	-64	-4	'
Add back recoveries of loans previously charged-off	0	3	26	6	'
Ending balance	621	510	621	510	'
Allowance for loan losses:	'	'	'	'	'
Loans individually evaluated for impairment	221	22	221	22	'
Loans collectively evaluated for impairment	400	488	400	488	'
Ending balance	621	510	621	510	'
Total loans:	'	'	'	'	'
Individually evaluated for impairment	741	139	741	139	'
Individually evaluated for impairment	129,539	121,391	129,539	121,391	'
Total loans	130,280	121,530	130,280	121,530	'
Other	'	'	'	'	'
Allowance for Loan and Lease Losses [Roll Forward]	'	'	'	'	'
Beginning balance	0	0	0	0	'
Provision charged to operating expense	0	0	0	0	'
Less loans charged-off	0	0	0	0	'
Add back recoveries of loans previously charged-off	0	0	0	0	'
Ending balance	0	0	0	0	'
Allowance for loan losses:	'	'	'	'	'
Loans individually evaluated for impairment	0	0	0	0	'
Loans collectively evaluated for impairment	0	0	0	0	'
Ending balance	0	0	0	0	'
Total loans:	'	'	'	'	'
Individually evaluated for impairment	0	0	0	0	'
Individually evaluated for impairment	2,016	0	2,016	0	'
Total loans	$2,016	$0	$2,016	$0	'

OREO_Details

OREO (Details) (USD $)	3 Months Ended		6 Months Ended
In Thousands, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Real Estate Acquired Through Foreclosure [Roll Forward]	'	'	'	'
Beginning balance	$16,594	$32,470	$15,504	$32,571
Additions	984	3,224	4,399	8,555
Capitalized improvements	0	3	0	13
Valuation adjustments	-10	-259	-10	-2,564
Dispositions	-1,143	-12,656	-3,468	-15,793
Ending balance	$16,425	$22,782	$16,425	$22,782

Capital_Stock_Details

Capital Stock (Details) (USD $)	6 Months Ended				0 Months Ended
In Thousands, except Share data, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Dec. 31, 2013	Jan. 24, 2014	Jun. 30, 2014	Jun. 30, 2014	Dec. 31, 2013
			Class A Common Stock	Class A Common Stock	Class A Common Stock	Class A Common Stock	Class B Common Stock	Class B Common Stock
					2006 Equity Compensation Plan [Member]	Share Repurchase Program [Domain]
Class of Stock [Line Items]	'	'	'	'	'	'	'	'
Common Stock, Shares, Outstanding	'	'	20,269,171	19,868,018	'	'	23,985,841	24,287,045
Stock Repurchased and Retired During Period, Shares	'	'	325,418	'	'	'	'	'
Payments for Repurchase of Common Stock	$8,764	$448	$8,143	'	'	'	'	'
Stock Repurchase Program, Remaining Authorized Repurchase Amount	'	'	'	'	'	1,674,582	'	'
Share-based Compensation Arrangement by Share-based Payment Award, Number of Additional Shares Authorized	'	'	'	'	1,500,000	'	'	'

Computation_of_Basic_and_Dilut

Computation of Basic and Diluted Earnings per Share (Details) (USD $)	3 Months Ended		6 Months Ended
In Thousands, except Share data, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Net Income (Loss) Available to Common Stockholders, Basic	'	'	'	'
Net income	$21,077	$21,505	$42,470	$41,549
Weighted Average Number of Shares Outstanding, Basic and Diluted	'	'	'	'
Weighted average common shares outstanding for basic earnings per share computation	44,044,260	43,480,502	44,021,166	43,335,682
Dilutive effect of stock-based compensation	531,703	427,785	572,689	376,978
Weighted average common shares outstanding for diluted earnings per common share computation	44,575,963	43,908,287	44,593,855	43,712,660
Earnings Per Share, Basic and Diluted	'	'	'	'
Basic earnings per common share	$0.48	$0.49	$0.96	$0.96
Diluted earnings per common share	$0.47	$0.49	$0.95	$0.95
Stock Options	'	'	'	'
Earnings Per Share, Basic and Diluted [Line Items]	'	'	'	'
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	'	'	0	976,063
Unvested Restricted Stock	'	'	'	'
Earnings Per Share, Basic and Diluted [Line Items]	'	'	'	'
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount	'	'	107,651	56,668

Schedule_of_Actual_Capital_Amo

Schedule of Actual Capital Amounts and Ratios and Selected Minimum Regulatory Thresholds (Details) (USD $)	Jun. 30, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Total risk-based capital:	'	'
Actual Amount	$850,614	$829,443
Actual Ratio	16.70%	16.80%
Adequately Capitalized Amount	407,804	396,210
Adequately Capitalized Ratio	8.00%	8.00%
Tier 1 risk-based capital:	'	'
Actual Amount	765,715	739,246
Actual Ratio	15.00%	14.90%
Adequately Capitalized Amount	203,902	198,105
Adequately Capitalized Ratio	4.00%	4.00%
Leverage capital ratio:	'	'
Actual Amount	765,715	'
Actual Ratio	10.40%	10.10%
Adequately Capitalized Amount	295,843	293,414
Adequately Capitalized Ratio	4.00%	4.00%
FIB	'	'
Total risk-based capital:	'	'
Actual Amount	740,815	723,955
Actual Ratio	14.60%	14.70%
Adequately Capitalized Amount	406,334	394,038
Adequately Capitalized Ratio	8.00%	8.00%
Well Capitalized Amount	507,917	492,548
Well Capitalized Ratio	10.00%	10.00%
Tier 1 risk-based capital:	'	'
Actual Amount	668,143	650,093
Actual Ratio	13.20%	13.20%
Adequately Capitalized Amount	203,167	197,019
Adequately Capitalized Ratio	4.00%	4.00%
Well Capitalized Amount	304,750	295,529
Well Capitalized Ratio	6.00%	6.00%
Leverage capital ratio:	'	'
Actual Amount	668,143	'
Actual Ratio	9.10%	8.90%
Adequately Capitalized Amount	295,201	292,199
Adequately Capitalized Ratio	4.00%	4.00%
Well Capitalized Amount	$369,002	$365,248
Well Capitalized Ratio	5.00%	5.00%

Commitments_and_Contingencies_

Commitments and Contingencies (Details) (Construction Contracts, USD $)	Jun. 30, 2014
In Thousands, unless otherwise specified
Construction Contracts	'
Unrecorded Unconditional Purchase Obligation [Line Items]	'
Commitments to Purchase	$1,409

Financial_Instruments_with_Off1

Financial Instruments with Off-Balance Sheet Risk (Details) (USD $)	Jun. 30, 2014
In Thousands, unless otherwise specified
Entity Information [Line Items]	'
Credit Extension Commitments	$1,346,196
Credit Extension Commitments, Beyond One Year	334,981
Standby Letters of Credit	'
Entity Information [Line Items]	'
Credit Extension Commitments	65,133
Unused Credit Card Lines	'
Entity Information [Line Items]	'
Credit Extension Commitments	$447,827

Supplemental_Cash_Flow_Informa

Supplemental Cash Flow Information (Details) (USD $)	6 Months Ended
In Thousands, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013
Supplemental Cash Flow Information [Abstract]	'	'
Transferred Loans to OREO	$4,399	$8,555
Transferred Loans to Mortgage Servicing Assets	1,024	2,149
Transfer from Investments	'	429
Land and buildings transferred to other assets	'	$1,448

Schedule_of_Comprehensive_Inco

Schedule of Comprehensive Income (Loss) (Details) (USD $)	3 Months Ended		6 Months Ended
In Thousands, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Change in net unrealized Gain during period:	'	'	'	'
Change in net unrealized gain during period, before tax amount	$2,816	($35,625)	$17,167	($41,342)
Change in net unrealized gain during period, tax expense (benefit)	1,108	-14,018	6,755	-16,268
Change in net unrealized gain during period, net of tax amount	1,708	-21,607	10,412	-25,074
Reclassification adjustment for gains included in net income:	'	'	'	'
Reclassification adjustment for gains included in net income, before tax amount	-17	12	-88	4
Reclassification adjustment for gains included in net income, tax expense (benefit)	-7	5	-35	2
Reclassification adjustment for gains included in net income, net of tax amount	-10	7	-53	2
Change in net actuarial loss:	'	'	'	'
Change in net actuarial loss, before tax amount	35	35	70	70
Change in net actuarial loss, tax expense (benefit)	14	14	28	28
Change in net actuarial loss, net of tax amount	21	21	42	42
Other comprehensive income (loss):	'	'	'	'
Other comprehensive income (loss), before tax	2,834	-35,578	17,149	-41,268
Total other comprehensive income, tax expense (benefit)	1,115	-13,999	6,748	-16,238
Total other comprehensive income, net of tax amount	$1,719	($21,579)	$10,401	($25,030)

Schedule_of_Accumulated_Other_

Schedule of Accumulated Other Comprehensive Income (Loss) (Details) (USD $)	Jun. 30, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Net accumulated other comprehensive income:	'	'
Net unrealized gain on investment securities available-for-sale	($4,219)	($14,578)
Net actuarial loss on defined benefit post-retirement benefit plans	-1,421	-1,463
Net accumulated other comprehensive income	($5,640)	($16,041)

Schedule_of_Financial_Assets_a

Schedule of Financial Assets and Financial Liabilities Measured at Fair Value on a Recurring and Non-Recurring Basis (Details) (USD $)	3 Months Ended		6 Months Ended
In Thousands, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013	Dec. 31, 2013
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'	'	'	'
Real Estate Acquired Through Foreclosure, Valuation Adjustments	$10	$259	$10	$2,564	'
Related Allowance	6,952	'	6,952	'	8,929
Quoted Prices in Active Markets for Identical Assets (Level 1) | Fair Value Measured on a Recurring Basis	'	'	'	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'	'	'	'
Mortgage servicing rights	0	'	0	'	0
Quoted Prices in Active Markets for Identical Assets (Level 1) | Fair Value Measured on a Non-recurring Basis	'	'	'	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'	'	'	'
Impaired loans	0	'	0	'	0
Other real estate owned	0	'	0	'	0
Long-lived assets to be disposed of by sale	0	'	0	'	0
Significant Other Observable Inputs (Level 2) | Fair Value Measured on a Recurring Basis	'	'	'	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'	'	'	'
Mortgage servicing rights	25,812	'	25,812	'	25,698
Significant Other Observable Inputs (Level 2) | Fair Value Measured on a Non-recurring Basis	'	'	'	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'	'	'	'
Impaired loans	0	'	0	'	0
Other real estate owned	0	'	0	'	0
Long-lived assets to be disposed of by sale	0	'	0	'	0
Significant Unobservable Inputs (Level 3) | Fair Value Measured on a Recurring Basis	'	'	'	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'	'	'	'
Mortgage servicing rights	0	'	0	'	0
Significant Unobservable Inputs (Level 3) | Fair Value Measured on a Non-recurring Basis	'	'	'	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'	'	'	'
Impaired loans	46,505	'	46,505	'	57,302
Real Estate Acquired Through Foreclosure, Valuation Adjustments	'	'	10	2,564	'
Impairment of real estate, received updated appraisal	'	'	'	196	'
Other real estate owned	6,895	'	6,895	'	8,502
Long-lived assets to be disposed of by sale	1,186	'	1,186	'	1,186
Related Allowance	6,952	'	6,952	'	8,929
Impaired Financing Receivable, Related Allowance, Partial Loan Charge-Offs	9,692	'	9,692	'	14,295
Impairment of Real Estate, Change in Management Estimates	'	'	'	2,368	'
Estimated Fair Value | Fair Value Measured on a Recurring Basis	'	'	'	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'	'	'	'
Mortgage servicing rights	25,812	'	25,812	'	25,698
Estimated Fair Value | Fair Value Measured on a Non-recurring Basis	'	'	'	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'	'	'	'
Impaired loans	46,505	'	46,505	'	57,302
Other real estate owned	6,895	'	6,895	'	8,502
Long-lived assets to be disposed of by sale	1,186	'	1,186	'	1,186
Change During Period | Fair Value Measured on a Non-recurring Basis	'	'	'	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'	'	'	'
Long-lived assets to be disposed of by sale	599	'	599	'	'
Obligations of U.S. government agencies | Quoted Prices in Active Markets for Identical Assets (Level 1) | Fair Value Measured on a Recurring Basis	'	'	'	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'	'	'	'
Investment securities available-for-sale	0	'	0	'	0
Obligations of U.S. government agencies | Significant Other Observable Inputs (Level 2) | Fair Value Measured on a Recurring Basis	'	'	'	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'	'	'	'
Investment securities available-for-sale	718,567	'	718,567	'	763,238
Obligations of U.S. government agencies | Significant Unobservable Inputs (Level 3) | Fair Value Measured on a Recurring Basis	'	'	'	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'	'	'	'
Investment securities available-for-sale	0	'	0	'	0
Obligations of U.S. government agencies | Estimated Fair Value | Fair Value Measured on a Recurring Basis	'	'	'	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'	'	'	'
Investment securities available-for-sale	718,567	'	718,567	'	763,238
U.S. agency residential mortgage-backed securities & collateralized mortgage obligations | Quoted Prices in Active Markets for Identical Assets (Level 1) | Fair Value Measured on a Recurring Basis	'	'	'	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'	'	'	'
Investment securities available-for-sale	0	'	0	'	0
U.S. agency residential mortgage-backed securities & collateralized mortgage obligations | Significant Other Observable Inputs (Level 2) | Fair Value Measured on a Recurring Basis	'	'	'	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'	'	'	'
Investment securities available-for-sale	788,064	'	788,064	'	1,184,053
U.S. agency residential mortgage-backed securities & collateralized mortgage obligations | Significant Unobservable Inputs (Level 3) | Fair Value Measured on a Recurring Basis	'	'	'	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'	'	'	'
Investment securities available-for-sale	0	'	0	'	0
U.S. agency residential mortgage-backed securities & collateralized mortgage obligations | Estimated Fair Value | Fair Value Measured on a Recurring Basis	'	'	'	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'	'	'	'
Investment securities available-for-sale	788,064	'	788,064	'	1,184,053
Private mortgage-backed securities | Quoted Prices in Active Markets for Identical Assets (Level 1) | Fair Value Measured on a Recurring Basis	'	'	'	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'	'	'	'
Investment securities available-for-sale	0	'	0	'	0
Private mortgage-backed securities | Significant Other Observable Inputs (Level 2) | Fair Value Measured on a Recurring Basis	'	'	'	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'	'	'	'
Investment securities available-for-sale	365	'	365	'	415
Private mortgage-backed securities | Significant Unobservable Inputs (Level 3) | Fair Value Measured on a Recurring Basis	'	'	'	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'	'	'	'
Investment securities available-for-sale	0	'	0	'	0
Private mortgage-backed securities | Estimated Fair Value | Fair Value Measured on a Recurring Basis	'	'	'	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'	'	'	'
Investment securities available-for-sale	365	'	365	'	415
Estimated Fair Value	'	'	'	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'	'	'	'
Investment securities available-for-sale	1,506,996	'	1,506,996	'	1,947,706
Mortgage servicing rights	25,812	'	25,812	'	25,698
Estimated Fair Value | Quoted Prices in Active Markets for Identical Assets (Level 1)	'	'	'	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'	'	'	'
Investment securities available-for-sale	0	'	0	'	0
Mortgage servicing rights	0	'	0	'	0
Estimated Fair Value | Significant Other Observable Inputs (Level 2)	'	'	'	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'	'	'	'
Investment securities available-for-sale	1,506,996	'	1,506,996	'	1,947,706
Mortgage servicing rights	25,812	'	25,812	'	25,698
Estimated Fair Value | Significant Unobservable Inputs (Level 3)	'	'	'	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'	'	'	'
Investment securities available-for-sale	0	'	0	'	0
Mortgage servicing rights	0	'	0	'	0
Estimated Fair Value | Significant Unobservable Inputs (Level 3) | Fair Value Measured on a Non-recurring Basis	'	'	'	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'	'	'	'
Impaired loans	46,505	'	46,505	'	57,302
Carrying Amount	'	'	'	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'	'	'	'
Investment securities available-for-sale	1,506,996	'	1,506,996	'	1,947,706
Mortgage servicing rights	13,443	'	13,443	'	13,546
Carrying Amount | Significant Unobservable Inputs (Level 3) | Fair Value Measured on a Non-recurring Basis	'	'	'	'	'
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]	'	'	'	'	'
Impaired loans	63,149	'	63,149	'	80,526
Long-lived assets to be disposed of by sale	$1,785	'	$1,785	'	$1,785

Schedule_of_Estimated_Fair_Val

Schedule of Estimated Fair Values of Financial Instruments by Level of Valuation Inputs (Details) (USD $)	Jun. 30, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Financial assets:	'	'
Investment securities held-to-maturity	$592,682	$205,926
Carrying Amount	'	'
Financial assets:	'	'
Cash and cash equivalents	503,648	534,827
Investment securities available-for-sale	1,506,996	1,947,706
Investment securities held-to-maturity	586,989	203,837
Accrued interest receivable	26,497	26,450
Mortgage servicing rights	13,443	13,546
Net loans	4,428,096	4,259,514
Total financial assets	7,065,669	6,985,880
Financial liabilities:	'	'
Total deposits, excluding time deposits	5,043,387	4,943,033
Time deposits	1,135,655	1,190,717
Securities sold under repurchase agreements	462,985	457,437
Other borrowed funds	20	3
Accrued interest payable	5,316	4,963
Long-term debt	36,893	36,917
Subordinated debentures held by subsidiary trusts	82,477	82,477
Total financial liabilities	6,766,733	6,715,547
Estimated Fair Value	'	'
Financial assets:	'	'
Cash and cash equivalents	503,648	534,827
Investment securities available-for-sale	1,506,996	1,947,706
Investment securities held-to-maturity	592,682	205,926
Accrued interest receivable	26,497	26,450
Mortgage servicing rights	25,812	25,698
Net loans	4,389,772	4,246,539
Total financial assets	7,045,407	6,987,146
Financial liabilities:	'	'
Total deposits, excluding time deposits	5,043,387	4,943,033
Time deposits	1,141,585	1,196,250
Securities sold under repurchase agreements	462,985	457,437
Other borrowed funds	20	3
Accrued interest payable	5,316	4,963
Long-term debt	35,381	34,508
Subordinated debentures held by subsidiary trusts	75,200	72,045
Total financial liabilities	6,763,874	6,708,239
Quoted Prices in Active Markets for Identical Assets (Level 1) | Estimated Fair Value	'	'
Financial assets:	'	'
Cash and cash equivalents	0	0
Investment securities available-for-sale	0	0
Investment securities held-to-maturity	0	0
Accrued interest receivable	0	0
Mortgage servicing rights	0	0
Net loans	0	0
Total financial assets	0	0
Financial liabilities:	'	'
Total deposits, excluding time deposits	0	0
Time deposits	0	0
Securities sold under repurchase agreements	0	0
Other borrowed funds	0	0
Accrued interest payable	0	0
Long-term debt	0	0
Subordinated debentures held by subsidiary trusts	0	0
Total financial liabilities	0	0
Significant Other Observable Inputs (Level 2) | Estimated Fair Value	'	'
Financial assets:	'	'
Cash and cash equivalents	503,648	534,827
Investment securities available-for-sale	1,506,996	1,947,706
Investment securities held-to-maturity	592,682	205,926
Accrued interest receivable	26,497	26,450
Mortgage servicing rights	25,812	25,698
Net loans	4,343,267	4,189,237
Total financial assets	6,998,902	6,929,844
Financial liabilities:	'	'
Total deposits, excluding time deposits	5,043,387	4,943,033
Time deposits	1,141,585	1,196,250
Securities sold under repurchase agreements	462,985	457,437
Other borrowed funds	20	3
Accrued interest payable	5,316	4,963
Long-term debt	35,381	34,508
Subordinated debentures held by subsidiary trusts	75,200	72,045
Total financial liabilities	6,763,874	6,708,239
Significant Unobservable Inputs (Level 3) | Estimated Fair Value	'	'
Financial assets:	'	'
Cash and cash equivalents	0	0
Investment securities available-for-sale	0	0
Investment securities held-to-maturity	0	0
Accrued interest receivable	0	0
Mortgage servicing rights	0	0
Net loans	46,505	57,302
Total financial assets	46,505	57,302
Financial liabilities:	'	'
Total deposits, excluding time deposits	0	0
Time deposits	0	0
Securities sold under repurchase agreements	0	0
Other borrowed funds	0	0
Accrued interest payable	0	0
Long-term debt	0	0
Subordinated debentures held by subsidiary trusts	0	0
Total financial liabilities	$0	$0

Acquisitions_Details

Acquisitions (Details) (USD $)	Jun. 30, 2014	Dec. 31, 2013	Jun. 30, 2014	Feb. 10, 2014
In Thousands, except Share data, unless otherwise specified			Mountain West [Member]	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	'	'	'	$7.13

Related_Party_Transactions_Det

Related Party Transactions (Details) (USD $)	0 Months Ended	6 Months Ended	0 Months Ended
	2-May-14	Jun. 30, 2014	2-May-14
		Class A Common Stock	Class A Common Stock
			Director [Member]
Related Party Transaction [Line Items]	'	'	'
Stock Repurchased and Retired During Period, Shares	'	325,418	20,000
Stock Repurchased During Period, Value	$24.77	'	'

Recent_Authoritative_Accountin1

Recent Authoritative Accounting Guidance (Details) (USD $)	3 Months Ended	6 Months Ended
In Thousands, unless otherwise specified	Jun. 30, 2014	Jun. 30, 2014
New Accounting Pronouncements or Change in Accounting Principle [Line Items]	'	'
Number of Investments in Other Assets, Noncurrent	2	2
Accounting Standards Update 2014-01 [Member] | Investment in Affordable Housing Projects [Member]	'	'
New Accounting Pronouncements or Change in Accounting Principle [Line Items]	'	'
Other Commitment, Due in Next Twelve Months	$260	$260
Other Commitment, Due in Second Year	5,604	5,604
Other Commitment, Due in Third Year	32	32
Other Commitment, Due in Fourth Year	32	32
Other Commitment, Due in Fifth Year	32	32
Other Commitment, Due Sixth Year	32	32
Other Commitment, Due Seventh Year	32	32
Other Commitment, Due Eighth Year	32	32
Other Commitment, Due Ninth Year	21	21
Other Commitment, Due Tenth Year	21	21
Accounting Standards Update 2014-01 [Member] | Investment in Affordable Housing Projects [Member]	'	'
New Accounting Pronouncements or Change in Accounting Principle [Line Items]	'	'
Other Assets	4,656	4,656
Current Income Tax Expense (Benefit)	$7	$14

Subsequent_Events_Details

Subsequent Events (Details) (Subsequent Event [Member], USD $)	0 Months Ended
In Thousands, except Share data, unless otherwise specified	Jul. 31, 2014	Jul. 24, 2014
Subsequent Event [Line Items]	'	'
Payments to Acquire Businesses, Gross	38,479	'
Class A Common Stock	'	'
Subsequent Event [Line Items]	'	'
Dividends Payable, Amount Per Share	'	$0.16
Business Acquisition, Equity Interest Issued or Issuable, Number of Shares	1,378,230	'