Columbia Banking System (COLB) 10-K 2 Mar 15 2014 FY Annual report Financial data

Document_and_Entity_Informatio

Document and Entity Information (USD $)	12 Months Ended
	Dec. 31, 2014	Jan. 31, 2015	Jun. 30, 2014
Document Information [Line Items]
Document Type	10-K
Amendment Flag	FALSE
Document Period End Date	31-Dec-14
Document Fiscal Year Focus	2014
Document Fiscal Period Focus	FY
Entity Registrant Name	COLUMBIA BANKING SYSTEM INC
Entity Central Index Key	887343
Current Fiscal Year End Date	-19
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		57,452,815
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Public Float			$1,367,918,597

Consolidated_Balance_Sheets

Consolidated Balance Sheets (USD $)	Dec. 31, 2014		Dec. 31, 2013
In Thousands, unless otherwise specified
ASSETS
Cash and due from banks	$171,221		$165,030
Interest-earning deposits with banks	16,949		14,531
Total cash and cash equivalents	188,170		179,561
Securities available for sale at fair value (amortized cost of $2,087,069 and $1,680,491, respectively)	2,098,257		1,664,111
Federal Home Loan Bank stock at cost	33,365		32,529
Loans held for sale	1,116		735
Total loans, net of unearned income of ($59,374) and ($68,282), respectively	5,445,378	[1]	4,517,296	[1]
Loans and Leases Receivable, Allowance	69,569		72,454
Loans, net	5,375,809		4,444,842
FDIC Indemnification Asset	15,174		39,846
Interest receivable	27,802		22,206
Premises and equipment, net	172,090		154,732
Other real estate owned	22,190		35,927
Goodwill	382,537		343,952
Core deposit intangible, net	30,459		25,852
Other assets	231,877		217,289
Total Assets	8,578,846		7,161,582
LIABILITIES AND SHAREHOLDERS' EQUITY
Noninterest-bearing	2,651,373		2,171,703
Interest-bearing	4,273,349		3,787,772
Total deposits	6,924,722		5,959,475
Federal Home Loan Bank advances	216,568		36,606
Securities sold under agreements to repurchase	105,080		25,000
Other borrowings	8,248		0
Other liabilities	96,053		87,252
Total liabilities	7,350,671		6,108,333
Commitments and contingent liabilities
Preferred Stock, Shares Authorized	2,000		2,000
Preferred Stock, Shares Issued	9		9
Preferred Stock, Value, Issued	2,217		2,217
Shareholders' equity:
Authorized shares	63,033		63,033
Common Stock Shares Issued And Outstanding	57,437		51,265
Common Stock (no par value)	985,839		860,562
Retained earnings	234,498		202,514
Accumulated Other Comprehensive Income (Loss), Net of Tax	5,621		-12,044
Total shareholders' equity	1,228,175		1,053,249
Total Liabilities and Shareholders' Equity	$8,578,846		$7,161,582
[1]	(1) Reclassified to conform to the current period’s presentation. The reclassification was limited to removing the separate line items for covered loans and including the prior period balances in the line items for loans, net of unearned income and allowance for loan and lease losses.

Consolidated_Balance_Sheets_Pa

Consolidated Balance Sheets (Parenthetical) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Securities available-for-sale, amortized cost	$2,087,069	$1,680,491
Unearned income on loans	($59,374)	($68,282)
Common stock, par value	$0	$0
Common stock, shares authorized	63,033	63,033
Common stock, outstanding	57,437	51,265

Consolidated_Statements_of_Inc

Consolidated Statements of Income (USD $)	12 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Interest Income
Loans	$268,279		$266,284		$219,433
Taxable securities	28,754		20,459		18,276
Tax-exempt securities	10,830		9,837		9,941
Interest-earning deposits	179		355		854
Total interest income	308,042		296,935		248,504
Interest Expense
Deposits	3,005		3,962		5,887
Federal Home Loan Bank and Federal Reserve Bank borrowings	396		-404		2,608
Prepayment charge on Federal Home Loan Bank advances	0		1,548		603
Other borrowings	593		734		479
Total interest expense	3,994		5,840		9,577
Net Interest Income	304,048		291,095		238,927
Provision (recapture) for loan and lease losses	6,727		-101		39,367
Net interest income after provision (recapture) for loan and lease losses	297,321		291,196		199,560
Noninterest Income (Loss)
Service charges and other fees	55,555		48,351		29,998
Merchant services fees	7,975		8,812		8,154
Gain on sale of investment securities, net	552		462		3,733
Bank owned life insurance	3,823		3,570		2,861
Change in FDIC loss sharing asset	-19,989		-45,017		-24,467
Other	11,834		10,522		6,779
Total noninterest income (loss)	59,750		26,700		27,058
Noninterest Expense
Compensation and employee benefits	130,864		125,432		85,434
Occupancy	32,300		33,054		20,031
Merchant processing	4,006		3,551		3,612
Advertising and promotion	3,964		4,090		3,650
Data processing	15,369		14,076		9,714
Legal and professional fees	11,389		12,338		8,915
Taxes, licenses and fees	4,552		5,033		4,736
Regulatory premiums	4,549		4,706		3,384
Net cost (benefit) of operation of other real estate owned	-1,045		-7,401		-1,969
Amortization of intangibles	6,293		6,045		4,445
Other	27,045	[1]	29,962	[1]	20,961	[1]
Total noninterest expense	239,286		230,886		162,913
Income before income taxes	117,785		87,010		63,705
Income tax expense (benefit)	36,211		26,994		17,562
Net Income (Loss)	$81,574		$60,016		$46,143
Per Common Share
Earnings (loss) basic (dollars per share)	$1.53		$1.24		$1.16
Earnings (loss) diluted (dollars per share)	$1.52		$1.21		$1.16
Common Stock, Dividends, Per Share, Cash Paid	$0.94		$0.41		$0.98
Weighted average number of common shares outstanding	52,618		47,993		39,260
Weighted average number of diluted common shares outstanding	53,183		49,051		39,263
[1]	(1) Reclassified to conform to the current period’s presentation. The reclassification was limited to removing the separate line item for FDIC clawback liability expense within noninterest expense and including the prior period activity in the line item for other noninterest expense as well as removing the separate line item for provision for losses on covered loans and including the prior period activity in the line item for provision for loan and lease losses.

Consolidated_Statements_of_Com

Consolidated Statements of Comprehensive Income (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Net income (loss)	$81,574	$60,016	$46,143
Unrealized gain from securities:
Net unrealized holding gain (loss) from available for sale securities arising during the period, net of tax of ($10,200), $17,498 and $1,902	17,922	-30,727	-2,609
Reclassification adjustment of net gain from sale of available for sale securities included in income, net of tax of $200, $163 and $1,316	-352	-299	-2,417
Net unrealized gain from securities, net of reclassification adjustment	17,570	-31,026	-5,026
Pension plan liability adjustment:
Unrecognized net actuarial gain (loss) during the period, net of tax of $0, $780 and $0	0	-1,432	0
Less: amortization of unrecognized net actuarial loss included in net periodic pension cost, net of tax of ($54), ($135) and ($38)	95	265	42
Pension plan liability adjustment, net	95	-1,167	42
Other comprehensive income	17,665	-32,193	-4,984
Comprehensive income	$99,239	$27,823	$41,159

Consolidated_Statements_of_Com1

Consolidated Statements of Comprehensive Income (Parenthetical) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Net unrealized holding gain from available for sale securities arising during the period, tax	$10,200	($17,498)	($1,902)
Reclassification adjustment of net gain from sale of available for sale securities included in income, tax	200	163	1,316
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Net Unamortized Gain (Loss) Arising During Period, Tax	0	780	0
Less: amortization of unrecognized net actuarial loss included in net periodic pension cost, tax	($54)	($135)	($38)

Consolidated_Statements_of_Cha

Consolidated Statements of Changes in Shareholders' Equity (USD $)	Total	Preferred Stock [Member]	Common Stock [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income [Member]
In Thousands, except Share data
Balance, value at Dec. 31, 2011	$759,338	$0	$579,136	$155,069	$25,133
Balance (in shares) at Dec. 31, 2011		0	39,506,000
Net income (loss)	46,143			46,143
Other comprehensive income	-4,984				-4,984
Issuance of common stock - stock option and other plans, shares			40,000
Issuance of common stock - stock option and other plans, value	713		713
Issuance of common stock - restricted stock awards, net of canceled awards, shares			140,000
Issuance of common stock - restricted stock awards, net of canceled awards, value	1,622		1,622
Cash dividends paid on common stock	-38,824			-38,824
Preferred Stock, Dividends, Per Share, Cash Paid	$0
Common Stock, Dividends, Per Share, Cash Paid	$0.98
Balance, value at Dec. 31, 2012	764,008	0	581,471	162,388	20,149
Balance (in shares) at Dec. 31, 2012		0	39,686,000
Net income (loss)	60,016			60,016
Other comprehensive income	-32,193				-32,193
Issuance of common stock, net of offering costs, shares		9,000	11,380,000
Issuance of common stock, net of offering costs, value	276,181	2,217	273,964
Stock Adjustment Value Deferred Compensation	517
Issuance of common stock - stock option and other plans, shares			73,000
Issuance of common stock - stock option and other plans, value	1,243		1,243
Issuance of common stock - restricted stock awards, net of canceled awards, shares			144,000
Issuance of common stock - restricted stock awards, net of canceled awards, value	2,693		2,693
Tax benefit deficiency associated with share-based compensation	1,103		1,103
Purchase and retirement of common stock (in shares)			-18,000
Purchase and retirement of common stock, value	-429		-429
Dividends, Preferred Stock, Cash	-32
Cash dividends paid on common stock	-19,858			-19,858
Preferred Stock, Dividends, Per Share, Cash Paid	$0.31
Common Stock, Dividends, Per Share, Cash Paid	$0.41
Balance, value at Dec. 31, 2013	1,053,249	2,217	860,562	202,514	-12,044
Balance (in shares) at Dec. 31, 2013		9,000	51,265,000
Net income (loss)	81,574			81,574
Other comprehensive income	17,665				17,665
Issuance of common stock, net of offering costs, shares		0	4,208,000
Issuance of common stock, net of offering costs, value	116,907	0	116,907
Stock Issued During Period, Shares, Conversion of Warrants			1,722,000
Stock Issued During Period, Value, Conversion of Warrants	5,000		5,000
Stock Adjustment Value Deferred Compensation	-1
Issuance of common stock - stock option and other plans, shares	9,116		41,000
Issuance of common stock - stock option and other plans, value	929		929
Issuance of common stock - restricted stock awards, net of canceled awards, shares			225,000
Issuance of common stock - restricted stock awards, net of canceled awards, value	2,859		2,859
Tax benefit deficiency associated with share-based compensation	205		205
Purchase and retirement of common stock (in shares)			-24,000
Purchase and retirement of common stock, value	-622		-622
Dividends, Preferred Stock, Cash	-96
Cash dividends paid on common stock	-49,494			-49,494
Preferred Stock, Dividends, Per Share, Cash Paid	$0.94
Common Stock, Dividends, Per Share, Cash Paid	$0.94
Balance, value at Dec. 31, 2014	$1,228,175	$2,217	$985,839	$234,498	$5,621
Balance (in shares) at Dec. 31, 2014		9,000	57,437,000

Consolidated_Statements_of_Cas

Consolidated Statements of Cash Flows (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Cash Flows From Operating Activities
Net Income (Loss)	$81,574		$60,016		$46,143
Adjustments to reconcile net income to net cash provided by operating activities:
Provision (recapture) for loan and lease losses	6,727		-101		39,367
Stock-based compensation expense	2,859		2,844		1,622
Depreciation, amortization and accretion	44,459		40,431		57,305
Net realized gain on sale of securities	-552		-462		-3,733
Net realized (gain) loss on sale of other assets	564		-48		-456
Net realized (gain) loss on sale of other real estate owned	-5,909		-10,539		-11,634
Disposal Group, Not Discontinued Operation, Gain (Loss) on Disposal	-565		0		0
Write-down on other real estate owned	4,039		2,035		8,300
Deferred income tax expense (benefit)	14,646		5,413		-3,656
Net change in:
Loans held for sale	229		1,828		-415
Interest receivable	-944		-7,938		1,019
Interest payable	89		-122		-629
Other assets	-4,479		-3,385		-2,113
Other liabilities	-5,119		-10,336		3,779
Net cash provided by operating activities	137,618		79,636		134,899
Cash Flows From Investing Activities
Payments for (Proceeds from) Loans and Leases	-440,376		-161,827		-92,088
Purchases of securities available for sale	-363,693		-457,985		-322,342
Purchases of premises and equipment	-12,485		-13,133		-17,137
Proceeds from FDIC reimbursement on loss-sharing asset	5,950		9,246		54,649
Proceeds from sales of securities available for sale	63,292		166,881		95,165
Proceeds from principal repayments and maturities of securities available for sale	180,648		293,940		236,749
Proceeds from sales of loans held for investment and other assets	4,128		4,031		4,414
Proceeds from sales of other real estate and other personal property owned	28,559	[1]	36,453	[1]	49,004	[1]
Payment to FDIC Related to Loss-Sharing Asset	-3,451		0		0
Capital improvements on other real estate properties	0		-3,577		-11
Payments to Acquire Intangible Assets	0		-919		0
Disposal Group, Not Discontinued Operation, Cash paid in disposal of assets	-16,788		0		0
Net cash acquired in business combinations	32,255		-154,170		0
Net cash (used in) provided by investing activities	-521,961		-281,060		8,403
Cash Flows From Financing Activities
Net increase (decrease) in deposits	250,629		33,983		226,556
Increase (Decrease) in Federal Funds Purchased and Securities Sold under Agreements to Repurchase, Net	21,037		0		0
Proceeds from exercise of stock options	929		1,092		713
Proceeds from Warrant Exercises	5,000		0		0
Proceeds from Federal Home Loan Bank advances	1,602,000		1,215,100		100
Proceeds from Federal Reserve Bank borrowings	800		50		100
Repayment of Federal Home Loan Bank advances	-1,422,000		-1,313,000		-112,210
Repayment of Federal Reserve Bank borrowings	-800		-50		-100
Payment of preferred stock dividends	-96		-32		0
Payment of common stock dividends	-49,494		-19,858		-38,824
Repayments of Other Debt	-14,636	[1]	-51,000	[1]	0	[1]
Payment for purchase and retirement of common stock	-622		-429		0
Proceeds from excess tax benefit from stock-based compensation	205		1,203		0
Net cash used in financing activities	392,952		-132,941		76,335
Increase (decrease) in cash and cash equivalents	8,609		-334,365		219,637
Cash and cash equivalents at beginning of period	179,561		513,926		294,289
Cash and cash equivalents at end of period	188,170		179,561		513,926
Supplemental Information:
Cash paid for interest	3,904		5,962		10,206
Cash paid for income tax	21,230		26,754		11,927
Non-cash investing activities
Loans transferred to other real estate owned	10,200		18,100		21,627
Stock Issued	$116,907		$276,181		$0
[1]	Reclassified to conform to the current period’s presentation. The reclassification was limited to removing the separate line item for sales of covered other real estate owned and including the prior period activity in the line item for sales of other real estate and other personal property owned as well as removing the separate line item for repayment of long-term subordinated debt and including prior period activity in the line item for repayment of other borrowings.

Summary_of_Significant_Account

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2014
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Summary of Significant Accounting Policies
	Organization
	Columbia Banking System, Inc. (the “Corporation”, “we”, “our”, “Columbia” or the “Company”) is the holding company for Columbia State Bank (“Columbia Bank” or the “Bank”) and West Coast Trust Company, Inc. (“West Coast Trust”). The Bank provides a full range of financial services through 154 branch locations, including 78 in the State of Washington, 60 in Oregon and 16 in Idaho. West Coast Trust provides fiduciary, agency, trust and related services, and life insurance products. Because the Bank comprises substantially all of the business of the Corporation, references to the “Company” mean the Corporation and the Bank together. The Corporation is approved as a bank holding company pursuant to the Gramm-Leach-Bliley Act of 1999.
	The Company’s accounting and reporting policies conform to accounting principles generally accepted in the United States of America (“GAAP”) and practices in the financial services industry. To prepare the financial statements in conformity with GAAP, management must make estimates and assumptions that affect the reported amounts of assets and liabilities at the date of the financial statements, and income and expenses during the reporting period. Circumstances and events that differ significantly from those underlying our estimates and assumptions could cause actual financial results to differ from our estimates. The most significant estimates included in the financial statements relate to the allowance for loan and lease losses, business combinations, purchased credit impaired loans, Federal Deposit Insurance Corporation (“FDIC”) loss sharing asset and goodwill impairment.
	The Company has applied its accounting policies and estimation methods consistently in all periods presented in these financial statements (to the periods in which they applied), except for the adoption of Accounting Standards Update (“ASU”) 2012-06 Subsequent Accounting for an Indemnification Asset Recognized at the Acquisition Date as a Result of a Government-Assisted Acquisition of a Financial Institution on January 1, 2013. As a result of adoption of the ASU, the Company adjusted the indemnification asset amortization period to be the term of the FDIC loss-sharing agreement if it was shorter than the term of the acquired loans.
	Correction of Immaterial Error Related to Prior Periods
	During the year ended December 31, 2014, the Company made a $2.6 million adjustment which increased interest income on taxable securities as a result of identifying that the premium amortization related to the Company’s mortgage-backed securities, as calculated by a third-party provider, was not being amortized utilizing an acceptable method under accounting principles generally accepted in the United States. The adjustment reflects the one-time correction necessary to change the accounting for premium amortization to be in conformity with the interest method. Based upon an evaluation of all relevant factors, management believes the correcting adjustment did not have a material impact on the Company’s current or previously reported results.
	Consolidation
	The consolidated financial statements of the Company include the accounts of the Corporation and its subsidiaries, including the Bank and West Coast Trust. Intercompany balances and transactions have been eliminated in consolidation.
	Cash and cash equivalents
	Cash and cash equivalents include cash and due from banks, and interest bearing balances due from correspondent banks and the Federal Reserve Bank. Cash and cash equivalents have a maturity of 90 days or less at the time of purchase.
	Securities
	Securities are classified based on management’s intention on the date of purchase. All securities are classified as available for sale and are presented at fair value. Unrealized gains or losses on securities available for sale are excluded from net income but are included as separate components of other comprehensive income, net of taxes. Purchase premiums or discounts on securities available for sale are amortized or accreted into income using the interest method over the terms of the individual securities. The Company performs a quarterly assessment to determine whether a decline in fair value below amortized cost is other-than-temporary. Amortized cost includes adjustments made to the cost of an investment for accretion, amortization, collection of cash and previous other-than temporary impairment recognized in earnings. Other-than-temporary impairment exists when it is probable that the Company will be unable to recover the entire amortized cost basis of the security.
	In performing the quarterly assessment for debt securities, management considers whether or not the Company expects to recover the entire amortized cost basis of the security. In addition, management also considers whether it is more likely than not that it will not have to sell the security before recovery of its cost basis. If the Company intends to sell a security or it is more likely than not it will be required to sell a security prior to recovery of its cost basis, the entire amount of impairment is recognized in earnings. If the Company does not intend to sell the security or it is not more likely than not it will be required to sell the security prior to recovery of its cost basis, the credit loss component of impairment is recognized in earnings and impairment associated with non-credit factors, such as market liquidity, is recognized in other comprehensive income net of tax. A credit loss is the difference between the cost basis of the security and the present value of cash flows expected to be collected, discounted at the security’s effective interest rate at the date of acquisition. The cost basis of an other-than-temporarily impaired security is written down by the amount of impairment recognized in earnings. The new cost basis is not adjusted for subsequent recoveries in fair value. However, the difference between the new amortized cost basis and the cash flows expected to be collected is accreted as interest income. The total other-than-temporary impairment, if any, is presented in the consolidated statements of income with a reduction for the amount of other-than-temporary impairment that is recognized in other comprehensive income, if any.
	Realized gains or losses on sales of securities available for sale are recorded using the specific identification method.
	Federal Home Loan Bank Stock
	The Company’s investment in Federal Home Loan Bank (“FHLB”) stock is carried at par value because the shares can only be redeemed with the FHLB at par. The Company is required to maintain a minimum level of investment in FHLB stock based on specific percentages of its outstanding mortgages and FHLB advances. Stock redemptions are at the discretion of the FHLB or of the Company, upon five years’ prior notice for FHLB Class B stock or six months notice for FHLB Class A stock to the FHLB. FHLB stock is subject to recoverability testing per the Financial Services—Depository and Lending topic of the FASB Accounting Standards Codification (“ASC”).
	Loans
	Loans, excluding purchased credit impaired loans are generally carried at the unpaid principal balance, net of premiums, unearned discounts and net deferred loan fees. Net deferred loan fees include deferred unamortized fees less direct incremental loan origination costs. Net deferred loan fees, premiums and unearned discounts are amortized into interest income using either the interest method or straight-line method over the terms of the loans, adjusted for actual prepayments. The amortization is calculated using the interest method for all loans except revolving loans, for which the straight-line method is used. Interest income is accrued as earned. Fees related to lending activities other than the origination or purchase of loans are recognized as noninterest income during the period the related services are performed.
	Nonaccrual loans—Loans are placed on nonaccrual status when a loan becomes contractually past due 90 days with respect to interest or principal unless the loan is both well secured and in the process of collection, or if full collection of interest or principal becomes uncertain. When a loan is placed on nonaccrual status, any accrued and unpaid interest receivable is reversed and the recognition of net deferred loan fees, premiums and unearned discounts ceases. Thereafter, interest collected on the loan is accounted for on the cash collection or cost recovery method until qualifying for return to accrual status. Generally, a loan may be returned to accrual status when the delinquent principal and interest are brought current in accordance with the terms of the loan agreement for a minimum period of six months and future payments are reasonably assured.
	Impaired loans—Loans are considered impaired when based on current information and events, it is probable that the Company will be unable to collect all amounts due according to the contractual terms of the loan agreement or when a loan has been modified in a troubled debt restructuring. The assessment for impairment occurs when and while such loans are designated as classified per the Company’s internal risk rating system or when and while such loans are on nonaccrual. All nonaccrual loans greater than $500,000 and all troubled debt restructured loans are considered impaired and analyzed individually on a quarterly basis. Classified loans with an outstanding balance greater than $500,000 are evaluated for potential impairment on a quarterly basis.
	When a loan with unique risk characteristics has been identified as being impaired, the amount of impairment will be measured by the Company using discounted cash flows, except when it is determined that the remaining source of repayment for the loan is the operation or liquidation of the underlying collateral. In these cases, the current fair value of the collateral, reduced by costs to sell, will be used in place of discounted cash flows. As a final alternative, the observable market price of the debt may be used to assess impairment. Predominantly, the Company uses the fair value of collateral approach based upon a reliable valuation.
	When the measurement of the impaired loan is less than the recorded amount of the loan, an impairment is recognized by recording a charge-off to the allowance for loan and lease losses or by designating a specific reserve. The Company’s policy is to record cash receipts received on impaired loans first as reductions to principal and then to interest income.
	Restructured Loans—A loan is classified as a troubled debt restructuring when a borrower is experiencing financial difficulties that lead to a restructuring of the loan, and the Company grants concessions to the borrower in the restructuring that it would not otherwise consider. These concessions may include interest rate reductions, principal forgiveness, extension of maturity date and other actions intended to minimize potential losses. Generally, a nonaccrual loan that is restructured remains on nonaccrual status for a period of six months to demonstrate that the borrower can meet the restructured terms. If the borrower’s performance under the new terms is not reasonably assured, the loan remains classified as a nonaccrual loan.
	Purchased Credit Impaired Loans (“PCI Loans”)—Loans acquired with evidence of credit deterioration since origination for which it is probable that all contractually required payments will not be collected are accounted for under ASC 310-30, Loans and Debt Securities Acquired with Deteriorated Credit Quality, formerly SOP 03-3 Accounting for Certain Loans or Debt Securities Acquired in a Transfer. In addition, because of the significant discounts associated with certain of the acquired loan portfolios, the Company elected to account for those certain acquired loans under ASC 310-30.
	In situations where such loans have similar risk characteristics, loans are aggregated into pools to estimate cash flows. A pool is accounted for as a single asset with a single interest rate, cumulative loss rate and cash flow expectation. Expected cash flows at the acquisition date in excess of the fair value of loans are considered to be accretable yield, which is recognized as interest income over the life of the loan pool using a level yield method if the timing and amount of the future cash flows of the pool is reasonably estimable. Subsequent to the acquisition date, any increases in cash flow over those expected at purchase date in excess of fair value are recorded as interest income prospectively. Any subsequent decreases in cash flow over those expected at purchase date due to credit deterioration are recognized by recording an allowance for losses on purchased credit impaired loans. Any disposals of loans, including sales of loans, payments in full or foreclosures result in the removal of the loan from the loan pool at the carrying amount.
	Unfunded loan commitments—Unfunded commitments are generally related to providing credit facilities to clients of the Bank and are not actively traded financial instruments. These unfunded commitments are disclosed as financial instruments with off-balance sheet risk in Note 17 in the Notes to Consolidated Financial Statements.
	Allowance for Loan and Lease Losses
	The Company accounts for the credit risk associated with lending activities through its allowance for loan and lease losses and provision for loan and lease losses. The provision is the expense recognized in the consolidated statements of income to adjust the allowance to the levels deemed appropriate by management, as determined through application of the Company’s allowance methodology procedures. The provision for loan and lease losses reflects management’s judgment of the adequacy of the allowance for loan and lease losses. Loan and lease losses are charged against the allowance when management believes the collectability of a loan balance is unlikely. Subsequent recoveries, if any, are credited to the allowance.
	The allowance for loan and lease losses is evaluated on a regular basis by management and is based upon management’s periodic review of the collectability of the loans in light of historical experience, the nature and volume of the loan portfolio, adverse situations that may affect the borrower’s ability to repay, and estimated value of any underlying collateral and prevailing economic conditions. This evaluation is inherently subjective as it requires estimates that are susceptible to significant revision as more information becomes available.
	The allowance consists of general, specific, and unallocated components. The general component covers loans not specifically measured for impairment and is based on historical loss experience adjusted for qualitative factors. The specific component relates to loans that are impaired. For impaired loans an allowance is established when the discounted cash flows (or collateral value or observable market price) of the impaired loan is lower than the carrying value of that loan. The unallocated allowance provides for other credit losses inherent in the Company’s loan portfolio that may not have been contemplated in the general and specific components of the allowance. This unallocated amount generally comprises less than 5% of the allowance. The unallocated amount is reviewed periodically based on trends in credit losses, the results of credit reviews and overall economic trends.
	Allowance for Loan Losses on Purchased Credit Impaired Loans
	The Company updates its cash flow projections for purchased credit impaired loans accounted for under ASC 310-30 on a quarterly basis. Assumptions utilized in this process include projections related to probability of default, loss severity, prepayment and recovery lag. Projections related to probability of default and prepayment are calculated utilizing a loan migration analysis. The loan migration analysis is a matrix of probability that is used to estimate the probability of a loan pool transitioning into a particular delinquency state given its delinquency state at the remeasurement date. Loss severity factors are based upon either actual charge-off data within the loan pools or industry averages and recovery lags are based upon the collateral within the loan pools.
	Any decreases in expected cash flows after the acquisition date and subsequent measurement periods are recognized by recording a provision for loan losses. See Purchased Credit Impaired Loans for further discussion.
	Allowance for Unfunded Commitments and Letters of Credit
	The allowance for unfunded commitments is maintained at a level believed by management to be sufficient to absorb estimated probable losses related to these unfunded credit facilities. The determination of the adequacy of the allowance is based on periodic evaluations of the unfunded credit facilities including an assessment of the probability of commitment usage, credit risk factors for loans outstanding to these same customers, and the terms and expiration dates of the unfunded credit facilities. The allowance for unfunded commitments is included in other liabilities on the consolidated balance sheets, with changes to the balance charged against noninterest expense.
	Premises and Equipment
	Land, buildings, leasehold improvements and equipment are stated at cost less accumulated depreciation and amortization. Gains or losses on dispositions are reflected in current operations. Expenditures for improvements and major renewals are capitalized, and ordinary maintenance, repairs and small purchases are charged to operating expenses. Depreciation and amortization are computed based on the straight-line method over the estimated useful lives of the various classes of assets. The ranges of useful lives for the principal classes of assets are as follows:
	Buildings and building improvements	5 to 39 years
	Leasehold improvements	Term of lease or useful life, whichever is shorter
	Furniture, fixtures and equipment	3 to 7 years
	Vehicles	5 years
	Computer software	3 to 5 years
	Software
	Capitalized software is stated at cost, less accumulated amortization. Amortization is computed on a straight-line basis and charged to expense over the estimated useful life of the software which is generally three years. Capitalized software is included in Premises and equipment, net in the consolidated balance sheets.
	Other Real Estate Owned
	OREO is composed of real estate acquired in satisfaction of loans. Properties acquired by foreclosure or deed in lieu of foreclosure are transferred to OREO and are recorded at fair value less estimated costs to sell, at the date of transfer of the property. If the carrying value exceeds the fair value at the time of the transfer, the difference is charged to the allowance for loan and lease losses. The fair value of the OREO property is based upon current appraisal. Losses that result from the ongoing periodic valuation of these properties are charged to the net cost of operation of OREO in the period in which they are identified. Improvements to the OREO are capitalized and holding costs are charged to the net cost of operation of OREO as incurred.
	FDIC Loss-sharing Asset
	The acquisition date fair value of the reimbursement the Company expected to receive from the FDIC under loss-sharing agreements was recorded in the FDIC loss-sharing asset on the consolidated balance sheet. Subsequent to initial recognition, the FDIC loss-sharing asset is reviewed quarterly and adjusted for any changes in expected cash flows. These adjustments are measured on the same basis as the related covered assets. Any decrease in expected cash flows for the covered assets due to an increase in expected credit losses will increase the FDIC loss-sharing asset and any increase in expected future cash flows for the covered assets due to a decrease in expected credit losses will decrease the FDIC loss-sharing asset. Changes in the estimated cash flows on covered assets that are immediately recognized in income generally result in a similar immediate adjustment to the loss-sharing asset while changes in expected cash flows on covered assets that are accounted for as an adjustment to yield generally result in adjustments to the amortization or accretion rate for the loss-sharing asset. Increases and decreases to the FDIC loss-sharing asset are recorded as adjustments to noninterest income.
	Goodwill and Intangibles
	Net assets of companies acquired in purchase transactions are recorded at fair value at the date of acquisition. Identified intangibles are amortized on an accelerated basis over the period benefited. Goodwill is not amortized but is reviewed for potential impairment during the third quarter on an annual basis or, more frequently, if events or circumstances indicate a potential impairment, at the reporting unit level. A reporting unit is an operating segment or one level below an operating segment for which discrete financial information is available and regularly reviewed by management. The Company consists of a single reporting unit. If the fair value of the reporting unit, including goodwill, is determined to be less than the carrying amount of the reporting unit, a further test is required to measure the amount of impairment. If an impairment loss exists, the carrying amount of goodwill is adjusted to a new cost basis. Subsequent reversal of a previously recognized goodwill impairment loss is prohibited.
	Intangible assets are evaluated for impairment if events and circumstances indicate a possible impairment. Such evaluation of other intangible assets is based on undiscounted cash flow projections. At December 31, 2014, intangible assets included on the consolidated balance sheets principally consists of a core deposit intangible amortized using an accelerated method with an original estimated life 10 years.
	Income Taxes
	The provision for income taxes includes current and deferred income tax expense on net income adjusted for permanent and temporary differences such as interest income on state and municipal securities and affordable housing credits. Deferred tax assets and liabilities are recognized for the expected future tax consequences of existing temporary differences between the financial reporting and tax reporting basis of assets and liabilities using enacted tax laws and rates. The effect on deferred tax assets and liabilities of a change in tax rates is recognized in income in the period that includes the enactment date. On a quarterly basis, management evaluates deferred tax assets to determine if these tax benefits are expected to be realized in future periods. This determination is based on facts and circumstances, including the Company’s current and future tax outlook. To the extent a deferred tax asset is no longer considered “more likely than not” to be realized, a valuation allowance is established.
	We recognize the tax benefit from uncertain tax positions only if it is more likely than not that the tax positions will be sustained on examination by the tax authorities, based on the technical merits of the position. The tax benefit is measured based on the largest benefit that has a greater than 50% likelihood of being realized upon ultimate settlement. We recognize interest and penalties related to unrecognized tax benefits in “Provision for income taxes” in the consolidated statements of income.
	Advertising
	Advertising costs are generally expensed as incurred.
	Earnings per Common Share
	The Company’s capital structure includes convertible preferred shares, common shares, restricted common shares, common share options, and during portions of 2014 and 2013, warrants to purchase common shares. Restricted common shares participate in dividends declared on common shares at the same rate as common shares. Preferred shares participate in dividends declared on common shares on an “as if converted” basis. Accordingly, the Company calculates earnings per common share (“EPS”) using the two-class method under the Earnings per Share topic of the FASB ASC. The two-class method is an earnings allocation formula that treats a participating security as having rights to earnings that otherwise would have been available to common shareholders but does not require the presentation of basic and diluted EPS for securities other than common shares.
	Under the two-class method, basic EPS is computed by dividing earnings allocated to common shareholders by the weighted average number of common shares outstanding for the period. Earnings allocated to common shareholders represents net income reduced by earnings allocated to participating securities. Participating securities include nonvested restricted stock awards and preferred stock. Diluted EPS is computed in the same manner as basic earnings per share except that the denominator is increased to include the number of additional common shares that would have been outstanding if certain shares issuable upon exercise of options and warrants were included unless those additional shares would have been anti-dilutive. For the diluted EPS computation, the treasury stock method is applied and compared to the two-class method and whichever method results in a more dilutive impact is utilized to calculate diluted EPS.
	Share-Based Payment
	The Company accounts for stock options and stock awards in accordance with the Compensation—Stock Compensation topic of the FASB ASC. Authoritative guidance requires the Company to measure the cost of employee services received in exchange for an award of equity instruments, such as stock options or stock awards, based on the fair value of the award on the grant date. This cost must be recognized in the consolidated statements of income over the vesting period of the award.
	The Company issues restricted stock awards which generally vest over a four- or five-year period during which time the holder receives dividends and has full voting rights. Restricted stock is valued at the closing price of the Company’s stock on the date of an award.
	Derivatives and Hedging Activities
In accordance with the Derivatives and Hedging topic of the FASB ASC, the Company recognizes derivatives as assets or liabilities on the consolidated balance sheets at their fair value. The Company periodically enters into interest rate contracts with customers and offsetting contracts with third parties. As these interest rate contracts are not designated as hedges under the Derivatives and Hedging topic of the FASB ASC, the changes in fair value of these instruments are recognized immediately in earnings.
Accounting Pronouncements
During the year ended December 31, 2014, the following Accounting Standards Updates were issued or became effective:
In August 2014, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) No. 2014-15, Disclosure of Uncertainties about an Entity’s Ability to Continue as a Going Concern. The Update provides U.S. GAAP guidance on management’s responsibility in evaluating whether there is substantial doubt about a company’s ability to continue as a going concern and about related footnote disclosures. For each reporting period, management will be required to evaluate whether there are conditions or events that raise substantial doubt about a company’s ability to continue as a going concern within one year from the date the financial statements are issued. The new standard is effective for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2016. Early adoption is permitted. The adoption of ASU No. 2014-15 is not expected to have a material impact on the Company’s consolidated financial statements.
In June 2014, the FASB issued ASU No. 2014-12, Accounting for Share-Based Payments When the Terms of an Award Provide That a Performance Target Could Be Achieved after the Requisite Services Period. The amendments in ASU 2014-12 provide guidance for determining compensation cost under specific circumstances when an employee is eligible to vest in an award regardless of whether the employee is rendering service on the date the performance target is achieved. ASU 2014-12 becomes effective for annual and interim periods beginning after December 15, 2015 with early adoption permitted. As of December 31, 2014, the Company did not have any share-based payment awards that include performance targets that could be achieved after the requisite service period. As such, the adoption of ASU No. 2014-12 is not expected to have a material impact on the Company’s consolidated financial statements.
In June 2014, the FASB issued ASU 2014-11, Repurchase-to-Maturity Transactions, Repurchase Financings, and Disclosures. The amendments in ASU 2014-11 change the accounting for repurchase-to-maturity transactions and linked repurchase financings to secured borrowing accounting, which is consistent with accounting for other repurchase agreements. Additionally, the amendment requires new disclosures on transfers accounted for as sales in transactions that are economically similar to repurchase agreements and requires increased transparency on collateral pledged in secured borrowings. The amendments in this update will be effective for the first interim or annual period beginning after December 31, 2014, with the exception of the collateral disclosures which will be effective for interim periods beginning after March 15, 2015. Early application is not permitted. The Company is currently assessing the impact that this guidance will have on its consolidated financial statements, but does not expect the guidance to have a material impact on the Company’s consolidated financial statements.
In May 2014, the FASB issued ASU No. 2014-09, Revenue from Contracts with Customers. The guidance in this update supersedes the revenue recognition requirements in ASC Topic 605, Revenue Recognition, and most industry-specific guidance throughout the industry topics of the codification. For public companies, this update will be effective for interim and annual periods beginning after December 15, 2016. The Company is currently assessing the impact that this guidance will have on its consolidated financial statements, but does not expect the guidance to have a material impact on the Company’s consolidated financial statements.
In April 2014, the the FASB issued ASU No. 2014-08, Reporting Discontinued Operations and Disclosures of Disposals of Components of an Entity. ASU 2014-08 raises the threshold for a disposal to qualify as a discontinued operation and requires new disclosures of both discontinued operations and certain other disposals that do not meet the definition of a discontinued operation. It is effective for annual periods beginning on or after December 15, 2014. Early adoption is permitted but only for disposals that have not been reported in financial statements previously issued. The Company is assessing the impact of the new guidance on its consolidated financial statements, but does not expect the guidance to have a material impact on the Company’s consolidated financial statements.
In January 2014, the FASB issued ASU 2014-04, Reclassification of Residential Real Estate Collateralized Consumer Mortgage Loans Upon Foreclosure. The update clarifies when a creditor would be considered to have received physical possession of residential real estate property collateralizing a consumer mortgage loan such that all or a portion of the loan would be derecognized and the real estate property recognized. Under the guidance, a consumer loan collateralized by residential real estate should be reclassified to other real estate owned when (1) the creditor obtains legal title to the residential property or (2) the borrower conveys all interest in the property to the creditor to satisfy the loan by completing a deed in lieu of foreclosure or similar agreement. In addition, an entity is required to disclose the amount of residential real estate meeting the conditions above, and the recorded investment in consumer mortgage loans secured by residential real estate that are in the process of foreclosure. ASU 2014-04 is effective for annual and interim reporting periods within those annual periods, beginning after December 15, 2014. Adoption of the new guidance is not expected to have a significant impact on the Company’s consolidated financial statements.
In January 2014, the FASB issued ASU No. 2014-01, Accounting for Investments in Qualified Affordable Housing Projects. The update provides guidance on accounting for investments by a reporting entity in flow-through limited liability entities that manage or invest in affordable housing projects that qualify for the low-income housing tax credit. The amendments in this update permit the reporting entity to make an accounting policy election to account for its investments in qualified affordable housing projects using the proportional amortization method if certain conditions are met. Those not electing the proportional amortization method would account for such investments using the equity method or cost method. Under the proportional amortization method, the cost of the investment is amortized each reporting period in proportion to the tax credits received. Under the new guidance, classification of the amortization would change from noninterest expense to income tax expense. ASU 2014-01 is effective for annual and interim reporting periods within those annual periods, beginning after December 15, 2014. The guidance is to be applied retrospectively to all periods presented. The Company adopted this ASU prospectively on December 31, 2014 as the retrospective adjustments were not material. The net investment balance at December 31, 2014 was $7.3 million. The amount of affordable housing tax credits recognized during 2014 was $1.5 million. Using the proportional amortization method, the amount recognized as a component of income tax expense for 2014 was $2.0 million, inclusive of the adjustment made to remove the previously recorded deferred tax asset. Prior to adopting this guidance, the Company accounted for such investments using the equity method. Under the equity method, the Company would have recognized $1.1 million as a component of other noninterest expense. Adoption of this ASU did not have a material impact on the Company's consolidated financial statements.

Business_Combinations

Business Combinations	12 Months Ended
	Dec. 31, 2014
Business Combinations [Abstract]
Business Combination Disclosure [Text Block]	Business Combinations
	Intermountain Community Bancorp
	On November 1, 2014, the Company completed its acquisition of Intermountain Community Bancorp and its wholly-owned banking subsidiary Panhandle State Bank ("Intermountain"). The Company acquired 100% of the voting equity interests of Intermountain. The primary reason for the acquisition was to expand the Company's geographic footprint into the state of Idaho, consistent with its ongoing growth strategy.
	The assets acquired and liabilities assumed have been accounted for under the acquisition method of accounting (formerly the purchase method). The assets and liabilities, both tangible and intangible, were recorded at their estimated fair values as of the November 1, 2014 acquisition date. Initial accounting for deferred taxes was incomplete as of December 31, 2014. The amount currently recognized in the financial statements has been determined provisionally as the final Intermountain Community Bancorp tax return has not yet been completed. The application of the acquisition method of accounting resulted in the recognition of goodwill of $38.6 million and a core deposit intangible of $10.9 million, or 1.75% of core deposits. The goodwill represents the excess purchase price over the estimated fair value of the net assets acquired. The goodwill is not deductible for income tax purposes.
	The table below summarizes the amounts recognized as of the acquisition date for each major class of assets acquired and liabilities assumed:
		November 1, 2014
		(in thousands)
	Purchase price as of November 1, 2014	$	131,935
	Recognized amounts of identifiable assets acquired and (liabilities assumed), at fair value:
	Cash and cash equivalents	$	47,283
	Investment securities	299,458
	Federal Home Loan Bank stock	2,124
	Acquired loans	502,595
	Interest receivable	4,656
	Premises and equipment	20,696
	Other real estate owned	2,752
	Core deposit intangible	10,900
	Other assets	35,353
	Deposits	(736,795		)
	Other borrowings	(22,904		)
	Securities sold under agreements to repurchase	(59,043		)
	Other liabilities	(13,725		)
	Total fair value of identifiable net assets	93,350
	Goodwill	$	38,585
	See Note 10, Goodwill and Other Intangible Assets, for further discussion of the accounting for goodwill and other intangible assets.
	The operating results of the Company include the operating results produced by the acquired assets and assumed liabilities for the period November 1, 2014 to December 31, 2014. Disclosure of the amount of Intermountain’s revenue and net income (excluding integration costs) included in Columbia’s consolidated income statement is impracticable due to the integration of the operations and accounting for this acquisition.
	The following table presents certain unaudited pro forma information for illustrative purposes only, for the years ended December 31, 2014 and 2013 as if Intermountain had been acquired on January 1, 2013. This unaudited estimated pro forma financial information combines the historical results of Intermountain with the Company’s consolidated historical results and includes certain adjustments reflecting the estimated impact of certain fair value adjustments for the respective periods. The pro forma information is not indicative of what would have occurred had the acquisition occurred on January 1, 2013. In particular, no adjustments have been made to eliminate the impact of other-than-temporary impairment losses and losses recognized on the sale of securities that may not have been necessary had the investment securities been recorded at fair value as of January 1, 2013. The unaudited pro forma information does not consider any changes to the provision for credit losses resulting from recording loan assets at fair value. Additionally, Columbia expects to achieve further operating cost savings and other business synergies, including revenue growth, as a result of the acquisition which are not reflected in the pro forma amounts that follow. As a result, actual amounts would have differed from the unaudited pro forma information presented.
		Unaudited Pro Forma
		Years Ended December 31,
		2014			2013
		(in thousands except per share)
	Total revenues (net interest income plus noninterest income)	$	397,152		$	360,655
	Net income	$	85,939		$	72,587
	Earnings per share - basic	$	1.56		$	1.32
	Earnings per share - diluted	$	1.55		$	1.31
	The following table shows the impact of the acquisition-related expenses related to the acquisition of Intermountain for the periods indicated to the various components of noninterest expense:
		Year ended December 31,
		2014
		(in thousands)
	Noninterest Expense
	Compensation and employee benefits	$	2,077
	Occupancy	44
	Advertising and promotion	464
	Data processing and communications	—
	Legal and professional fees	2,114
	Other	197
	Total impact of acquisition-related costs to noninterest expense	$	4,896
	West Coast Bancorp
	On April 1, 2013, the Company completed its acquisition of West Coast Bancorp (“West Coast”). The Company paid $540.8 million in total consideration to acquire 100% of the voting equity interests of West Coast. The primary reason for the acquisition was to expand the Company’s geographic footprint consistent with its ongoing growth strategy. The fair value of the net assets acquired totaled $312.4 million, including $1.88 billion of deposits, $1.41 billion of loans and $15.3 million of other intangible assets. Goodwill of $228.4 million was recorded as part of the acquisition. The goodwill is not deductible for income tax purposes.
	The operating results of the Company include the operating results produced by the acquired assets and assumed liabilities for the period April 1, 2013 to December 31, 2014. Disclosure of the amount of West Coast’s revenue and net income (excluding integration costs) included in Columbia’s consolidated income statement is impracticable due to the integration of the operations and accounting for this acquisition.
	The following table presents certain unaudited pro forma information for illustrative purposes only, for the years ended December 31, 2013 and 2012 as if West Coast had been acquired on January 1, 2012. The unaudited estimated pro forma information combines the historical results of West Coast with the Company’s consolidated historical results and includes certain adjustments reflecting the estimated impact of certain fair value adjustments for the respective periods. The pro forma information is not indicative of what would have occurred had the acquisition occurred on January 1, 2012. In particular, no adjustments have been made to eliminate the impact of other-than-temporary impairment losses and losses recognized on the sale of securities that may not have been necessary had the investment securities been recorded at fair value on January 1, 2012. The unaudited pro forma information does not consider any changes to the provision for credit losses resulting from recording loan assets at fair value. Additionally, Columbia expects to achieve further operating cost savings and other business synergies, including revenue growth, as a result of the acquisition which are not reflected in the pro forma amounts that follow. As a result, actual amounts would have differed from the unaudited pro forma information presented.
		Unaudited Pro Forma
		Years Ended December 31,
		2013			2012
		(in thousands except per share)
	Total revenues (net interest income plus noninterest income)	$	337,712		$	420,167
	Net income	$	76,496		$	91,261
	Earnings per share - basic	$	1.5		$	1.79
	Earnings per share - diluted	$	1.46		$	1.74
	The following table shows the impact of the acquisition-related expenses related to the acquisition of West Coast for the periods indicated to the various components of noninterest expense:
		Years ended December 31,
		2014			2013		2012
		(in thousands)
	Noninterest Expense
Compensation and employee benefits	$	798		$	8,440	$	—
Occupancy	696			4,684		—
Advertising and promotion	—			877		2
Data processing and communications	684			767		—
Legal and professional fees	383			4,766		1,760
Other	1,975			5,954		18
Total impact of acquisition-related costs to noninterest expense	$	4,536		$	25,488	$	1,780

Cash_and_Cash_Equivalents

Cash and Cash Equivalents	12 Months Ended
	Dec. 31, 2014
Cash and Cash Equivalents [Abstract]
Cash and Cash Equivalents	Cash and Cash Equivalents
	The Company is required to maintain an average reserve balance with the Federal Reserve Bank or maintain such reserve balance in the form of cash. The average required reserve balance for the years ended December 31, 2014 and 2013 was approximately $47.4 million and $36.3 million, respectively, and was met by holding cash and maintaining an average balance with the Federal Reserve Bank.

Securities

Securities	12 Months Ended
	Dec. 31, 2014
Available-for-sale Securities [Abstract]
Securities	Securities
	At December 31, 2014 the Company’s securities portfolio primarily consisted of securities issued by the U.S. government, U.S. government agencies, U.S. government-sponsored enterprises and state and municipalities. All of the Company’s mortgage-backed securities and collateralized mortgage obligations are issued by U.S. government agencies and U.S. government-sponsored enterprises and are implicitly guaranteed by the U.S. government. The Company had no other issuances in its portfolio which exceeded ten percent of shareholders’ equity.
	The following table summarizes the amortized cost, gross unrealized gains and losses and the resulting fair value of securities available for sale:
		Amortized			Gross			Gross			Fair Value
		Cost			Unrealized			Unrealized
					Gains			Losses
	December 31, 2014	(in thousands)
	U.S. government agency and government-sponsored enterprise mortgage-backed securities and collateralized mortgage obligations	$	1,160,378		$	10,219		$	(8,210	)	$	1,162,387
	State and municipal securities	483,578			14,432			(1,526		)	496,484
	U.S. government agency and government-sponsored enterprise securities	416,919			856			(4,069		)	413,706
	U.S. government securities	20,910			—			(411		)	20,499
	Other securities	5,284			20			(123		)	5,181
	Total	$	2,087,069		$	25,527		$	(14,339	)	$	2,098,257
	December 31, 2013
	U.S. government agency and government-sponsored enterprise mortgage-backed securities and collateralized mortgage obligations	$	961,442		$	10,640		$	(23,674	)	$	948,408
	State and municipal securities	357,013			11,450			(3,993		)	364,470
	U.S. government agency and government-sponsored enterprise securities	335,671			434			(10,066		)	326,039
	U.S. government securities	21,081			—			(967		)	20,114
	Other securities	5,284			27			(231		)	5,080
	Total	$	1,680,491		$	22,551		$	(38,931	)	$	1,664,111
	Proceeds from sales of securities available-for-sale were $63,292 thousand, $166,881 thousand and $95,165 thousand for the years ended December 31, 2014, 2013 and 2012, respectively. The following table provides the gross realized gains and losses on the sales and calls of securities for the periods indicated:
		Years Ended December 31,
		2014			2013			2012
		(in thousands)
	Gross realized gains	$	553		$	632		$	4,447
	Gross realized losses	(1		)	(170		)	(714		)
	Net realized gains	$	552		$	462		$	3,733
	The scheduled contractual maturities of investment securities available for sale at December 31, 2014 are presented as follows:
		December 31, 2014
		Amortized Cost			Fair Value
		(in thousands)
	Due within one year	$	18,872		$	19,028
	Due after one year through five years	426,532			426,035
	Due after five years through ten years	534,515			537,175
	Due after ten years	1,101,866			1,110,838
	Other securities with no stated maturity	5,284			5,181
	Total investment securities available-for-sale	$	2,087,069		$	2,098,257
	The following table summarizes the carrying value of securities pledged as collateral to secure public deposits, borrowings and other purposes as permitted or required by law:
		December 31, 2014			December 31, 2013
		(in thousands)
	Washington and Oregon State to secure public deposits	$	328,400		$	277,012
	Federal Reserve Bank to secure borrowings	41,146			42,694
	Other securities pledged	157,097			43,081
	Total securities pledged as collateral	$	526,643		$	362,787
	The following tables show the gross unrealized losses and fair value of the Company’s investments with unrealized losses that are not deemed to be other-than-temporarily impaired, aggregated by investment category and length of time that individual securities have been in a continuous unrealized loss position at December 31, 2014 and 2013:
		Less than 12 Months						12 Months or More						Total
		Fair			Unrealized			Fair			Unrealized			Fair		Unrealized
		Value			Losses			Value			Losses			Value		Losses
	December 31, 2014	(in thousands)
	U.S. government agency and government-sponsored enterprise mortgage-backed securities and collateralized mortgage obligations	$	258,825		$	(1,287	)	$	279,015		$	(6,924	)	$	537,840	(8,211		)
	State and municipal securities	71,026			(543		)	44,148			(982		)	115,174		(1,525		)
	U.S. government agency and government-sponsored enterprise securities	105,250			(518		)	216,221			(3,551		)	321,471		(4,069		)
	U.S. government securities	—			—			19,450			(411		)	19,450		(411		)
	Other securities	2,313			(2		)	2,834			(121		)	5,147		(123		)
	Total	$	437,414		$	(2,350	)	$	561,668		$	(11,989	)	$	999,082	$	(14,339	)
	December 31, 2013
	U.S. government agency and government-sponsored enterprise mortgage-backed securities and collateralized mortgage obligations	$	492,921		$	(10,991	)	$	121,303		$	(12,684	)	$	614,224	$	(23,675	)
	State and municipal securities	112,400			(3,069		)	13,815			(923		)	126,215		(3,992		)
	U.S. government agency and government-sponsored enterprise securities	260,001			(8,063		)	28,447			(2,003		)	288,448		(10,066		)
	U.S. government securities	20,114			(967		)	—			—			20,114		(967		)
	Other securities	2,257			(58		)	2,783			(173		)	5,040		(231		)
	Total	$	887,693		$	(23,148	)	$	166,348		$	(15,783	)	$	1,054,041	$	(38,931	)
	At December 31, 2014, there were 125 U.S. government agency and government-sponsored enterprise mortgage-backed securities and collateralized mortgage obligations securities in an unrealized loss position, of which 43 were in a continuous loss position for 12 months or more. The decline in fair value is attributable to changes in interest rates relative to where these investments fall within the yield curve and their individual characteristics. Because the Company does not currently intend to sell these securities nor does the Company consider it more likely than not that it will be required to sell these securities before the recovery of amortized cost basis, which may be upon maturity, the Company does not consider these investments to be other-than-temporarily impaired at December 31, 2014.
	At December 31, 2014, there were 95 state and municipal government securities in an unrealized loss position, of which 44 were in a continuous loss position for 12 months or more. The unrealized losses on state and municipal securities were caused by interest rate changes or widening of market spreads subsequent to the purchase of the individual securities. Management monitors published credit ratings of these securities for adverse changes. As of December 31, 2014 none of the rated obligations of state and local government entities held by the Company had a below investment grade credit rating. Because the credit quality of these securities are investment grade and the Company does not currently intend to sell these securities nor does the Company consider it more likely than not that it will be required to sell these securities before the recovery of amortized cost basis, which may be upon maturity, the Company does not consider these investments to be other-than-temporarily impaired at December 31, 2014.
At December 31, 2014, there were 34 U.S. government agency and government-sponsored enterprise securities in an unrealized loss position, of which 17 were in a continuous loss position for 12 months or more. The decline in fair value is attributable to changes in interest rates relative to where these investments fall within the yield curve and their individual characteristics. Because the Company does not currently intend to sell these securities nor does the Company consider it more likely than not that it will be required to sell these securities before the recovery of amortized cost basis, which may be upon maturity, the Company does not consider these investments to be other-than-temporarily impaired at December 31, 2014.
At December 31, 2014, there were two U.S. government securities in an unrealized loss position, both of which were in a continuous loss position for 12 months or more. The decline in fair value is attributable to changes in interest rates relative to where these investments fall within the yield curve and their individual characteristics. Because the Company does not currently intend to sell these securities nor does the Company consider it more likely than not that it will be required to sell these securities before the recovery of amortized cost basis, which may be upon maturity, the Company does not consider these investments to be other-than-temporarily impaired at December 31, 2014.
At December 31, 2014, there were two other securities in an unrealized loss position, of which one security, a mortgage-backed securities fund was in a continuous unrealized loss position for 12 months or more. The decline in fair value is attributable to changes in interest rates and the additional risk premium investors are demanding for investment securities with these characteristics. The Company does not consider this investment to be other-than-temporarily impaired at December 31, 2014 as it has the intent and ability to hold the investment for sufficient time to allow for recovery in the market value.
Securities Deemed to be Other-Than-Temporarily Impaired
During the fourth quarter of 2012, the Company received full payment on a municipal bond that was determined to be other-than-temporarily impaired during 2011 for which the Company recorded impairment of $3.0 million in 2011. The 2012 gain related to this security is recorded in the line item Investment securities gains(losses), net in the Consolidated Statements of Income.

Loans

Loans	12 Months Ended
	Dec. 31, 2014
Loans Receivable, Net [Abstract]
Financing Receivables [Text Block]	Loans
	The Company’s loan portfolio includes originated and purchased loans. Originated loans and purchased loans for which there was no evidence of credit deterioration at their acquisition date and it was probable that we would be able to collect all contractually required payments are referred to collectively as loans, excluding purchased credit impaired loans. Purchased loans for which there was, at acquisition date, evidence of credit deterioration since their origination and it was probable that we would be unable to collect all contractually required payments are referred to as purchased credit impaired loans, or “PCI loans.”
	The following is an analysis of the loan portfolio by major types of loans (net of unearned income):
		December 31, 2014												December 31, 2013
		Loans, excluding PCI loans				PCI Loans				Total				Loans, excluding PCI loans				PCI Loans				Total
		(in thousands)
	Commercial business	$	2,119,565			$	44,505			$	2,164,070			$	1,561,782			$	60,942			$	1,622,724
	Real estate:
	One-to-four family residential	175,571				26,993				202,564				108,317				33,943				142,260
	Commercial and multifamily residential	2,363,541				128,769				2,492,310				2,080,075				154,191				2,234,266
	Total real estate	2,539,112				155,762				2,694,874				2,188,392				188,134				2,376,526
	Real estate construction:
	One-to-four family residential	116,866				4,021				120,887				54,155				13,313				67,468
	Commercial and multifamily residential	134,443				2,321				136,764				126,390				5,373				131,763
	Total real estate construction	251,309				6,342				257,651				180,545				18,686				199,231
	Consumer	364,182				23,975				388,157				357,014				30,083				387,097
	Less: Net unearned income	(59,374		)		—				(59,374		)		(68,282		)		—				(68,282		)
	Total loans, net of unearned income	5,214,794				230,584				5,445,378				4,219,451				297,845				4,517,296
	Less: Allowance for loan and lease losses	(53,233		)		(16,336		)		(69,569		)		(52,280		)		(20,174		)		(72,454		)
	Total loans, net	$	5,161,561			$	214,248			$	5,375,809			$	4,167,171			$	277,671			$	4,444,842
	Loans held for sale	$	1,116			$	—			$	1,116			$	735			$	—			$	735
	At December 31, 2014 and 2013, the Company had no material foreign activities. Substantially all of the Company’s loans and unfunded commitments are geographically concentrated in its service areas within the states of Washington, Oregon, and Idaho.
	The Company has granted loans to officers and directors of the Company and related interests. These loans are made on the same terms, including interest rates and collateral, as those prevailing at the time for comparable transactions with unrelated persons and do not involve more than the normal risk of collectability. The aggregate dollar amount of these loans was $13.2 million and $14.2 million at December 31, 2014 and 2013, respectively. During 2014, advances on related party loans totaled $5.7 million and repayments on related party loans totaled $6.7 million.
	At December 31, 2014 and 2013, $1.08 billion of commercial and residential real estate loans were pledged as collateral on Federal Home Loan Bank advances. The Company has also pledged $46.0 million and $45.2 million of commercial loans to the Federal Reserve Bank for additional borrowing capacity at December 31, 2014 and 2013, respectively.
	Nonaccrual loans totaled $31.4 million and $34.0 million at December 31, 2014 and 2013, respectively. The amount of interest income foregone as a result of these loans being placed on nonaccrual status totaled $2.2 million for 2014, $2.9 million for 2013 and $3.4 million for 2012. There were $1.4 million in loans 90 days past due and still accruing interest as of December 31, 2014 and no loans 90 days past due and still accruing interest as of December 31, 2013. At December 31, 2014 and 2013, there were $349 thousand and $28 thousand, respectively, of commitments of additional funds for loans accounted for on a nonaccrual basis.
	The following is an analysis of nonaccrual loans as of December 31, 2014 and 2013:
		December 31, 2014								December 31, 2013
		Recorded				Unpaid Principal				Recorded				Unpaid Principal
		Investment				Balance				Investment				Balance
		Nonaccrual				Nonaccrual				Nonaccrual				Nonaccrual
		Loans				Loans				Loans				Loans
		(in thousands)
	Commercial business:
	Secured	$	16,552			$	21,453			$	12,433			$	19,186
	Unsecured	247				269				176				202
	Real estate:
	One-to-four family residential	2,822				5,680				2,667				4,678
	Commercial and multifamily residential:
	Commercial land	821				1,113				442				783
	Income property	3,200				5,521				4,267				5,383
	Owner occupied	3,826				5,837				6,334				7,486
	Real estate construction:
	One-to-four family residential:
	Land and acquisition	95				112				3,246				6,601
	Residential construction	370				370				459				1,928
	Commercial and multifamily residential:
	Owner occupied	480				489				—				—
	Consumer	2,939				3,930				3,991				6,187
	Total	$	31,352			$	44,774			$	34,015			$	52,434
	Loans, excluding purchased credit impaired loans
	The following is an aging of the recorded investment of the loan portfolio as of December 31, 2014 and 2013:
		Current				30 - 59				60 - 89				Greater				Total				Nonaccrual			Total Loans
		Loans				Days				Days				than 90				Past Due				Loans
						Past Due				Past Due				Days Past
														Due
	December 31, 2014	(in thousands)
	Commercial business:
	Secured	$	2,004,418			$	5,137			$	6,149			$	1,372			$	12,658			$	16,552		$	2,033,628
	Unsecured	79,661				185				—				—				185				247			80,093
	Real estate:
	One-to-four family residential	167,197				1,700				45				—				1,745				2,822			171,764
	Commercial and multifamily residential:
	Commercial land	187,470				1,454				34				—				1,488				821			189,779
	Income property	1,294,982				3,031				786				—				3,817				3,200			1,301,999
Owner occupied	839,689				937				289				—				1,226				3,826			844,741
Real estate construction:
One-to-four family residential:
Land and acquisition	15,462				953				—				—				953				95			16,510
Residential construction	97,821				326				—				4				330				370			98,521
Commercial and multifamily residential:
Income property	73,783				—				—				—				—				—			73,783
Owner occupied	57,470				—				994				—				994				480			58,944
Consumer	341,032				933				118				10				1,061				2,939			345,032
Total	$	5,158,985			$	14,656			$	8,415			$	1,386			$	24,457			$	31,352		$	5,214,794
	Current				30 - 59				60 - 89				Greater				Total				Nonaccrual			Total Loans
	Loans				Days				Days				than 90				Past Due				Loans
					Past Due				Past Due				Days Past
													Due
December 31, 2013	(in thousands)
Commercial business:
Secured	$	1,457,820			$	12,713			$	681			$	—			$	13,394			$	12,433		$	1,483,647
Unsecured	72,255				156				17				—				173				176			72,604
Real estate:
One-to-four family residential	100,591				1,993				641				—				2,634				2,667			105,892
Commercial and multifamily residential:
Commercial land	142,034				—				358				—				358				442			142,834
Income property	1,138,732				144				3,289				—				3,433				4,267			1,146,432
Owner occupied	749,561				4,714				—				—				4,714				6,334			760,609
Real estate construction:
One-to-four family residential:
Land and acquisition	8,225				199				—				—				199				3,246			11,670
Residential construction	41,533				—				—				—				—				459			41,992
Commercial and multifamily residential:
Income property	86,521				—				—				—				—				—			86,521
Owner occupied	38,916				—				—				—				—				—			38,916
Consumer	322,685				835				823				—				1,658				3,991			328,334
Total	$	4,158,873			$	20,754			$	5,809			$	—			$	26,563			$	34,015		$	4,219,451
The following is an analysis of the impaired loans (see Note 1) as of December 31, 2014 and 2013:
	Recorded Investment				Recorded Investment				Impaired Loans With												Impaired Loans Without
	of Loans				of Loans				Recorded Allowance												Recorded Allowance
	Collectively Measured				Individually
	for Contingency				Measured for
	Provision				Specific
					Impairment				Recorded				Unpaid				Related				Recorded			Unpaid
									Investment				Principal				Allowance				Investment			Principal
													Balance											Balance
December 31, 2014	(in thousands)
Commercial business:
Secured	$	2,023,104			$	10,524			$	99			$	99			$	25			$	10,425		$	12,410
Unsecured	80,091				2				2				2				2				—			—
Real estate:
One-to-four family residential	169,619				2,145				424				465				120				1,721			2,370
Commercial and multifamily residential:
Commercial land	189,779				—				—				—				—				—			—
Income property	1,295,650				6,349				—				—				—				6,349			10,720
Owner occupied	835,895				8,846				582				582				27				8,264			12,732
Real estate construction:
One-to-four family residential:
Land and acquisition	16,401				109				109				109				67				—			—
Residential construction	98,521				—				—				—				—				—			—
Commercial and multifamily residential:
Income property	73,783				—				—				—				—				—			—
Owner occupied	58,944				—				—				—				—				—			—
Consumer	344,908				124				—				—				—				124			201
Total	$	5,186,695			$	28,099			$	1,216			$	1,257			$	241			$	26,883		$	38,433
	Recorded Investment				Recorded Investment				Impaired Loans With												Impaired Loans Without
	of Loans				of Loans				Recorded Allowance												Recorded Allowance
	Collectively Measured				Individually
	for Contingency				Measured for
	Provision				Specific
					Impairment				Recorded				Unpaid				Related				Recorded			Unpaid
									Investment				Principal				Allowance				Investment			Principal
													Balance											Balance
December 31, 2013	(in thousands)
Commercial business:
Secured	$	1,478,560			$	5,087			$	2,866			$	2,885			$	343			$	2,221		$	2,560
Unsecured	72,569				35				35				35				35				—			—
Real estate:
One-to-four family residential	104,272				1,620				442				479				138				1,178			2,119
Commercial and multifamily residential:
Commercial land	142,719				115				—				—				—				115			398
Income property	1,140,019				6,413				918				933				26				5,495			7,885
Owner occupied	749,601				11,008				3,802				3,817				1,073				7,206			10,464
Real estate construction:
One-to-four family residential
Land and acquisition	9,726				1,944				113				113				71				1,831			2,587
Residential construction	41,992				—				—				—				—				—			—
Commercial and multifamily residential:
Income property	86,521				—				—				—				—				—			—
Owner occupied	38,916				—				—				—				—				—			—
Consumer	328,167				167				23				27				4				144			210
Total	$	4,193,062			$	26,389			$	8,199			$	8,289			$	1,690			$	18,190		$	26,223
The following table provides additional information on impaired loans for the years ended December 31, 2014, 2013 and 2012:
	Year ended December 31, 2014								Year Ended December 31, 2013								Year ended December 31, 2012
	Average Recorded				Interest Recognized				Average Recorded				Interest Recognized				Average Recorded				Interest Recognized
	Investment				on				Investment				on				Investment				on
	Impaired Loans				Impaired Loans				Impaired Loans				Impaired Loans				Impaired Loans				Impaired Loans
	(in thousands)
Commercial business
Secured	$	7,345			$	36			$	5,636			$	19			$	8,978			$	9
Unsecured	19				1				61				3				113				6
Real estate:
One-to-four family residential	2,094				49				1,665				63				2,130				—
Commercial & multifamily residential
Commercial land	82				—				1,691				—				3,124				—
Income property	6,782				270				8,910				238				7,895				77
Owner occupied	9,472				956				10,779				971				13,315				1,004
Real estate construction:
One-to-four family residential
Land and acquisition	694				6				2,624				6				4,465				—
Residential construction	—				—				420				—				3,223				11
Commercial & multifamily residential
Income property	—				—				—				—				3,169				—
Consumer	147				9				253				6				1,112				7
Total	$	26,635			$	1,327			$	32,039			$	1,306			$	47,524			$	1,114
The following is an analysis of loans classified as troubled debt restructurings (“TDR”) for the years ended December 31, 2014, 2013 and 2012:
	Year ended December 31, 2014											Year Ended December 31, 2013											Year ended December 31, 2012
	Number of TDR Modifications			Pre-Modification				Post-Modification				Number of TDR Modifications			Pre-Modification				Post-Modification				Number of TDR Modifications		Pre-Modification		Post-Modification
				Outstanding				Outstanding							Outstanding				Outstanding						Outstanding		Outstanding
				Recorded				Recorded							Recorded				Recorded						Recorded		Recorded
				Investment				Investment							Investment				Investment						Investment		Investment
	(dollars in thousands)
Commercial business:
Secured	4			$	759			$	759			2			$	190			$	190			1		$	195	$	194
Real estate:
One-to-four family residential	2			494				494				1			113				113				—		—		—
Commercial and multifamily residential:
Commercial land	—			—				—				1			137				137				—		—		—
Income property	1			143				126				4			1,186				1,186				1		4,279		2,650
Owner occupied	1			1,496				1,496				1			172				172				—		—		—
Real estate construction:
One-to-four family residential:
Land and acquisition	—			—				—				1			117				117				—		—		—
Consumer	—			—				—				2			53				53				—		—		—
Total	8			$	2,892			$	2,875			12			$	1,968			$	1,968			2		$	4,474	$	2,844
The Company’s loans classified as TDR are loans that have been modified or the borrower has been granted special concessions due to financial difficulties, that if not for the challenges of the borrower, the Company would not otherwise consider. The Company had no commitments to lend additional funds on loans classified as TDR as of December 31, 2014 and 2013. The TDR modifications or concessions are made to increase the likelihood that these borrowers with financial difficulties will be able to satisfy their debt obligations as amended. Credit losses for loans classified as TDR are measured on the same basis as impaired loans. For impaired loans, an allowance is established when the collateral value less selling costs (or discounted cash flows or observable market price) of the impaired loan is lower than the recorded investment of that loan. The Company did not have any loans modified as TDR that defaulted within 12 months of being modified as TDR during the years ended December 31,
2014, 2013, and 2012.
Purchased Credit Impaired Loans (“PCI Loans”)
PCI loans are accounted for under ASC 310-30 and initially measured at fair value based on expected future cash flows over the life of the loans. Loans that have common risk characteristics are aggregated into pools. The Company remeasures contractual and expected cash flows, at the pool-level, on a quarterly basis.
Contractual cash flows are calculated based upon the loan pool terms after applying a prepayment factor. Calculation of the applied prepayment factor for contractual cash flows is the same as described below for expected cash flows.
Inputs to the determination of expected cash flows include cumulative default and prepayment data as well as loss severity and recovery lag information. Cumulative default and prepayment data are calculated via a transition matrix. The transition matrix is a matrix of probability values that specifies the probability of a loan pool transitioning into a particular delinquency state (e.g. 0-30 days past due, 31 to 60 days, etc.) given its delinquency state at the remeasurement date. Loss severity factors are based upon either actual charge-off data within the loan pools or industry averages and recovery lags are based upon the collateral within the loan pools.
The excess of cash flows expected to be collected over the initial fair value of acquired impaired loans is referred to as the accretable yield and is accreted into interest income over the estimated life of the acquired loans using the effective yield method. Other adjustments to the accretable yield include changes in the estimated remaining life of the acquired loans, changes in expected cash flows and changes of indices for acquired loans with variable interest rates.
The following is an analysis of our PCI loans, net of related allowance for losses as of December 31, 2014 and 2013:
	December 31, 2014				December 31, 2013
	(in thousands)
Commercial business	$	50,334			$	72,870
Real estate:
One-to-four family residential	31,981				41,642
Commercial and multifamily residential	140,398				170,879
Total real estate	172,379				212,521
Real estate construction:
One-to-four family residential	4,353				14,781
Commercial and multifamily residential	2,588				6,869
Total real estate construction	6,941				21,650
Consumer	26,814				34,101
Subtotal of purchased credit impaired loans	256,468				341,142
Less:
Valuation discount resulting from acquisition accounting	25,884				43,297
Allowance for loan losses	16,336				20,174
PCI loans, net of valuation discounts and allowance for loan losses	$	214,248			$	277,671
The following table shows the changes in accretable yield for acquired loans for the years ended December 31, 2014, 2013, and 2012:
	Years Ended December 31,
	2014				2013				2012
	(in thousands)
Balance at beginning of period	$	103,907			$	166,888			$	259,669
Accretion	(36,066		)		(51,816		)		(86,671		)
Disposals	(3,386		)		(6,898		)		(12,856		)
Reclassifications from nonaccretable difference	9,394				(4,267		)		6,746
Balance at end of period	$	73,849			$	103,907			$	166,888
The Company did not acquire any loans accounted for under ASC 310-30 during 2014 or 2013.

Allowance_for_Loan_and_Lease_L

Allowance for Loan and Lease Losses and Unfunded Commitments and Letters of Credit	12 Months Ended
	Dec. 31, 2014
Allowance For Loan And Lease Losses And Unfunded Loan Commitments And Letters Of Credit
Allowance for Loan and Lease Losses and Unfunded Loan Commitments and Letters of Credit	Allowance for Loan and Lease Losses and Unfunded Commitments and Letters of Credit
	Loans, excluding PCI loans
	We maintain an allowance for loan and lease losses (“ALLL”) to absorb losses inherent in the loan portfolio. The size of the ALLL is determined through quarterly assessments of the probable estimated losses in the loan portfolio. Our methodology for making such assessments and determining the adequacy of the ALLL includes the following key elements:
	1	General valuation allowance consistent with the Contingencies topic of the FASB ASC.
	2	Classified loss reserves on specific relationships. Specific allowances for identified problem loans are determined in accordance with the Receivables topic of the FASB ASC.
	3	The unallocated allowance provides for other factors inherent in our loan portfolio that may not have been contemplated in the general and specific components of the allowance. This unallocated amount generally comprises less than 5% of the allowance. The unallocated amount is reviewed quarterly based on trends in credit losses, the results of credit reviews and overall economic trends.
	The general valuation allowance is calculated quarterly using quantitative and qualitative information about specific loan classes. The minimum required level with respect to which an entity develops a methodology to determine its allowance for loan and lease losses is by general categories of loans, such as commercial business, real estate, and consumer. However, the Company’s methodology in determining its allowance for loan and lease losses is prepared in a more detailed manner at the loan class level, utilizing specific categories such as commercial business secured, commercial business unsecured, real estate commercial land, and real estate income property multifamily. The quantitative information uses historical losses from a specific loan class and incorporates the loan’s risk rating migration from origination to the point of loss based upon the consideration of an appropriate look back period.
	A loan’s risk rating is primarily determined based upon the borrower’s ability to fulfill its debt obligation from a cash flow perspective. In the event there is financial deterioration of the borrower, the borrower’s other sources of income or repayment are also considered, including recent appraisal values for collateral dependent loans. The qualitative information takes into account general economic and business conditions affecting our marketplace, seasoning of the loan portfolio, duration of the business cycle, etc. to ensure our methodologies reflect the current economic environment and other factors as using historical loss information exclusively may not give an accurate estimate of inherent losses within the Company’s loan portfolio.
	When a loan is deemed to be impaired, the Company has to determine if a specific valuation allowance is required for that loan. The specific valuation allowance is a reserve, calculated at the individual loan level, for each loan determined to be both, impaired and containing a value less than its recorded investment. The Company measures the impairment based on the discounted expected future cash flows, observable market price, or the fair value of the collateral less selling costs if the loan is collateral dependent or if foreclosure is probable. The specific reserve for each loan is equal to the difference between the recorded investment in the loan and its determined impairment value.
	The ALLL is increased by provisions for loan and lease losses (“provision”) charged to expense, and is reduced by loans charged off, net of recoveries. While the Company’s management believes the best information available is used to determine the ALLL, changes in market conditions could result in adjustments to the ALLL, affecting net income, if circumstances differ from the assumptions used in determining the ALLL.
	We have used the same methodology for ALLL calculations during 2014, 2013 and 2012. Adjustments to the percentages of the ALLL allocated to loan categories are made based on trends with respect to delinquencies and problem loans within each class of loans. The Company reviews the ALLL quantitative and qualitative methodology on a quarterly basis and makes adjustments when appropriate. The Company continues to strive towards maintaining a conservative approach to credit quality and will continue to make revisions to our ALLL as necessary to maintain adequate reserves. The Company carefully monitors the loan portfolio and continues to emphasize the importance of credit quality.
	Once it is determined that all or a portion of a loan balance is uncollectable, and the amount can be reasonably estimated, the uncollectable portion of the loan is charged-off.
	PCI Loans
	Purchased credit impaired loans that have common risk characteristics are aggregated into loan pools. When required, we record impairment, at the pool-level, to adjust the pool’s carrying value to its net present value of expected future cash flows. Quarterly, we re-measure expected loan pool cash flows. If, due to credit deterioration, the present value of expected cash flows is less than carrying value, we reduce the loan pool’s carrying value by adjusting the allowance for loan losses with an impairment charge to earnings which is recorded as provision for loan losses. If credit quality improves and the present value of expected cash flows exceeds carrying value, we increase the loan pool’s carrying value by recapturing previously recorded allowance for loan losses, if any. See Note 5, Loans, for further discussion of the accounting for PCI loans.
	Credit losses attributable to draws on purchased credit impaired loans, advanced subsequent to the loan purchase date, are accounted for under ASC 450-20 and those amounts are also subject to the Company’s internal and external credit review. An allowance for loan losses is estimated in a similar manner as the loan portfolio, excluding PCI loans, and a provision for loan losses is charged to earnings as necessary.
	The following tables show a detailed analysis of the allowance for loan and lease losses for loans for the years ended December 31, 2014, 2013 and 2012:
			Beginning		Charge-offs			Recoveries		Provision (Recovery)			Ending		Specific		General
			Balance										Balance		Reserve		Allocation
	Year ended December 31, 2014		(in thousands)
	Commercial business:
	Secured		$	31,027	$	(4,159	)	$	2,637	$	(3,582	)	$	25,923	$	25	$	25,898
	Unsecured		696		(130		)	370		(9		)	927		2		925
	Real estate:
	One-to-four family residential		1,252		(230		)	159		1,100			2,281		120		2,161
	Commercial and multifamily residential:
	Commercial land		489		(29		)	70		269			799		—		799
	Income property		9,234		(1,934		)	819		1,040			9,159		—		9,159
	Owner occupied		3,605		(1,030		)	51		2,381			5,007		27		4,980
	Real estate construction:
	One-to-four family residential:
	Land and acquisition		610		—			740		(153		)	1,197		67		1,130
	Residential construction		822		—			1,190		(152		)	1,860		—		1,860
	Commercial and multifamily residential:
	Income property		285		—			—		337			622		—		622
	Owner occupied		58		—			—		376			434		—		434
	Consumer		2,547		(2,774		)	1,353		2,054			3,180		—		3,180
	Purchased credit impaired		20,174		(14,436		)	7,721		2,877			16,336		—		16,336
	Unallocated		1,655		—			—		189			1,844		—		1,844
	Total		$	72,454	$	(24,722	)	$	15,110	$	6,727		$	69,569	$	241	$	69,328
			Beginning		Charge-offs			Recoveries		Provision (Recovery)			Ending		Specific		General
			Balance										Balance		Reserve		Allocation
	Year Ended December 31, 2013		(in thousands)
	Commercial business:
	Secured		$	27,270	$	(4,148	)	$	1,512	$	6,393		$	31,027	$	343	$	30,684
	Unsecured		753		(794		)	932		(195		)	696		35		661
	Real estate:
	One-to-four family residential		694		(228		)	270		516			1,252		138		1,114
	Commercial and multifamily residential:
	Commercial land		460		(20		)	169		(120		)	489		—		489
	Income property		11,033		(1,405		)	489		(883		)	9,234		26		9,208
	Owner occupied		6,362		(1,118		)	375		(2,014		)	3,605		1,073		2,532
	Real estate construction:
	One-to-four family residential:
	Land and acquisition		1,171		(32		)	2,553		(3,082		)	610		71		539
	Residential construction		635		(101		)	112		176			822		—		822
	Commercial and multifamily residential:
	Income property		316		—			—		(31		)	285		—		285
	Owner occupied		102		—			—		(44		)	58		—		58
	Consumer		2,437		(2,242		)	552		1,800			2,547		4		2,543
	Purchased credit impaired		30,056		(13,853		)	7,232		(3,261		)	20,174		—		20,174
	Unallocated		1,011		—			—		644			1,655		—		1,655
	Total		$	82,300	$	(23,941	)	$	14,196	$	(101	)	$	72,454	$	1,690	$	70,764
			Beginning		Charge-offs			Recoveries		Provision (Recovery)			Ending		Specific		General
			Balance										Balance		Reserve		Allocation
Year ended December 31, 2012		(in thousands)
Commercial business:
Secured		$	24,745	$	(10,029	)	$	1,354	$	11,200		$	27,270	$	113	$	27,157
Unsecured		689		(144		)	194		14			753		92		661
Real estate:
One-to-four family residential		654		(549		)	285		304			694		112		582
Commercial and multifamily residential:
Commercial land		488		(526		)	63		435			460		—		460
Income property		9,551		(4,030		)	905		4,607			11,033		1,040		9,993
Owner occupied		9,606		(918		)	631		(2,957		)	6,362		38		6,324
Real estate construction:
One-to-four family residential:
Land and acquisition		2,331		(989		)	1,059		(1,230		)	1,171		—		1,171
Residential construction		864		(617		)	429		(41		)	635		—		635
Commercial and multifamily residential:
Income property		665		(93		)	66		(322		)	316		—		316
Owner occupied		35		—			—		67			102		—		102
Consumer		2,719		(2,534		)	1,171		1,081			2,437		—		2,437
Purchased credit impaired		4,944		(5,112		)	4,332		25,892			30,056		—		30,056
Unallocated		694		—			—		317			1,011		—		1,011
Total		$	57,985	$	(25,541	)	$	10,489	$	39,367		$	82,300	$	1,395	$	80,905
Changes in the allowance for unfunded commitments and letters of credit, a component of other liabilities in the consolidated balance sheet, are summarized as follows:
		Years Ended December 31,
		2014		2013			2012
		(in thousands)
Beginning balance		$	2,505	$	1,915		$	1,535
Net changes in the allowance for unfunded commitments and letters of credit		150		590			380
Ending balance		$	2,655	$	2,505		$	1,915
Risk Elements
The extension of credit in the form of loans or other credit products to individuals and businesses is one of our principal business activities. Our policies and applicable laws and regulations require risk analysis as well as ongoing portfolio and credit management. We manage our credit risk through lending limit constraints, credit review, approval policies and extensive, ongoing internal monitoring. We also manage credit risk through diversification of the loan portfolio by type of loan, type of industry, type of borrower and by limiting the aggregation of debt to a single borrower.
Risk ratings are reviewed and updated whenever appropriate, with more periodic reviews as the risk and dollar value of loss on the loan increases. In the event full collection of principal and interest is not reasonably assured, the loan is appropriately downgraded and, if warranted, placed on nonaccrual status even though the loan may be current as to principal and interest payments. Additionally, we assess whether an impairment of a loan warrants specific reserves or a write-down of the loan.
Pass loans are generally considered to have sufficient sources of repayment in order to repay the loan in full in accordance with all terms and conditions. Special mention loans have potential weaknesses that, if left uncorrected, may result in deterioration of the repayment prospects for the asset or in the Company’s credit position at some future date. Loans with a risk rating of Substandard or worse are reported as classified loans in our allowance for loan and lease losses analysis. We review these loans to assess the ability of our borrowers to service all interest and principal obligations and, as a result, the risk rating may be adjusted accordingly. Substandard loans reflect loans where a loss is possible if loan weaknesses are not corrected. Doubtful loans have a high probability of loss, however, the amount of loss has not yet been determined. Loss loans are considered uncollectable and when identified, are charged off.
The following is an analysis of the credit quality of our loan portfolio, excluding PCI loans as of December 31, 2014 and 2013:
		Pass		Special Mention			Substandard		Doubtful			Loss		Total
December 31, 2014		(in thousands)
Loans, excluding PCI loans
Commercial business:
Secured		$	1,963,210	$	15,790		$	54,628	$	—		$	—	$	2,033,628
Unsecured		79,534		—			559		—			—		80,093
Real estate:
One-to-four family residential		163,914		55			7,795		—			—		171,764
Commercial and multifamily residential:
Commercial land		183,701		4,217			1,861		—			—		189,779
Income property		1,287,729		5,885			8,385		—			—		1,301,999
Owner occupied		825,694		7,876			11,171		—			—		844,741
Real estate construction:
One-to-four family residential:
Land and acquisition		15,307		167			1,036		—			—		16,510
Residential construction		96,031		909			1,581		—			—		98,521
Commercial and multifamily residential:
Income property		73,783		—			—		—			—		73,783
Owner occupied		58,055		—			889		—			—		58,944
Consumer		339,695		68			5,269		—			—		345,032
Total		$	5,086,653	$	34,967		$	93,174	$	—		$	—	5,214,794
Less:
Allowance for loan losses														53,233
Loans, excluding PCI loans, net														$	5,161,561
		Pass		Special Mention			Substandard		Doubtful			Loss		Total
December 31, 2013		(in thousands)
Loans, excluding PCI loans
Commercial business:
Secured		$	1,372,038	$	43,309		$	68,300	$	—		$	—	$	1,483,647
Unsecured		72,226		199			179		—			—		72,604
Real estate:
One-to-four family residential		98,626		1,567			5,699		—			—		105,892
Commercial and multifamily residential:
Commercial land		137,850		—			4,984		—			—		142,834
Income property		1,108,033		5,473			32,926		—			—		1,146,432
Owner occupied		748,725		—			11,884		—			—		760,609
Real estate construction:
One-to-four family residential:
Land and acquisition		7,526		—			4,144		—			—		11,670
Residential construction		36,270		2,352			3,370		—			—		41,992
Commercial and multifamily residential:
Income property		86,206		—			315		—			—		86,521
Owner occupied		38,916		—			—		—			—		38,916
Consumer		321,348		331			6,188		467			—		328,334
Total		$	4,027,764	$	53,231		$	137,989	$	467		$	—	4,219,451
Less:
Allowance for loan losses														52,280
Loans, excluding PCI loans, net														$	4,167,171
The following is an analysis of the credit quality of our PCI loan portfolio as of December 31, 2014 and 2013:
		Pass		Special Mention			Substandard		Doubtful			Loss		Total
December 31, 2014		(in thousands)
PCI loans:
Commercial business:
Secured		$	37,927	$	937		$	9,223	$	—		$	—	$	48,087
Unsecured		2,156		—			91		—			—		2,247
Real estate:
One-to-four family residential		28,822		—			3,159		—			—		31,981
Commercial and multifamily residential:
Commercial land		9,104		—			6,240		—			—		15,344
Income property		51,435		1,892			7,186		—			—		60,513
Owner occupied		58,629		346			5,566		—			—		64,541
Real estate construction:
One-to-four family residential:
Land and acquisition		1,595		—			913		—			—		2,508
Residential construction		741		—			1,104		—			—		1,845
Commercial and multifamily residential:
Income property		1,435		—			227		—			—		1,662
Owner occupied		926		—			—		—			—		926
Consumer		24,037		—			2,777		—			—		26,814
Total		$	216,807	$	3,175		$	36,486	$	—		$	—	256,468
Less:
Valuation discount resulting from acquisition accounting														25,884
Allowance for loan losses														16,336
PCI loans, net														$	214,248
		Pass		Special Mention			Substandard		Doubtful			Loss		Total
December 31, 2013		(in thousands)
PCI loans:
Commercial business:
Secured		$	48,510	$	2,849		$	18,291	$	—		$	—	$	69,650
Unsecured		2,732		396			92		—			—		3,220
Real estate:
One-to-four family residential		35,066		1,842			4,734		—			—		41,642
Commercial and multifamily residential:
Commercial land		10,778		198			7,589		—			—		18,565
Income property		55,985		3,950			10,657		—			—		70,592
Owner occupied		67,653		111			13,958		—			—		81,722
Real estate construction:
One-to-four family residential:
Land and acquisition		4,674		2,739			1,936		—			—		9,349
Residential construction		3,008		—			2,424		—			—		5,432
Commercial and multifamily residential:
Income property		3,806		—			1,709		—			—		5,515
Owner occupied		1,074		—			280		—			—		1,354
Consumer		30,722		33			3,319		27			—		34,101
Total		$	264,008	$	12,118		$	64,989	$	27		$	—	341,142
Less:
Valuation discount resulting from acquisition accounting														43,297
Allowance for loan losses														20,174
PCI loans, net														$	277,671

Other_Real_Estate_Owned

Other Real Estate Owned	12 Months Ended
	Dec. 31, 2014
Other Real Estate, Foreclosed Assets, and Repossessed Assets [Abstract]
Other Real Estate Owned	Other Real Estate Owned
	The following table sets forth activity in OREO for the period:
		December 31, 2014			31-Dec-13
		(in thousands)
	Balance, beginning of period	$	35,927		$	26,987
	Established through acquisitions	2,752			14,708
	Transfers in, net of write-downs ($0 and $90, respectively)	10,200			18,100
	Additions to OREO	—			3,577
	Additional OREO write-downs	(4,039		)	(2,035		)
	Proceeds from sale of OREO property	(28,559		)	(35,949		)
	Net gain on sale of OREO	5,909			10,539
	Total OREO, end of period	$	22,190		$	35,927

FDIC_Losssharing_Asset_and_Cov

FDIC Loss-sharing Asset and Covered Assets	12 Months Ended
	Dec. 31, 2014
Covered Assets And FDIC Loss Sharing Asset
Covered Assets and FDIC Loss sharing Asset	FDIC Loss-sharing Asset and Covered Assets
	We are a party to four loss sharing agreements with the FDIC. Such agreements cover a substantial portion of losses incurred on acquired covered loans and other real estate owned. The loss-sharing agreements relate to the acquisitions of (1) Columbia River Bank in January 2010, (2) American Marine Bank in January 2010, (3) Summit Bank in May 2011, and (4) First Heritage Bank in May 2011. Under the terms of the loss-sharing agreements, the FDIC will absorb 80% of losses and share in 80% of loss recoveries up to specified amounts. With respect to loss-sharing agreements for two acquisitions completed in 2010, after those specified amounts, the FDIC will absorb 95% of losses and share in 95% of loss recoveries. The loss-sharing provisions of the agreements for commercial and single-family mortgage loans are in effect for five and ten years, respectively, from the acquisition dates and the loss recovery provisions are in effect for eight and ten years, respectively, from the acquisition dates.
	Ten years and forty-five days after the acquisition dates, the Bank must pay to the FDIC a clawback in the event the losses from the acquisitions fail to reach stated levels. The amount of the clawback is determined by a formula specified in each individual loss-sharing agreement. As of December 31, 2014 and 2013, the net present value of the Bank’s estimated clawback liability is $4.2 million and $3.9 million, respectively, which is included in other liabilities on the consolidated balance sheet.
	At December 31, 2014 and 2013, the FDIC loss-sharing asset is comprised of an FDIC indemnification asset of $13.1 million and $37.9 million, respectively, and an FDIC receivable of $2.1 million and $2.0 million, respectively. The indemnification represents the cash flows the Company expects to collect from the FDIC under the loss-sharing agreements and the FDIC receivable represents the reimbursable amounts from the FDIC that have not yet been received.
	For purchased credit impaired loans, the Company remeasures contractual and expected cash flows on a quarterly basis. When the quarterly remeasurement process results in a decrease in expected cash flows due to an increase in expected credit losses, impairment is recorded. As a result of this impairment, the indemnification asset is increased to reflect anticipated future cash to be received from the FDIC. Consistent with the loss-sharing agreements between the Company and the FDIC, the amount of the increase to the indemnification asset is measured as 80% of the resulting impairment.
	Alternatively, when the quarterly remeasurement results in an increase in expected future cash flows due to a decrease in expected credit losses, the nonaccretable difference decreases and the effective yield of the related loan portfolio is increased. As a result of the improved expected cash flows, the indemnification asset would be reduced first by the amount of any impairment previously recorded and, second, by increased amortization over the remaining life of the related loss-sharing agreement.
	The following table shows a detailed analysis of the FDIC loss-sharing asset for the years ending December 31, 2014 and 2013:
		2014			2013
		(in thousands)
	Balance at beginning of period	$	39,846		$	96,354
	Adjustments not reflected in income:
	Cash received from the FDIC, net	(2,499		)	(9,246		)
	FDIC reimbursable recoveries, net	(2,184		)	(2,245		)
	Adjustments reflected in income:
	Amortization, net	(21,279		)	(36,729		)
	Loan impairment (recapture)	2,301			(2,609		)
	Sale of other real estate	(2,179		)	(6,177		)
	Write-downs of other real estate	1,065			364
	Other	103			134
	Balance at end of period	$	15,174		$	39,846
	The following table presents information about the composition of the FDIC loss-sharing asset, the clawback liability, and the non-single family and the single family covered assets as of the date indicated:
		December 31, 2014
		Columbia River Bank			American Marine Bank			Summit Bank		First Heritage Bank		Total
		(in thousands)
	FDIC loss-sharing asset	$	1,183		$	4,927		$	4,712	$	4,352	$	15,174
	Clawback liability	$	4,017		$	157		$	—	$	—	$	4,174
	Non-single family covered assets	$	115,230		$	17,984		$	14,352	$	27,281	$	174,847
	Single family covered assets	$	11,166		$	26,587		$	6,530	$	2,516	$	46,799
	Loss-sharing expiration dates:
	Non-single family	First Quarter 2015			First Quarter 2015			Second Quarter 2016		Second Quarter 2016
	Single family	First Quarter 2020			First Quarter 2020			Second Quarter 2021		Second Quarter 2021
	Loss recovery expiration dates:
	Non-single family	First Quarter 2018			First Quarter 2018			Second Quarter 2019		Second Quarter 2019
	Single family	First Quarter 2020			First Quarter 2020			Second Quarter 2021		Second Quarter 2021

Premises_and_Equipment

Premises and Equipment	12 Months Ended
	Dec. 31, 2014
Property, Plant and Equipment [Abstract]
Premises and Equipment	Premises and Equipment
	Real and personal property and software, less accumulated depreciation and amortization, were as follows:
		December 31,
		2014			2013
		(in thousands)
	Land	$	52,338		$	48,992
	Buildings	103,240			94,878
	Leasehold improvements	21,199			14,254
	Furniture and equipment	28,486			29,465
	Vehicles	596			546
	Computer software	15,666			17,490
	Total cost	221,525			205,625
	Less accumulated depreciation and amortization	(49,435		)	(50,893		)
	Total	$	172,090		$	154,732
	Total depreciation and amortization expense was $10.9 million, $10.2 million, and $6.3 million, for the years ended December 31, 2014, 2013, and 2012, respectively.

Goodwill_and_Intangible_Assets

Goodwill and Intangible Assets	12 Months Ended
	Dec. 31, 2014
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill and Intangible Assets	Goodwill and Other Intangible Assets
	In accordance with the Intangibles – Goodwill and Other topic of the FASB ASC, goodwill is not amortized but is reviewed for potential impairment at the reporting unit level. Management analyzes its goodwill for impairment on an annual basis and between annual tests in certain circumstances such as upon material adverse changes in legal, business, regulatory and economic factors. An impairment loss is recorded to the extent that the carrying amount of goodwill exceeds its implied fair value. The Company performed an impairment assessment as of July 31, 2014 and concluded that there was no impairment. As of December 31, 2014 we determined there were no events or circumstances which would more likely than not reduce the fair value of our reporting unit below its carrying amount.
	The core deposit intangible (“CDI”) is evaluated for impairment if events and circumstances indicate a possible impairment. The CDI is amortized on an accelerated basis over an estimated life of 10 years.
	The following table sets forth activity for goodwill and other intangible assets for the period:
		Years Ended December 31,
		2014			2013			2012
		(in thousands)
	Total goodwill, beginning of period	$	343,952		$	115,554		$	115,554
	Established through acquisitions	38,585			228,398			—
	Total goodwill, end of period	382,537			343,952			115,554
	Other intangible assets, net
	Core deposit intangible:
	Gross core deposit intangible balance, beginning of period	47,698			32,441			32,441
	Accumulated amortization, beginning of period	(22,765		)	(16,720		)	(12,275		)
	Core deposit intangible, net, beginning of period	24,933			15,721			20,166
	Established through acquisitions	10,900			15,257			—
	CDI current period amortization	(6,293		)	(6,045		)	(4,445		)
	Total core deposit intangible, end of period	29,540			24,933			15,721
	Intangible assets not subject to amortization	919			919			—
	Other intangible assets, net at end of period	30,459			25,852			15,721
	Total goodwill and intangible assets, end of period	$	412,996		$	369,804		$	131,275
	The following table provides the estimated future amortization expense of core deposit intangibles for the succeeding five years:
	Years Ending December 31,	(in thousands)
	2015	$	6,882
	2016	5,945
	2017	4,913
	2018	3,855
	2019	2,951

Deposits

Deposits	12 Months Ended
	Dec. 31, 2014
Deposits [Abstract]
Deposits	Deposits
	Year-end deposits are summarized in the following table:
		December 31,
		2014		2013
		(in thousands)
	Core deposits:
	Demand and other noninterest-bearing	$	2,651,373	$	2,171,703
	Interest-bearing demand	1,304,258		1,170,006
	Money market	1,760,331		1,569,261
	Savings	615,721		496,444
	Certificates of deposit less than $100,000	288,261		288,943
	Total core deposits	6,619,944		5,696,357
	Certificates of deposit greater than $100,000	202,014		201,498
	Certificates of deposit insured through CDARS®	18,429		19,488
	Brokered money market accounts	83,402		41,765
	Subtotal	6,923,789		5,959,108
	Valuation adjustment resulting from acquisition accounting	933		367
	Total deposits	$	6,924,722	$	5,959,475
	Overdrafts of $1.3 million and $1.1 million were reclassified as loan balances at December 31, 2014 and 2013, respectively.
	The following table shows the amount and maturity of time deposits that had balances of $100,000 or greater:
	Years Ending December 31,	(in thousands)
	2015	$	162,828
	2016	40,375
	2017	8,069
	2018	3,822
	2019	3,982
	Thereafter	108
	Total	$	219,184

Federal_Home_Loan_Bank_and_Fed

Federal Home Loan Bank and Federal Reserve Bank Borrowings	12 Months Ended
	Dec. 31, 2014
Federal Home Loan Bank and Federal Reserve Bank Borrowings [Abstract]
Federal Home Loan Bank and Federal Reserve Bank Borrowings [Text Block]	Federal Home Loan Bank and Federal Reserve Bank Borrowings
	FEDERAL HOME LOAN BANK
	The Company has entered into borrowing arrangements with the FHLB of Seattle to borrow funds under a short-term floating rate cash management advance program and fixed-term loan agreements. All borrowings are secured by stock of the FHLB and a blanket pledge of qualifying loans receivable. At December 31, 2014 FHLB advances were scheduled to mature as follows:
		Federal Home Loan Bank Advances
		Fixed rate advances
		Weighted Average Rate			Amount
		(dollars in thousands)
	Within 1 year	0.27	%		$	210,000
	Over 1 through 5 years	5.66	%		1,000
	Due after 10 years	5.37	%		5,000
	Total				216,000
	Valuation adjustment from acquisition accounting				568
	Total				$	216,568
	The maximum, average outstanding and year-end balances and average interest rates on advances from the FHLB were as follows for the years ended December 31, 2014, 2013 and 2012:
		Years ended December 31,
		2014				2013			2012
		(dollars in thousands)
	Balance at end of year	$	216,568			$	36,606		$	6,644
	Average balance during the year	$	44,876			$	51,030		$	100,337
	Maximum month-end balance during the year	$	216,568			$	190,631		$	118,967
	Weighted average rate during the year	0.74		%		1.12		%	2.79		%
	Weighted average rate at December 31	0.41		%		1.09		%	5.42		%
	FHLB advances are collateralized by the following:
		December 31,
		2014				2013
		(in thousands)
	Recorded value of blanket pledge on loans receivable	$	1,083,879			$	1,075,389
	Total	$	1,083,879			$	1,075,389
	FHLB borrowing capacity	$	865,138			$	1,037,159
	FEDERAL RESERVE BANK
	The Company is also eligible to borrow under the Federal Reserve Bank’s primary credit program, including the Term Auction Facility auctions. All borrowings are secured by certain pledged available for sale investment securities.
	Although the Company has not had FRB borrowings in the last three years, the Company pledges securities and loans for borrowing capacity at the Federal Reserve Bank.
	The following table shows amounts pledged to the Federal Reserve Bank:
		December 31,
		2014				2013
		(in thousands)
	Fair value of investment securities	$	40,128			$	40,210
	Recorded value of pledged commercial loans	46,002				45,242
	Total	$	86,130			$	85,452
	Federal Reserve Bank borrowing capacity	$	86,130			$	85,452

Securities_Sold_Under_Agreemen

Securities Sold Under Agreements to Repurchase	12 Months Ended
	Dec. 31, 2014
Securities Sold under Agreements to Repurchase [Abstract]
Securities sold under agreements to repurchase	Securities Sold Under Agreements to Repurchase - Term
	The Company has entered into wholesale repurchase agreements with certain brokers. At December 31, 2014 and 2013, the Company held $25.0 million in wholesale repurchase agreements with an interest rate of 1.88%. Securities available for sale with a carrying amount of $28.4 million at December 31, 2014 were pledged as collateral for the repurchase agreement borrowings. The broker holds the securities while the Company continues to receive the principal and interest payments from the securities. Upon maturity of the agreement in 2018, the pledged securities will be returned to the Company.
	Securities Sold Under Agreements to Repurchase - Sweep
	These sweep repurchase agreements are generally short-term agreements. These agreements are treated as financing transactions and the obligations to repurchase securities sold are reflected as a liability in the consolidated financial statements. The dollar amount of securities underlying the agreements remains in the applicable asset account of the consolidated financial statements. These agreements had a balance of $80.1 million and a weighted average interest rate of 0.12% at December 31, 2014. All of these repurchase agreements in existence at December 31, 2014 mature on a daily basis. Securities available for sale with a carrying amount of $103.0 million at December 31, 2014 were pledged as collateral for the repurchase agreement borrowings related to the acquisition of Intermountain.

Other_Borrowings

Other Borrowings	12 Months Ended
	Dec. 31, 2014
Subordinated Borrowing [Line Items]
Subordinated Borrowings Disclosure [Text Block]	Other Borrowings
	On November 1, 2014, with its acquisition of Intermountain, the Company assumed $16.5 million of trust preferred obligations. The Company redeemed $8.3 million of these obligations on December 26, 2014. At December 31, 2014, the remaining $8.2 million of obligations bore interest at a rate of 3.03%, paid quarterly. Subsequent to year-end, on January 7, 2015, the Company redeemed the remaining trust preferred obligations.

Derivatives_and_Balance_Sheet_

Derivatives and Balance Sheet Offsetting	12 Months Ended
	Dec. 31, 2014
General Discussion of Derivative Instruments and Hedging Activities [Abstract]
Derivatives and Balance Sheet Offsetting	Derivatives and Balance Sheet Offsetting
	The Company periodically enters into certain commercial loan interest rate swap agreements in order to provide commercial loan customers the ability to convert from variable to fixed interest rates. Under these agreements, the Company enters into a variable-rate loan agreement with a customer in addition to a swap agreement. This swap agreement effectively converts the customer’s variable rate loan into a fixed rate. The Company then enters into a corresponding swap agreement with a third party in order to offset its exposure on the variable and fixed components of the customer agreement. As the interest rate swap agreements with the customers and third parties are not designated as hedges under the Derivatives and Hedging topic of the FASB ASC, the instruments are marked to market in earnings. The notional amount of open interest rate swap agreements at December 31, 2014 and 2013 was $215.6 million and $179.5 million, respectively. During 2014 a mark-to-market loss of $51 thousand was recorded to other noninterest expense. There was no earnings impact for the years ending December 31, 2013 and 2012.
	The following table presents the fair value and balance sheet classification of derivatives not designated as hedging instruments at December 31, 2014 and 2013:
		Asset Derivatives									Liability Derivatives
		2014						2013			2014						2013
	(in thousands)	Balance Sheet		Fair Value				Balance Sheet	Fair Value		Balance Sheet		Fair Value				Balance Sheet	Fair Value
		Location						Location			Location						Location
	Interest rate contracts	Other assets		$	11,800			Other assets	$	9,044	Other liabilities		$	11,851			Other liabilities	$	9,044
	The Company is party to interest rate swap agreements and repurchase agreements that are subject to enforceable master netting arrangements or similar agreements. Under these agreements, the Company may have the right to net settle multiple contracts with the same counterparty. The following tables show the gross interest rate swap agreements and repurchase agreements in the consolidated balance sheets and the respective collateral received or pledged in the form of other financial instruments, which are generally marketable securities. The collateral amounts in these tables are limited to the outstanding balances of the related asset or liability. Therefore, instances of overcollateralization are not shown.
		Gross Amounts of Recognized Assets/Liabilities				Gross Amounts Offset in the Consolidated Balance Sheets			Net Amounts of Assets/Liabilities Presented in the Consolidated Balance Sheets		Gross Amounts Not Offset in the Consolidated Balance Sheets
											Collateral Posted				Net Amount
	December 31, 2014	(in thousands)
	Assets
	Interest rate contracts	$	11,800			$	—		$	11,800	$	—			$	11,800
	Liabilities
	Interest rate contracts	$	11,851			$	—		$	11,851	$	(11,851	)		$	—
	Repurchase agreements	$	105,080			$	—		$	105,080	$	(105,080	)		$	—
	December 31, 2013
	Assets
	Interest rate contracts	$	9,044			$	—		$	9,044	$	—			$	9,044
	Liabilities
	Interest rate contracts	$	9,044			$	—		$	9,044	$	(9,044	)		$	—
	Repurchase agreements	$	25,000			$	—		$	25,000	$	(25,000	)		$	—

Employee_Benefit_Plans

Employee Benefit Plans	12 Months Ended
	Dec. 31, 2014
Compensation and Retirement Disclosure [Abstract]
Employee Benefit Plans	Employee Benefit Plans
	401(k) Plan
	The Company maintains defined contribution and profit sharing plans in conformity with the provisions of section 401(k) of the Internal Revenue Code. The Columbia Bank 401(k) and Profit Sharing Plan (the “401(k) Plan”), permits eligible Columbia Bank employees, those who are at least 18 years of age and have completed six months of service, to contribute up to 75% of their eligible compensation to the 401(k) Plan. On a per pay period basis the Company is required to match 50% of employee contributions up to 3% of each employee’s eligible compensation. The Company contributed $2.0 million during 2014, $1.9 million during 2013, and $1.4 million during 2012, in matching funds to the 401(k) Plan. Additionally, as determined annually by the board of directors of the Company, the 401(k) Plan provides for a non-matching discretionary profit sharing contribution. The Company’s discretionary profit sharing contributions were $4.4 million during 2014, $4.0 million during 2013 and $2.9 million during 2012.
	Employee Stock Purchase Plan
	The Company maintains an “Employee Stock Purchase Plan” (the “ESP Plan”) in which substantially all employees of the Company are eligible to participate. The ESP Plan provides participants the opportunity to purchase common stock of the Company at a discounted price. Under the ESP Plan, participants can purchase common stock of the Company for 90% of the lowest price on either the first or last day in each of two six month look-back periods. The look-back periods are January 1st through June 30th and July 1st through December 31st of each calendar year. The 10% discount is recognized by the Company as compensation expense and does not have a material impact on net income or earnings per common share. Participants of the ESP Plan purchased 34,168 shares for $904 thousand in 2014, 32,598 shares for $686 thousand in 2013 and 39,393 shares for $725 thousand in 2012. At December 31, 2014 there were 541,744 shares available for purchase under the ESP plan.
	Supplemental Compensation Plan
	The Company maintains supplemental compensation arrangements (“Unit Plans”) to provide benefits for certain employees. The Unit Plans generally vest over a 4-10 year period and provide a fixed annual benefit over a 5-10 year period. At December 31, 2014 and 2013 the liability associated with these plans was $4.8 million and $4.7 million, respectively. Expense associated with these plans for the years ended December 31, 2014, 2013 and 2012 was $588 thousand, $458 thousand and $677 thousand, respectively.
	Supplemental Executive Retirement Plan
	The Company maintains a supplemental executive retirement plan (the “SERP”), a nonqualified deferred compensation plan that provides retirement benefits to certain highly compensated executives. The SERP is unsecured and unfunded and there are no program assets. The SERP projected benefit obligation, which represents the vested net present value of future payments to individuals under the plan is accrued over the estimated remaining term of employment of the participants and has been determined by actuarial valuation using the “RP-2000 Annuity Mortality Table” for the mortality assumptions and discount rate of 5.10% for both 2014 and 2013. Additional assumptions and features of the plan are a normal retirement age of 65 and a 2% annual cost of living benefit adjustment. The projected benefit obligation is included in other liabilities on the Consolidated Balance Sheets.
	The following table reconciles the accumulated liability for the projected benefit obligation:
		December 31,
		2014			2013
		(in thousands)
	Balance at beginning of year	$	16,423		$	11,616
	Established through acquisitions	511			3,398
	Change in actuarial loss	—			2,212
	Benefit expense	1,325			1,880
	Benefit payments	(1,718		)	(2,683		)
	Balance at end of year	$	16,541		$	16,423
	The benefits expected to be paid in conjunction with the SERP are presented in the following table:
	Years Ending December 31,	(in thousands)
	2015	$	975
	2016	994
	2017	1,088
	2018	1,349
	2019	1,384
	2020 through 2024	9,580
	Total	$	15,370

Commitments_and_Contingent_Lia

Commitments and Contingent Liabilities	12 Months Ended
	Dec. 31, 2014
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingent Liabilities	Commitments and Contingent Liabilities
	Lease Commitments: The Company leases locations as well as equipment under various non-cancellable operating leases that expire between 2015 and 2045. The majority of the leases contain renewal options and provisions for increases in rental rates based on an agreed upon index or predetermined escalation schedule. As of December 31, 2014, minimum future rental payments, exclusive of taxes and other charges, of these leases were:
	Years Ending December 31,	(in thousands)
	2015	$	8,557
	2016	6,602
	2017	5,353
	2018	4,671
	2019	4,308
	Thereafter	18,121
	Total minimum payments	$	47,612
	Total rental expense on buildings and equipment, net of rental income of $756 thousand, $673 thousand and $639 thousand, was $8.3 million, $8.5 million and $4.5 million, for the years ended December 31, 2014, 2013 and 2012, respectively.
	Financial Instruments with Off-Balance Sheet Risk: In the normal course of business, the Company makes loan commitments (typically unfunded loans and unused lines of credit) and issues standby letters of credit to accommodate the financial needs of its customers.
	Standby letters of credit commit the Company to make payments on behalf of customers under specified conditions. Historically, no significant losses have been incurred by the Company under standby letters of credit. Both arrangements have credit risk essentially the same as that involved in extending loans to customers and are subject to the Company’s normal credit policies, including collateral requirements, where appropriate. At December 31, 2014 and 2013, the Company’s loan commitments amounted to $1.58 billion and $1.37 billion, respectively. Standby letters of credit were $36.7 million at both December 31, 2014 and 2013. In addition, commitments under commercial letters of credit used to facilitate customers’ trade transactions and other off-balance sheet liabilities amounted to $4.4 million and $2.7 million at December 31, 2014 and 2013, respectively.
	Legal Proceedings: The Company and its subsidiaries are from time to time defendants in and are threatened with various legal proceedings arising from their regular business activities. Management, after consulting with legal counsel, is of the opinion that the ultimate liability, if any, resulting from these pending or threatened actions and proceedings will not have a material effect on the financial statements of the Company.

Accumulated_Other_Comprehensiv

Accumulated Other Comprehensive Income	12 Months Ended
	Dec. 31, 2014
Accumulated Other Comprehensive Income [Abstract]
Comprehensive Income (Loss) Note [Text Block]	Accumulated Other Comprehensive Income
	The following table shows changes in accumulated other comprehensive income (loss) by component for the years ended December 31, 2014 and 2013:
		Unrealized Gains and Losses on Available-for-Sale Securities (1)			Unrealized Gains and Losses on Pension Plan Liability (1)			Total (1)
	Year ended December 31, 2014	(in thousands)
	Beginning balance	$	(10,108	)	$	(1,936	)	$	(12,044	)
	Other comprehensive income before reclassifications	17,922			—			17,922
	Amounts reclassified from accumulated other comprehensive income (2)	(352		)	95			(257		)
	Net current-period other comprehensive income	17,570			95			17,665
	Ending balance	$	7,462		$	(1,841	)	$	5,621
	Year Ended December 31, 2013
	Beginning balance	$	20,918		$	(769	)	$	20,149
	Other comprehensive loss before reclassifications	(30,727		)	(1,432		)	(32,159		)
	Amounts reclassified from accumulated other comprehensive income (2)	(299		)	265			(34		)
	Net current-period other comprehensive loss	(31,026		)	(1,167		)	(32,193		)
	Ending balance	$	(10,108	)	$	(1,936	)	$	(12,044	)
	__________
	(1) All amounts are net of tax. Amounts in parenthesis indicate debits.
	(2) See following table for details about these reclassifications.
	The following table shows details regarding the reclassifications from accumulated other comprehensive income for the years ended December 31, 2014 and :
		Amount Reclassified from Accumulated Other Comprehensive Income						Affected line Item in the Consolidated Statement of Income
		Years Ended
		December 31, 2014			December 31, 2013
		(in thousands)
	Unrealized gains and losses on available-for-sale securities	$	552		$	462		Investment securities gains, net
		552			462			Total before tax
		(200		)	(163		)	Income tax provision
		$	352		$	299		Net of tax
	Amortization of pension plan liability	$	(149	)	$	(400	)	Compensation and employee benefits
	actuarial losses
		(149		)	(400		)	Total before tax
		54			135			Income tax benefit
		$	(95	)	$	(265	)	Net of tax

Shareholders_Equity

Shareholders' Equity	12 Months Ended
	Dec. 31, 2014
Stockholders' Equity Note [Abstract]
Shareholders' Equity	Shareholders’ Equity
	Preferred Stock. In conjunction with the acquisition of West Coast, the Company issued 8,782 shares of mandatorily convertible cumulative participating preferred stock, Series B (“Series B Preferred Stock”). The Series B Preferred Stock is not subject to the operation of a sinking fund. The Series B Preferred Stock is not redeemable by the Company and is perpetual with no maturity. The holders of Series B Preferred Stock have no general voting rights. If the Company declares and pays a dividend to its common shareholders, it must declare and pay to its holders of Series B Preferred Stock, on the same date, a dividend in an amount per share of the Series B Preferred Stock that is intended to provide such holders dividends in the amount they would have received if shares of Series B Preferred Stock had been converted into common stock as of that date. The outstanding shares of Series B Preferred Stock are convertible into 102,363 shares of Company common stock.
	Warrants to Purchase Common Stock. In conjunction with the acquisition of West Coast, the Company issued Amended and Restated Warrants (the “Warrants”) to purchase shares of Company common stock at an exercise price of $8.58 per share. The Company’s Amended and Restated Warrants amended and restated the Class C Warrants previously issued by West Coast. The Warrants were immediately exercisable and will expire on October 23, 2016. At December 31, 2014, there were no remaining warrants outstanding. During the year ended December 31, 2014, 1,722,497 common shares were issued from the exercise of warrants.
	Dividends. On January 23, 2014, the Company declared a quarterly cash dividend of $0.12 per common share and common share equivalent for holders of preferred stock, payable on February 19, 2014 to shareholders of record as of the close of business on February 5, 2014.
	On April 23, 2014 the Company declared a quarterly cash dividend of $0.12 per common share and common share equivalent for holders of preferred stock, and a special cash dividend of $0.12 per common share and common share equivalent for holders of preferred stock, both payable on May 21, 2014 to shareholders of record at the close of business May 7, 2014.
	On July 23, 2014 the Company declared a quarterly cash dividend of $0.14 per common share and common share equivalent for holders of preferred stock, and a special cash dividend of $0.14 per common share and common share equivalent for holders of preferred stock, both payable on August 20, 2014 to shareholders of record at the close of business August 6, 2014.
	On October 23, 2014 the Company declared a quarterly cash dividend of $0.16 per share and common share equivalent for holders of preferred stock, and a special cash dividend of $0.14 per common share and common share equivalent for holders of preferred stock, both payable on November 19, 2014 to shareholders of record at the close of business October 31, 2014.
	Subsequent to year end, on January 29, 2015 the Company declared a quarterly cash dividend of $0.16 per share and common share equivalent for holders of preferred stock, and a special cash dividend of $0.14, both payable on February 25, 2015, to shareholders of record at the close of business on February 11, 2015.
	The payment of cash dividends is subject to federal regulatory requirements for capital levels and other restrictions. In addition, the cash dividends paid by Columbia Bank to the Company are subject to both federal and state regulatory requirements.
	Stock Repurchase Program
	In 2011, the board of directors authorized the repurchase of 2 million shares of Columbia common stock. The Company may purchase the shares from time to time in the open market or in private transactions, under conditions which allow such repurchases to be accretive to earnings per share while maintaining capital ratios that exceed the guidelines for a well-capitalized financial institution. No shares were repurchased under the stock repurchase program during 2014, 2013 or 2012.

Fair_Value_Accounting_and_Meas

Fair Value Accounting and Measurement	12 Months Ended
	Dec. 31, 2014
Fair Value Disclosures [Abstract]
Fair Value Accounting and Measurement	Fair Value Accounting and Measurement
	The Fair Value Measurements and Disclosures topic of the FASB ASC defines fair value, establishes a consistent framework for measuring fair value and expands disclosure requirements about fair value. We hold fixed and variable rate interest-bearing securities, investments in marketable equity securities and certain other financial instruments, which are carried at fair value. Fair value is determined based upon quoted prices when available or through the use of alternative approaches, such as matrix or model pricing, when market quotes are not readily accessible or available.
	The valuation techniques are based upon observable and unobservable inputs. Observable inputs reflect market data obtained from independent sources, while unobservable inputs reflect our own market assumptions. These two types of inputs create the following fair value hierarchy:
	Level 1 – Quoted prices for identical instruments in active markets that are accessible at the measurement date.
	Level 2 – Quoted prices for similar instruments in active markets; quoted prices for identical or similar instruments in markets that are not active; and model derived valuations whose inputs are observable or whose significant value drivers are observable.
	Level 3 – Prices or valuation techniques that require inputs that are both significant to the fair value measurement and unobservable.
	Fair values are determined as follows:
	Securities at fair value are priced using a combination of market activity, industry recognized information sources, yield curves, discounted cash flow models and other factors. These fair value calculations are considered a Level 2 input method under the provisions of the Fair Value Measurements and Disclosures topic of the FASB ASC for all securities other than U.S. Treasury notes, which are considered a Level 1 input method.
	Interest rate contract positions are valued in models, which use as their basis, readily observable market parameters and are classified within Level 2 of the valuation hierarchy.
	The following table sets forth the Company’s financial assets and liabilities that were accounted for at fair value on a recurring basis at December 31, 2014 and 2013 by level within the fair value hierarchy. Financial assets and liabilities are classified in their entirety based on the lowest level of input that is significant to the fair value measurement:
		Fair value  at		Fair Value Measurements at Reporting Date Using
		December 31, 2014		Level 1			Level 2		Level 3
		(in thousands)
	Assets
	Securities available for sale
	U.S. government agency and sponsored enterprise mortgage-back securities and collateralized mortgage obligations	$	1,162,387	$	—		$	1,162,387	$	—
	State and municipal securities	496,484		—			496,484		—
	U.S. government agency and government-sponsored enterprise securities	413,706		—			413,706		—
	U.S. government securities	20,499		20,499			—		—
	Other securities	5,181		—			5,181		—
	Total securities available for sale	$	2,098,257	$	20,499		$	2,077,758	$	—
	Other assets (Interest rate contracts)	$	11,800	$	—		$	11,800	$	—
	Liabilities
	Other liabilities (Interest rate contracts)	$	11,851	$	—		$	11,851	$	—
		Fair value  at		Fair Value Measurements at Reporting Date Using
		December 31, 2013		Level 1			Level 2		Level 3
		(in thousands)
	Assets
	Securities available for sale
	U.S. government agency and sponsored enterprise mortgage-back securities and collateralized mortgage obligations	$	948,408	$	—		$	948,408	$	—
	State and municipal debt securities	364,470		—			364,470		—
	U.S. government agency and government-sponsored enterprise securities	326,039		—			326,039		—
	U.S. government securities	20,114		20,114			—		—
	Other securities	5,080		—			5,080		—
	Total securities available for sale	$	1,664,111	$	20,114		$	1,643,997	$	—
	Other assets (Interest rate contracts)	$	9,044	$	—		$	9,044	$	—
	Liabilities
	Other liabilities (Interest rate contracts)	$	9,044	$	—		$	9,044	$	—
	There were no transfers between Level 1 and Level 2 of the valuation hierarchy during the years ended December 31, 2014 and 2013. The Company recognizes transfers between levels of the valuation hierarchy based on the valuation level at the end of the reporting period.
	Nonrecurring Measurements
	Certain assets and liabilities are measured at fair value on a nonrecurring basis after initial recognition such as loans measured for impairment and OREO. The following methods were used to estimate the fair value of each such class of financial instrument:
	Impaired loans—A loan is considered to be impaired when, based on current information and events, it is probable that the Company will be unable to collect all amounts due (both interest and principal) according to the contractual terms of the loan agreement. Impaired loans are measured based on the present value of expected future cash flows discounted at the loan’s effective interest rate, a loan’s observable market price, or the fair market value of the collateral less estimated costs to sell if the loan is a collateral-dependent loan. Generally, the Company utilizes the fair market value of the collateral to measure impairment. The impairment evaluations are performed in conjunction with the ALLL process on a quarterly basis by officers in the Special Credits group, which reports to the Chief Credit Officer. The Real Estate Appraisal Services Department (“REASD”), which also reports to the Chief Credit Officer, is responsible for obtaining appraisals from third-parties or performing internal evaluations. If an appraisal is obtained from a third-party, the REASD reviews the appraisal to evaluate the adequacy of the appraisal report, including its scope, methods, accuracy, and reasonableness.
	Other real estate owned —OREO is real property that the Bank has taken ownership of in partial or full satisfaction of a loan or loans. OREO is generally measured based on the property’s fair market value as indicated by an appraisal or a letter of intent to purchase. OREO is recorded at the lower of the carrying amount or fair value less estimated costs to sell. This amount becomes the property’s new basis. Any write-downs based on the property fair value less estimated costs to sell at the date of acquisition are charged to the allowance for loan and lease losses. Management periodically reviews OREO in an effort to ensure the property is carried at the lower of its new basis or fair value, net of estimated costs to sell. Any write-downs subsequent to acquisition are charged to earnings. The initial and subsequent write-down evaluations are performed by officers in the Special Credits group, which reports to the Chief Credit Officer. The REASD obtains appraisals from third-parties for OREO and performs internal evaluations. If an appraisal is obtained from a third-party, the REASD reviews the appraisal to evaluate the adequacy of the appraisal report, including its scope, methods, accuracy, and reasonableness.
	The following table sets forth the Company’s assets that were measured using fair value estimates on a nonrecurring basis during the years ended December 31, 2014 and 2013:
		Fair value  at		Fair Value Measurements at Reporting Date Using							Losses During the Year Ended
		December 31, 2014		Level 1			Level 2		Level 3		31-Dec-14
		(in thousands)
	OREO	$	5,365	$	—		$	—	$	5,365	$	1,008
		$	5,365	$	—		$	—	$	5,365	$	1,008
		Fair value  at		Fair Value Measurements at Reporting Date Using							Losses During the Year Ended
		December 31, 2013		Level 1			Level 2		Level 3		December 31, 2013
		(in thousands)
	Impaired loans	$	8,973	$	—		$	—	$	8,973	$	1,536
	OREO (1)	5,693		—			—		5,693		1,230
		$	14,666	$	—		$	—	$	14,666	$	2,766
	(1) Reclassified to conform to the current period’s presentation. The reclassification was limited to combining historically reported noncovered OREO and covered OREO into one line item for OREO.
	The losses on impaired loans disclosed above represent the amount of the specific reserve and/or charge-offs during the period applicable to loans held at period end. For 2014, there were no losses recorded during the period to loans still held at period end. The amount of the specific reserve is included in the allowance for loan and lease losses. The losses on OREO disclosed above represent the write-downs taken at foreclosure that were charged to the allowance for loan and lease losses, as well as subsequent write-downs from updated appraisals that were charged to earnings.
	Quantitative information about Level 3 fair value measurements
	The range and weighted-average of the significant unobservable inputs used to fair value our Level 3 nonrecurring assets during 2014 and 2013, along with the valuation techniques used, are shown in the following tables:
		Fair value  at		Valuation Technique		Unobservable Input	Range (Weighted Average) (1)
		December 31, 2014
		(dollars in thousands)
	OREO	$	5,365	Fair Market Value of Collateral		Adjustment to Appraisal Value	N/A (2)
	(1) Discount applied to appraisal value, letter of intent to purchase, or stated value (in the case of accounts receivable and inventory).
(2) Quantitative disclosures are not provided for OREO because there were no adjustments made to the appraisal value during the current period.
	Fair value  at		Valuation Technique		Unobservable Input	Range (Weighted Average) (1)
	December 31, 2013
	(dollars in thousands)
Impaired loans	$	8,973	Fair Market Value of Collateral		Adjustment to Appraisal Value	N/A (2)
OREO (3)	5,693		Fair Market Value of Collateral		Adjustment to Appraisal Value	N/A (2)
(1) Discount applied to appraisal value, letter of intent to purchase, or stated value (in the case of accounts receivable and inventory).
(2) Quantitative disclosures are not provided for impaired loans and OREO because there were no adjustments made to the appraisal value during the current period.
(3) Reclassified to conform to the current period’s presentation. The reclassification was limited to combining historically reported noncovered OREO and covered OREO into one line item for OREO.
Fair value of financial instruments
Because broadly traded markets do not exist for most of the Company’s financial instruments, the fair value calculations attempt to incorporate the effect of current market conditions at a specific time. These determinations are subjective in nature, involve uncertainties and matters of significant judgment and do not include tax ramifications; therefore, the results cannot be determined with precision, substantiated by comparison to independent markets and may not be realized in an actual sale or immediate settlement of the instruments. There may be inherent weaknesses in any calculation technique, and changes in the underlying assumptions used, including discount rates and estimates of future cash flows, could significantly affect the results. For all of these reasons, the aggregation of the fair value calculations presented herein do not represent, and should not be construed to represent, the underlying value of the Company.
The following methods and assumptions were used to estimate the fair value of each class of financial instruments for which it is practicable to estimate that value:
Cash and due from banks and interest-earning deposits with banks—The fair value of financial instruments that are short-term or reprice frequently and that have little or no risk are considered to have a fair value that approximates carrying value (Level 1).
Securities available for sale—Securities at fair value, other than U.S. Treasury Notes, are priced using a combination of market activity, industry recognized information sources, yield curves, discounted cash flow models and other factors (Level 2). U.S. Treasury Notes are priced using quotes in active markets (Level 1).
Federal Home Loan Bank stock—The fair value is based upon the par value of the stock which equates to its carrying value (Level 2).
Loans—Loans are not recorded at fair value on a recurring basis. Nonrecurring fair value adjustments are periodically recorded on impaired loans that are measured for impairment based on the fair value of collateral. For most performing loans, fair value is estimated using expected duration and lending rates that would have been offered on December 31, 2014 or 2013 for loans which mirror the attributes of the loans with similar rate structures and average maturities. The fair values resulting from these calculations are reduced by an amount representing the change in estimated fair value attributable to changes in borrowers’ credit quality since the loans were originated. For nonperforming loans, fair value is estimated by applying a valuation discount based upon loan sales data from the FDIC. For purchased credit impaired loans, fair value is estimated by discounting the expected future cash flows using a lending rate that would have been offered on December 31, 2014 (Level 3).
FDIC loss-sharing asset —The fair value of the FDIC loss-sharing asset is estimated based on discounting the expected future cash flows using an estimated market rate (Level 3).
Interest rate contracts—Interest rate contracts are valued in models, which use readily observable market parameters as their basis (Level 2).
Deposits—For deposits with no contractual maturity, the fair value is equal to the carrying value (Level 1). The fair value of fixed maturity deposits is based on discounted cash flows using the difference between the deposit rate and current market rates for deposits of similar remaining maturities (Level 2).
FHLB advances—The fair value of FHLB advances is estimated based on discounting the future cash flows using the market rate currently offered (Level 2).
Repurchase agreements—The fair value of term repurchase agreements is estimated based on discounting the future cash flows using the market rate currently offered. The carrying amount of sweep repurchase agreements approximates their fair values due to the short period of time between repricing dates (Level 2).
Other Borrowings— Other borrowings are trust preferred obligations assumed by the Company in the Intermountain acquisition. The fair value is estimated as the carrying value as these obligations are redeemable and a market participant would expect redemption in the near-term. Subsequent to year-end, on January 7, 2015, the Company redeemed these trust preferred obligations (Level 2).
Other financial instruments—The majority of our commitments to extend credit and standby letters of credit carry current market interest rates if converted to loans, as such, carrying value is assumed to equal fair value.
The following tables summarize carrying amounts and estimated fair values of selected financial instruments for the periods indicated:
	December 31,
	2014
	Carrying		Fair			Level 1		Level 2		Level 3
	Amount		Value
	(in thousands)
Assets
Cash and due from banks	$	171,221	$	171,221		$	171,221	$	—	$	—
Interest-earning deposits with banks	16,949		16,949			16,949		—		—
Securities available for sale	2,098,257		2,098,257			20,499		2,077,758		—
FHLB stock	33,365		33,365			—		33,365		—
Loans held for sale	1,116		1,116			—		1,116		—
Loans	5,375,809		5,516,286			—		—		5,516,286
FDIC loss-sharing asset	15,174		4,054			—		—		4,054
Interest rate contracts	11,800		11,800			—		11,800		—
Liabilities
Deposits	$	6,924,722	$	6,921,804		$	6,416,017	$	505,787	$	—
FHLB advances	216,568		217,296			—		217,296		—
Repurchase agreements	105,080		106,171			—		106,171		—
Other borrowings	8,248		8,248			—		8,248		—
Interest rate contracts	11,851		11,851			—		11,851		—
	December 31,
	2013
	Carrying		Fair			Level 1		Level 2		Level 3
	Amount		Value
	(in thousands)
Assets
Cash and due from banks	$	165,030	$	165,030		$	165,030	$	—	$	—
Interest-earning deposits with banks	14,531		14,531			14,531		—		—
Securities available for sale	1,664,111		1,664,111			20,114		1,643,997		—
FHLB stock	32,529		32,529			—		32,529		—
Loans held for sale	735		735			—		735		—
Loans	4,444,842		4,605,038			—		—		4,605,038
FDIC loss-sharing asset	39,846		11,248			—		—		11,248
Interest rate contracts	9,044		9,044			—		9,044		—
Liabilities
Deposits	$	5,959,475	$	5,958,747		$	5,449,546	$	509,201	$	—
FHLB advances	36,606		35,080			—		35,080		—
Repurchase agreements	25,000		26,361			—		26,361		—
Interest rate contracts	9,044		9,044			—		9,044		—

Earnings_Per_Common_Share

Earnings Per Common Share	12 Months Ended
	Dec. 31, 2014
Earnings Per Share [Abstract]
Earnings Per Common Share	Earnings per Common Share
	The Company applies the two-class method of computing basic and diluted EPS. Under the two-class method, EPS is determined for each class of common stock and participating security according to dividends declared and participation rights in undistributed earnings. The Company issues restricted shares under share-based compensation plans and preferred shares which qualify as participating securities.
	The following table sets forth the computation of basic and diluted earnings per share for the periods indicated:
			Year Ended December 31,
			2014		2013		2012
			(in thousands except per share)
	Basic EPS:
	Net income		$	81,574	$	60,016	$	46,143
	Less: Earnings allocated to participating securities
	Preferred shares		157		95		—
	Nonvested restricted shares		780		523		443
	Earnings allocated to common shareholders		$	80,637	$	59,398	$	45,700
	Weighted average common shares outstanding		52,618		47,993		39,260
	Basic earnings per common share		$	1.53	$	1.24	$	1.16
	Diluted EPS:
	Earnings allocated to common shareholders (1)		$	80,640	$	59,407	$	45,700
	Weighted average common shares outstanding		52,618		47,993		39,260
	Dilutive effect of equity awards and warrants		565		1,058		3
	Weighted average diluted common shares outstanding		53,183		49,051		39,263
	Diluted earnings per common share		$	1.52	$	1.21	$	1.16
	Potentially dilutive share options that were not included in the computation of diluted EPS because to do so would be anti-dilutive		64		64		9
	__________
	-1	Earnings allocated to common shareholders for basic and diluted EPS may differ under the two-class method as a result of adding common stock equivalents for options and warrants to dilutive shares outstanding, which alters the ratio used to allocate earnings to common shareholders and participating securities for the purposes of calculating diluted EPS.

ShareBased_Payments

Share-Based Payments	12 Months Ended
	Dec. 31, 2014
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Share-Based Payments	Share-Based Payments
	At December 31, 2014, the Company had one equity compensation plan (the “Plan”), which is shareholder approved, that provides for the granting of share options and shares to eligible employees and directors up to 1,800,000 shares.
	Share Awards: Restricted share awards provide for the immediate issuance of shares of Company common stock to the recipient, with such shares held in escrow until certain service conditions are met, generally four years of continual service. Recipients of restricted shares do not pay any cash consideration to the Company for the shares, have the right to vote all shares subject to such grant, and receive all dividends with respect to such shares, whether or not the shares have vested. The fair value of share awards is equal to the fair market value of the Company’s common stock on the date of grant.
	A summary of changes in the Company’s nonvested shares and related information for the years ended December 31, 2014, 2013 and 2012 is presented below:
	Nonvested Shares	Shares		Weighted
				Average
				Grant-Date
				Fair Value
	Nonvested at January 1, 2012	362,675		$	19.24
	Granted	180,841		$	21.32
	Vested	(118,511	)	$	21.65
	Forfeited	(40,915	)	$	18.6
	Nonvested at December 31, 2012	384,090		$	19.54
	Granted	203,441		$	20.78
	Vested	(117,153	)	$	16.9
	Forfeited	(59,780	)	$	20.24
	Nonvested at December 31, 2013	410,598		$	20.79
	Granted	246,068		$	25.97
	Vested	(108,371	)	$	21.45
	Forfeited	(28,510	)	$	21.92
	Nonvested at December 31, 2014	519,785		$	23.03
	As of December 31, 2014, there was $7.0 million of total unrecognized compensation cost related to nonvested share-based compensation arrangements granted under the Plan. That cost is expected to be recognized over a weighted average period of 2.4 years. The total fair value, as measured on the date of vesting, of shares vested during the years ended December 31, 2014, 2013, and 2012 was $2.3 million, $2.5 million, and $2.5 million, respectively.
	Share Options: Option awards are generally granted with an exercise price equal to the market price of the Company’s stock at the date of grant; those option awards generally vest based on three years of continual service and are exercisable for a five-year period after vesting. Option awards granted have a 10-year maximum term.
	The fair value of each option award is estimated on the date of grant using the Black-Scholes option valuation model. The fair value of all options is amortized on a straight-line basis over the requisite service periods, which are generally the vesting periods. The expected life of options granted represents the period of time that they are expected to be outstanding. The expected life is determined based on historical experience with similar awards, giving consideration to the contractual terms and vesting schedules. Expected volatilities of our common stock are estimated at the date of grant based on the historical volatility of the stock. The volatility factor is based on historical stock prices over the most recent period commensurate with the estimated expected life of the award. The risk-free interest rate is based on the U.S. Treasury curve in effect at the time of the award. The expected dividend yield is based on dividend trends and the market value of the Company’s stock price at the time of the award.
	A summary of option activity under the Plan as of December 31, 2014, and changes during the year then ended is presented below.
	Options	Shares		Weighted				Weighted	Aggregate
				Average				Average	Intrinsic
				Exercise				Remaining	Value
				Price				Contractual	$0
								Term
	Balance at December 31, 2013	116,197		$	65.01
	Forfeited	(8,753	)	$	75.32
	Expired	(22,330	)	$	91.95
	Exercised	(9,116	)	$	12.09
	Balance at December 31, 2014	75,998		$	62.41			2.4	$	391
	Vested or expected to vest at December 31, 2014	75,998		$	62.41			2.4	$	391
	Total Exercisable at December 31, 2014	75,998		$	62.41			2.4	$	391
	The total intrinsic value of options exercised during the years ended December 31, 2014, 2013, and 2012 was $138 thousand, $410 thousand, and $5 thousand, respectively. The weighted average grant-date fair value of options granted in during the year ended December 31, 2013 was $3.06. There were no options granted during the years ended December 31, 2014 and 2012. There were no options that vested during the years ended December 2014, 2013, and 2012.
	As of December 31, 2014, outstanding stock options consist of the following:
	Ranges of	Number of		Weighted Average		Weighted Average			Number of		Weighted Average
	Exercise Prices	Option		Remaining		Exercise Price of			Exercisable		Exercise Price of
		Shares		Contractual Life		Option Shares			Option Shares		Exercisable Option
											Shares
	$0.00 - $9.99	21,579		4.3		$	9.91		21,579		$	9.91
	$10.00 - $19.99	600		2.6		$	12.61		600		$	12.61
	$30.00 - $39.99	4,051		2.1		$	30.86		4,051		$	30.86
	$40.00 - $49.99	349		3.5		$	44.49		349		$	44.49
	$50.00 - $136.93	49,419		1.6		$	88.65		49,419		$	88.65
		75,998		2.4		$	62.41		75,998		$	62.41
	It is the Company’s policy to issue new shares for share option exercises and share awards. The Company expenses awards of share options and shares on a straight-line basis over the related vesting term of the award. For the 12 months ended December 31, 2014, 2013 and 2012, the Company recognized pre-tax share-based compensation expense of $2.9 million, $2.8 million and $1.6 million, respectively.

Income_Tax

Income Tax	12 Months Ended
	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Income Tax	Income Tax
	The components of income tax expense (benefit) are as follows:
		Years Ended December 31,
		2014			2013				2012
		(in thousands)
	Current tax expense	$	21,565		$	21,581			$	21,218
	Deferred tax expense (benefit)	14,646			5,413				(3,656		)
	Total	$	36,211		$	26,994			$	17,562
	Significant components of the Company’s deferred tax assets and liabilities are as follows:
		December 31,
		2014			2013 (1)
		(in thousands)
	Deferred tax assets:
	Allowance for loan and lease losses	$	26,341		$	27,196
	Supplemental executive retirement plan	9,037			8,565
	Stock option and restricted stock	1,177			917
	OREO	1,101			7,929
	Nonaccrual interest	68			2,354
	Purchase accounting	15,272			15,551
	Unrealized loss on investment securities	—			7,176
	Net operating losses and credit carryforwards (1)	14,929			1,250
	Other (1)	532			491
	Total deferred tax assets	68,457			71,429
	Deferred tax liabilities:
	Asset purchase tax basis difference	(6,595		)	(7,754		)
	FHLB stock dividends	(4,086		)	(4,159		)
	Deferred loan fees	(4,691		)	(4,512		)
	Unrealized gain on investment securities	(2,987		)	—
	Depreciation	(5,394		)	(7,076		)
	Total deferred tax liabilities	(23,753		)	(23,501		)
	Net deferred tax asset	$	44,704		$	47,928
	__________
	(1) Reclassified to conform to current period presentation. The reclassification was limited to including previously reported amounts for net operating losses and credit carryforwards, which had been included in the row for other deferred tax assets into a separate row.
	A reconciliation of the Company’s effective income tax rate with the federal statutory tax rate is as follows:
		Years Ended December 31,
		2014						2013 (1)						2012 (1)
		Amount			Percent			Amount				Percent		Amount			Percent
		(dollars in thousands)
	Income tax based on statutory rate	$	41,225		35	%		$	30,454			35	%	$	22,297		35	%
	Reduction resulting from:
	Tax exempt instruments	(5,328		)	(5	)%		(4,113		)		(5	)%	(3,906		)	(6	)%
	Life insurance proceeds	(1,352		)	(1	)%		(1,250		)		(1	)%	(1,001		)	(2	)%
	Acquisition costs	448			—	%		1,362				2	%	—			—	%
	Other, net (1)	1,218			2	%		541				—	%	172			—	%
	Income tax provision	$	36,211		31	%		$	26,994			31	%	$	17,562		27	%
	__________
	(1) Reclassified to conform to current period presentation. The reclassification was limited to including previously reported amounts for tax credits in the row for other, net.
	As of December 31, 2014 and 2013, we had no unrecognized tax benefits. There were no amounts related to interest and penalties recognized for the years ended December 31, 2014 and 2013. The tax years subject to examination by federal and state taxing authorities are the years ending December 31, 2014, 2013, 2012 and 2011. As a result of recent acquisitions, the Company has net operating loss carryforwards in the federal, Idaho and Oregon jurisdictions of of $30.7 million, $38.1 million and $13.5 million , respectively, which begin to expire in 2024 and federal and Oregon credit carryforwards of $561 thousand and $1.6 million, respectively. Federal credit carryforwards related to alternative minimum taxes, and have no expiration, while the Oregon credit carryforwards begin to expire in 2015. The amount of carryforwards that may be utilized annually is limited under Sections 382 and 383 as a result of changes in control. Management believes that these carryforwards will be used in the normal course of business, and as such, has not recorded a valuation allowance.

Regulatory_Capital_Requirement

Regulatory Capital Requirements	12 Months Ended
	Dec. 31, 2014
Regulatory Capital Requirements [Abstract]
Regulatory Capital Requirements	Regulatory Capital Requirements
	The Company (on a consolidated basis) and its banking subsidiary are subject to various regulatory capital requirements administered by the federal banking agencies. Failure to meet minimum capital requirements can initiate certain mandatory and possibly additional discretionary actions by regulators that, if undertaken, could have a direct material effect on the Company and its banking subsidiary’s financial statements. Under capital adequacy guidelines and the regulatory framework for prompt corrective action, the Company and its banking subsidiary must meet specific capital guidelines that involve quantitative measures of assets, liabilities, and certain off-balance sheet items as calculated under regulatory accounting practices. The capital amounts and classification are also subject to qualitative judgments by the regulators about components, risk weightings, and other factors. Prompt corrective action provisions are not applicable to bank holding companies.
	Quantitative measures established by regulation to ensure capital adequacy require the Company and its banking subsidiary to maintain minimum amounts and ratios (set forth in the following table) of total and Tier 1 capital to risk-weighted assets (as defined in the regulations) and of Tier 1 capital to average assets (as defined in the regulations). Management believes, as of December 31, 2014 and 2013, that the Company and Columbia Bank met all capital adequacy requirements to which they are subject.
	As of December 31, 2014, the most recent notification from the Federal Deposit Insurance Corporation categorized Columbia Bank as well capitalized under the regulatory framework for prompt corrective action. To be categorized as well capitalized, an institution must maintain minimum total risk-based, Tier 1 risk-based, and Tier 1 leverage ratios as set forth in the following tables. There are no conditions or events since the notification that management believes have changed Columbia Bank’s category. The Company and its banking subsidiary’s actual capital amounts and ratios as of December 31, 2014 and 2013, are also presented in the following table.
		Actual				For Capital				To Be Well
						Adequacy				Capitalized Under
						Purposes				Prompt
										Corrective Action
										Provision
		Amount		Ratio		Amount		Ratio		Amount		Ratio
		(dollars in thousands)
	As of December 31, 2014
	Total Capital (to risk-weighted assets):
	The Company	$	890,029	14.13	%	$	503,989	8	%	N/A		N/A
	Columbia Bank	$	860,755	13.67	%	$	503,852	8	%	$	629,816	10	%
	Tier 1 Capital (to risk-weighted assets):
	The Company	$	817,805	12.98	%	$	251,995	4	%	N/A		N/A
	Columbia Bank	$	788,531	12.52	%	$	251,926	4	%	$	377,889	6	%
	Tier 1 Capital (to average assets):
	The Company	$	817,805	10.57	%	$	309,579	4	%	N/A		N/A
	Columbia Bank	$	788,531	9.79	%	$	322,029	4	%	$	402,537	5	%
	As of December 31, 2013
	Total Capital (to risk-weighted assets):
	The Company	$	760,349	14.68	%	$	414,300	8	%	N/A		N/A
	Columbia Bank	$	700,099	13.52	%	$	414,238	8	%	$	517,797	10	%
	Tier 1 Capital (to risk-weighted assets):
	The Company	$	695,489	13.43	%	$	207,150	4	%	N/A		N/A
	Columbia Bank	$	635,248	12.27	%	$	207,119	4	%	$	310,678	6	%
	Tier 1 Capital (to average assets):
	The Company	$	695,489	10.19	%	$	272,891	4	%	N/A		N/A
	Columbia Bank	$	635,248	9.29	%	$	273,560	4	%	$	341,950	5	%

Branch_Sales

Branch Sales	12 Months Ended
	Dec. 31, 2014
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Disposal Groups, Including Discontinued Operations, Disclosure [Text Block]	Branch Sales
	On August 23, 2014, Columbia completed a branch sale transaction to Sound Community Bank. In the transaction, Columbia sold three branches and related assets and deposit liabilities to Sound Community Bank. The transaction was completed with a transfer of $22.2 million in deposits to Sound Community Bancorp in exchange for a deposit premium of 2.35%. Also included in the branch sale were $1.1 million in loans and $3.8 million in premises and equipment. The Company recognized a gain of $565 thousand related to the deposit premium, which was recorded in the line item Other noninterest income in the consolidated statements of income. In addition, the Company recorded a $50 thousand loss on the disposal of premises and equipment related to this transaction, which was recorded in the line item Other noninterest expense in the consolidated statements of income.

Parent_Company_Financial_Infor

Parent Company Financial Information	12 Months Ended
	Dec. 31, 2014
Condensed Financial Information of Parent Company Only Disclosure [Abstract]
Parent Company Financial Information	Parent Company Financial Information
	Condensed Statements of Income—Parent Company Only
		Years Ended December 31,
		2014			2013			2012
		(in thousands)
	Income
	Dividend from banking subsidiary	$	16,200		$	183,000		$	48,950
	Interest-earning deposits	25			68			153
	Other income	10			7			—
	Total income	16,235			183,075			49,103
	Expense
	Compensation and employee benefits	530			658			182
	Other borrowings	83			258			—
	Other expense	1,433			4,162			1,193
	Total expenses	2,046			5,078			1,375
	Income before income tax benefit and equity in undistributed net income (loss) of subsidiaries	14,189			177,997			47,728
	Income tax benefit	(704		)	(1,552		)	(435		)
	Income before equity in undistributed net income of subsidiaries	14,893			179,549			48,163
	Equity in undistributed net income (loss) of subsidiaries	66,681			(119,533		)	(2,020		)
	Net income	$	81,574		$	60,016		$	46,143
	Condensed Balance Sheets—Parent Company Only
		December 31,
		2014			2013
		(in thousands)
	Assets
	Cash and due from banking subsidiary	$	10,322		$	3,006
	Interest-earning deposits	12,274			50,678
	Total cash and cash equivalents	22,596			53,684
	Investment in banking subsidiary	1,207,143			993,002
	Investment in other subsidiaries	5,351			5,037
	Other assets	5,273			1,952
	Total assets	$	1,240,363		$	1,053,675
	Liabilities and Shareholders’ Equity
	Other borrowings	$	8,248		$	—
	Other liabilities	3,940			426
	Total liabilities	12,188			426
	Shareholders’ equity	1,228,175			1,053,249
	Total liabilities and shareholders’ equity	$	1,240,363		$	1,053,675
	Condensed Statements of Cash Flows—Parent Company Only
		Years Ended December 31,
		2014			2013			2012
		(in thousands)
	Operating Activities
	Net income	$	81,574		$	60,016		$	46,143
	Adjustments to reconcile net income to net cash provided by operating activities:
	Equity in undistributed net loss (income) of subsidiaries	(66,681		)	119,533			2,020
	Stock-based compensation expense	2,859			2,844			1,622
	Net changes in other assets and liabilities	(403		)	6,830			(264		)
	Net cash provided by operating activities	17,349			189,223			49,521
	Investing Activities
	Net cash acquired (paid) in business combinations	10,277			(53,159		)	—
	Net cash provided by (used in) investing activities	10,277			(53,159		)	—
	Financing Activities
	Preferred stock dividends	(96		)	(32		)	—
	Common stock dividends	(49,494		)	(19,858		)	(38,824		)
	Repayment of other borrowings	(14,636		)	(51,000		)	—
	Exercise of warrants	5,000			—			—
	Purchase and retirement of common stock	(622		)	(429		)	—
	Proceeds from exercise of stock options	929			1,092			713
	Downstream stock offering proceeds to the Bank	—			(100,000		)	—
	Excess tax benefit associated with share-based compensation	205			1,203			—
	Net cash used in financing activities	(58,714		)	(169,024		)	(38,111		)
	Increase (decrease) in cash and cash equivalents	(31,088		)	(32,960		)	11,410
	Cash and cash equivalents at beginning of year	53,684			86,644			75,234
Cash and cash equivalents at end of year	$	22,596		$	53,684		$	86,644

Summary_Of_Quarterly_Financial

Summary Of Quarterly Financial Information (Unaudited)	12 Months Ended
	Dec. 31, 2014
Quarterly Financial Information Disclosure [Abstract]
Summary of Quarterly Financial Information (Unaudited)	Summary of Quarterly Financial Information (Unaudited)
	Quarterly financial information for the years ended December 31, 2014 and 2013 is summarized as follows:
		First			Second		Third		Fourth			Year Ended
		Quarter			Quarter		Quarter		Quarter			December 31,
		(in thousands, except per share amounts)
	2014
	Total interest income	$	74,925		$	76,087	$	77,133	$	79,897		$	308,042
	Total interest expense	985			963		913		1,133			3,994
	Net interest income	73,940			75,124		76,220		78,764			304,048
	Provision for loan and lease losses	1,922			2,117		980		1,708			6,727
	Noninterest income	14,008			14,627		15,930		15,185			59,750
	Noninterest expense	57,386			57,764		59,982		64,154			239,286
	Income before income taxes	28,640			29,870		31,188		28,087			117,785
	Provision for income taxes	8,796			8,643		9,605		9,167			36,211
	Net income	$	19,844		$	21,227	$	21,583	$	18,920		$	81,574
	Per common share (1)
	Earnings (basic)	$	0.38		$	0.4	$	0.41	$	0.34		$	1.53
	Earnings (diluted)	$	0.37		$	0.4	$	0.41	$	0.34		$	1.52
	2013
	Total interest income	$	54,761		$	82,268	$	81,599	$	78,307		$	296,935
	Total interest expense	1,279			2,279		1,184		1,098			5,840
	Net interest income	53,482			79,989		80,415		77,209			291,095
	Provision (recapture) for loan and lease losses	(20		)	288		3,313		(3,682		)	(101		)
	Noninterest income	1,658			6,808		7,622		10,612			26,700
	Noninterest expense	38,049			64,504		64,714		63,619			230,886
	Income before income taxes	17,111			22,005		20,010		27,884			87,010
	Provision for income taxes	4,935			7,414		6,734		7,911			26,994
	Net income	$	12,176		$	14,591	$	13,276	$	19,973		$	60,016
	Per common share (1)
	Earnings (basic)	$	0.31		$	0.28	$	0.26	$	0.39		$	1.24
	Earnings (diluted)	$	0.31		$	0.28	$	0.25	$	0.38		$	1.21
	__________
	(1) Due to averaging of shares, quarterly earnings per share may not add up to the totals reported for the full year.

Summary_of_Significant_Account1

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2014
Accounting Policies [Line Items]
Cash and cash equivalents	Cash and cash equivalents
	Cash and cash equivalents include cash and due from banks, and interest bearing balances due from correspondent banks and the Federal Reserve Bank. Cash and cash equivalents have a maturity of 90 days or less at the time of purchase.
Securities	Securities
	Securities are classified based on management’s intention on the date of purchase. All securities are classified as available for sale and are presented at fair value. Unrealized gains or losses on securities available for sale are excluded from net income but are included as separate components of other comprehensive income, net of taxes. Purchase premiums or discounts on securities available for sale are amortized or accreted into income using the interest method over the terms of the individual securities. The Company performs a quarterly assessment to determine whether a decline in fair value below amortized cost is other-than-temporary. Amortized cost includes adjustments made to the cost of an investment for accretion, amortization, collection of cash and previous other-than temporary impairment recognized in earnings. Other-than-temporary impairment exists when it is probable that the Company will be unable to recover the entire amortized cost basis of the security.
	In performing the quarterly assessment for debt securities, management considers whether or not the Company expects to recover the entire amortized cost basis of the security. In addition, management also considers whether it is more likely than not that it will not have to sell the security before recovery of its cost basis. If the Company intends to sell a security or it is more likely than not it will be required to sell a security prior to recovery of its cost basis, the entire amount of impairment is recognized in earnings. If the Company does not intend to sell the security or it is not more likely than not it will be required to sell the security prior to recovery of its cost basis, the credit loss component of impairment is recognized in earnings and impairment associated with non-credit factors, such as market liquidity, is recognized in other comprehensive income net of tax. A credit loss is the difference between the cost basis of the security and the present value of cash flows expected to be collected, discounted at the security’s effective interest rate at the date of acquisition. The cost basis of an other-than-temporarily impaired security is written down by the amount of impairment recognized in earnings. The new cost basis is not adjusted for subsequent recoveries in fair value. However, the difference between the new amortized cost basis and the cash flows expected to be collected is accreted as interest income. The total other-than-temporary impairment, if any, is presented in the consolidated statements of income with a reduction for the amount of other-than-temporary impairment that is recognized in other comprehensive income, if any.
	Realized gains or losses on sales of securities available for sale are recorded using the specific identification method.
Federal Home Loan Bank Stock	Federal Home Loan Bank Stock
	The Company’s investment in Federal Home Loan Bank (“FHLB”) stock is carried at par value because the shares can only be redeemed with the FHLB at par. The Company is required to maintain a minimum level of investment in FHLB stock based on specific percentages of its outstanding mortgages and FHLB advances. Stock redemptions are at the discretion of the FHLB or of the Company, upon five years’ prior notice for FHLB Class B stock or six months notice for FHLB Class A stock to the FHLB. FHLB stock is subject to recoverability testing per the Financial Services—Depository and Lending topic of the FASB Accounting Standards Codification (“ASC”).
Loans	Loans, excluding purchased credit impaired loans are generally carried at the unpaid principal balance, net of premiums, unearned discounts and net deferred loan fees. Net deferred loan fees include deferred unamortized fees less direct incremental loan origination costs. Net deferred loan fees, premiums and unearned discounts are amortized into interest income using either the interest method or straight-line method over the terms of the loans, adjusted for actual prepayments. The amortization is calculated using the interest method for all loans except revolving loans, for which the straight-line method is used. Interest income is accrued as earned. Fees related to lending activities other than the origination or purchase of loans are recognized as noninterest income during the period the related services are performed.
	Nonaccrual loans—Loans are placed on nonaccrual status when a loan becomes contractually past due 90 days with respect to interest or principal unless the loan is both well secured and in the process of collection, or if full collection of interest or principal becomes uncertain. When a loan is placed on nonaccrual status, any accrued and unpaid interest receivable is reversed and the recognition of net deferred loan fees, premiums and unearned discounts ceases. Thereafter, interest collected on the loan is accounted for on the cash collection or cost recovery method until qualifying for return to accrual status. Generally, a loan may be returned to accrual status when the delinquent principal and interest are brought current in accordance with the terms of the loan agreement for a minimum period of six months and future payments are reasonably assured.
	Impaired loans—Loans are considered impaired when based on current information and events, it is probable that the Company will be unable to collect all amounts due according to the contractual terms of the loan agreement or when a loan has been modified in a troubled debt restructuring. The assessment for impairment occurs when and while such loans are designated as classified per the Company’s internal risk rating system or when and while such loans are on nonaccrual. All nonaccrual loans greater than $500,000 and all troubled debt restructured loans are considered impaired and analyzed individually on a quarterly basis. Classified loans with an outstanding balance greater than $500,000 are evaluated for potential impairment on a quarterly basis.
	When a loan with unique risk characteristics has been identified as being impaired, the amount of impairment will be measured by the Company using discounted cash flows, except when it is determined that the remaining source of repayment for the loan is the operation or liquidation of the underlying collateral. In these cases, the current fair value of the collateral, reduced by costs to sell, will be used in place of discounted cash flows. As a final alternative, the observable market price of the debt may be used to assess impairment. Predominantly, the Company uses the fair value of collateral approach based upon a reliable valuation.
	When the measurement of the impaired loan is less than the recorded amount of the loan, an impairment is recognized by recording a charge-off to the allowance for loan and lease losses or by designating a specific reserve. The Company’s policy is to record cash receipts received on impaired loans first as reductions to principal and then to interest income.
	Restructured Loans—A loan is classified as a troubled debt restructuring when a borrower is experiencing financial difficulties that lead to a restructuring of the loan, and the Company grants concessions to the borrower in the restructuring that it would not otherwise consider. These concessions may include interest rate reductions, principal forgiveness, extension of maturity date and other actions intended to minimize potential losses. Generally, a nonaccrual loan that is restructured remains on nonaccrual status for a period of six months to demonstrate that the borrower can meet the restructured terms. If the borrower’s performance under the new terms is not reasonably assured, the loan remains classified as a nonaccrual loan.
	Purchased Credit Impaired Loans (“PCI Loans”)—Loans acquired with evidence of credit deterioration since origination for which it is probable that all contractually required payments will not be collected are accounted for under ASC 310-30, Loans and Debt Securities Acquired with Deteriorated Credit Quality, formerly SOP 03-3 Accounting for Certain Loans or Debt Securities Acquired in a Transfer. In addition, because of the significant discounts associated with certain of the acquired loan portfolios, the Company elected to account for those certain acquired loans under ASC 310-30.
	In situations where such loans have similar risk characteristics, loans are aggregated into pools to estimate cash flows. A pool is accounted for as a single asset with a single interest rate, cumulative loss rate and cash flow expectation. Expected cash flows at the acquisition date in excess of the fair value of loans are considered to be accretable yield, which is recognized as interest income over the life of the loan pool using a level yield method if the timing and amount of the future cash flows of the pool is reasonably estimable. Subsequent to the acquisition date, any increases in cash flow over those expected at purchase date in excess of fair value are recorded as interest income prospectively. Any subsequent decreases in cash flow over those expected at purchase date due to credit deterioration are recognized by recording an allowance for losses on purchased credit impaired loans. Any disposals of loans, including sales of loans, payments in full or foreclosures result in the removal of the loan from the loan pool at the carrying amount.
	Unfunded loan commitments—Unfunded commitments are generally related to providing credit facilities to clients of the Bank and are not actively traded financial instruments. These unfunded commitments are disclosed as financial instruments with off-balance sheet risk in Note 17 in the Notes to Consolidated Financial Statements.
Allowance for Loan and Lease Losses	Allowance for Loan and Lease Losses
	The Company accounts for the credit risk associated with lending activities through its allowance for loan and lease losses and provision for loan and lease losses. The provision is the expense recognized in the consolidated statements of income to adjust the allowance to the levels deemed appropriate by management, as determined through application of the Company’s allowance methodology procedures. The provision for loan and lease losses reflects management’s judgment of the adequacy of the allowance for loan and lease losses. Loan and lease losses are charged against the allowance when management believes the collectability of a loan balance is unlikely. Subsequent recoveries, if any, are credited to the allowance.
	The allowance for loan and lease losses is evaluated on a regular basis by management and is based upon management’s periodic review of the collectability of the loans in light of historical experience, the nature and volume of the loan portfolio, adverse situations that may affect the borrower’s ability to repay, and estimated value of any underlying collateral and prevailing economic conditions. This evaluation is inherently subjective as it requires estimates that are susceptible to significant revision as more information becomes available.
	The allowance consists of general, specific, and unallocated components. The general component covers loans not specifically measured for impairment and is based on historical loss experience adjusted for qualitative factors. The specific component relates to loans that are impaired. For impaired loans an allowance is established when the discounted cash flows (or collateral value or observable market price) of the impaired loan is lower than the carrying value of that loan. The unallocated allowance provides for other credit losses inherent in the Company’s loan portfolio that may not have been contemplated in the general and specific components of the allowance. This unallocated amount generally comprises less than 5% of the allowance. The unallocated amount is reviewed periodically based on trends in credit losses, the results of credit reviews and overall economic trends.
Allowance for Unfunded Commitments and Letters of Credit	Allowance for Unfunded Commitments and Letters of Credit
	The allowance for unfunded commitments is maintained at a level believed by management to be sufficient to absorb estimated probable losses related to these unfunded credit facilities. The determination of the adequacy of the allowance is based on periodic evaluations of the unfunded credit facilities including an assessment of the probability of commitment usage, credit risk factors for loans outstanding to these same customers, and the terms and expiration dates of the unfunded credit facilities. The allowance for unfunded commitments is included in other liabilities on the consolidated balance sheets, with changes to the balance charged against noninterest expense.
Premises and Equipment	Premises and Equipment
	Land, buildings, leasehold improvements and equipment are stated at cost less accumulated depreciation and amortization. Gains or losses on dispositions are reflected in current operations. Expenditures for improvements and major renewals are capitalized, and ordinary maintenance, repairs and small purchases are charged to operating expenses. Depreciation and amortization are computed based on the straight-line method over the estimated useful lives of the various classes of assets. The ranges of useful lives for the principal classes of assets are as follows:
	Buildings and building improvements	5 to 39 years
	Leasehold improvements	Term of lease or useful life, whichever is shorter
	Furniture, fixtures and equipment	3 to 7 years
	Vehicles	5 years
	Computer software	3 to 5 years
Software	Software
	Capitalized software is stated at cost, less accumulated amortization. Amortization is computed on a straight-line basis and charged to expense over the estimated useful life of the software which is generally three years. Capitalized software is included in Premises and equipment, net in the consolidated balance sheets.
Other Real Estate Owned—Noncovered	Other Real Estate Owned
	OREO is composed of real estate acquired in satisfaction of loans. Properties acquired by foreclosure or deed in lieu of foreclosure are transferred to OREO and are recorded at fair value less estimated costs to sell, at the date of transfer of the property. If the carrying value exceeds the fair value at the time of the transfer, the difference is charged to the allowance for loan and lease losses. The fair value of the OREO property is based upon current appraisal. Losses that result from the ongoing periodic valuation of these properties are charged to the net cost of operation of OREO in the period in which they are identified. Improvements to the OREO are capitalized and holding costs are charged to the net cost of operation of OREO as incurred.
Covered Assets and Related FDIC Loss Sharing Asset	FDIC Loss-sharing Asset
	The acquisition date fair value of the reimbursement the Company expected to receive from the FDIC under loss-sharing agreements was recorded in the FDIC loss-sharing asset on the consolidated balance sheet. Subsequent to initial recognition, the FDIC loss-sharing asset is reviewed quarterly and adjusted for any changes in expected cash flows. These adjustments are measured on the same basis as the related covered assets. Any decrease in expected cash flows for the covered assets due to an increase in expected credit losses will increase the FDIC loss-sharing asset and any increase in expected future cash flows for the covered assets due to a decrease in expected credit losses will decrease the FDIC loss-sharing asset. Changes in the estimated cash flows on covered assets that are immediately recognized in income generally result in a similar immediate adjustment to the loss-sharing asset while changes in expected cash flows on covered assets that are accounted for as an adjustment to yield generally result in adjustments to the amortization or accretion rate for the loss-sharing asset. Increases and decreases to the FDIC loss-sharing asset are recorded as adjustments to noninterest income.
Goodwill and Intangibles	Goodwill and Intangibles
	Net assets of companies acquired in purchase transactions are recorded at fair value at the date of acquisition. Identified intangibles are amortized on an accelerated basis over the period benefited. Goodwill is not amortized but is reviewed for potential impairment during the third quarter on an annual basis or, more frequently, if events or circumstances indicate a potential impairment, at the reporting unit level. A reporting unit is an operating segment or one level below an operating segment for which discrete financial information is available and regularly reviewed by management. The Company consists of a single reporting unit. If the fair value of the reporting unit, including goodwill, is determined to be less than the carrying amount of the reporting unit, a further test is required to measure the amount of impairment. If an impairment loss exists, the carrying amount of goodwill is adjusted to a new cost basis. Subsequent reversal of a previously recognized goodwill impairment loss is prohibited.
	Intangible assets are evaluated for impairment if events and circumstances indicate a possible impairment. Such evaluation of other intangible assets is based on undiscounted cash flow projections. At December 31, 2014, intangible assets included on the consolidated balance sheets principally consists of a core deposit intangible amortized using an accelerated method with an original estimated life 10 years.
Income Taxes	Income Taxes
	The provision for income taxes includes current and deferred income tax expense on net income adjusted for permanent and temporary differences such as interest income on state and municipal securities and affordable housing credits. Deferred tax assets and liabilities are recognized for the expected future tax consequences of existing temporary differences between the financial reporting and tax reporting basis of assets and liabilities using enacted tax laws and rates. The effect on deferred tax assets and liabilities of a change in tax rates is recognized in income in the period that includes the enactment date. On a quarterly basis, management evaluates deferred tax assets to determine if these tax benefits are expected to be realized in future periods. This determination is based on facts and circumstances, including the Company’s current and future tax outlook. To the extent a deferred tax asset is no longer considered “more likely than not” to be realized, a valuation allowance is established.
Earnings per Common Share	Earnings per Common Share
	The Company’s capital structure includes convertible preferred shares, common shares, restricted common shares, common share options, and during portions of 2014 and 2013, warrants to purchase common shares. Restricted common shares participate in dividends declared on common shares at the same rate as common shares. Preferred shares participate in dividends declared on common shares on an “as if converted” basis. Accordingly, the Company calculates earnings per common share (“EPS”) using the two-class method under the Earnings per Share topic of the FASB ASC. The two-class method is an earnings allocation formula that treats a participating security as having rights to earnings that otherwise would have been available to common shareholders but does not require the presentation of basic and diluted EPS for securities other than common shares.
	Under the two-class method, basic EPS is computed by dividing earnings allocated to common shareholders by the weighted average number of common shares outstanding for the period. Earnings allocated to common shareholders represents net income reduced by earnings allocated to participating securities. Participating securities include nonvested restricted stock awards and preferred stock. Diluted EPS is computed in the same manner as basic earnings per share except that the denominator is increased to include the number of additional common shares that would have been outstanding if certain shares issuable upon exercise of options and warrants were included unless those additional shares would have been anti-dilutive. For the diluted EPS computation, the treasury stock method is applied and compared to the two-class method and whichever method results in a more dilutive impact is utilized to calculate diluted EPS.
Advertising	Advertising
	Advertising costs are generally expensed as incurred.
Share-Based Payment	Share-Based Payment
	The Company accounts for stock options and stock awards in accordance with the Compensation—Stock Compensation topic of the FASB ASC. Authoritative guidance requires the Company to measure the cost of employee services received in exchange for an award of equity instruments, such as stock options or stock awards, based on the fair value of the award on the grant date. This cost must be recognized in the consolidated statements of income over the vesting period of the award.
	The Company issues restricted stock awards which generally vest over a four- or five-year period during which time the holder receives dividends and has full voting rights. Restricted stock is valued at the closing price of the Company’s stock on the date of an award.
Derivatives and Hedging Activities	Derivatives and Hedging Activities
	In accordance with the Derivatives and Hedging topic of the FASB ASC, the Company recognizes derivatives as assets or liabilities on the consolidated balance sheets at their fair value. The Company periodically enters into interest rate contracts with customers and offsetting contracts with third parties. As these interest rate contracts are not designated as hedges under the Derivatives and Hedging topic of the FASB ASC, the changes in fair value of these instruments are recognized immediately in earnings.
Purchased Credit Impaired Loans [Member]
Accounting Policies [Line Items]
Allowance for Loan and Lease Losses	Allowance for Loan Losses on Purchased Credit Impaired Loans
	The Company updates its cash flow projections for purchased credit impaired loans accounted for under ASC 310-30 on a quarterly basis. Assumptions utilized in this process include projections related to probability of default, loss severity, prepayment and recovery lag. Projections related to probability of default and prepayment are calculated utilizing a loan migration analysis. The loan migration analysis is a matrix of probability that is used to estimate the probability of a loan pool transitioning into a particular delinquency state given its delinquency state at the remeasurement date. Loss severity factors are based upon either actual charge-off data within the loan pools or industry averages and recovery lags are based upon the collateral within the loan pools.
	Any decreases in expected cash flows after the acquisition date and subsequent measurement periods are recognized by recording a provision for loan losses. See Purchased Credit Impaired Loans for further discussion.

Business_Combinations_Tables

Business Combinations (Tables)	12 Months Ended
	Dec. 31, 2014
Intermountain Community Bancorp [Member]
Business Acquisition [Line Items]
Schedule of Recognized Identified Assets Acquired and Liabilities Assumed [Table Text Block]	The table below summarizes the amounts recognized as of the acquisition date for each major class of assets acquired and liabilities assumed:
		November 1, 2014
		(in thousands)
	Purchase price as of November 1, 2014	$	131,935
	Recognized amounts of identifiable assets acquired and (liabilities assumed), at fair value:
	Cash and cash equivalents	$	47,283
	Investment securities	299,458
	Federal Home Loan Bank stock	2,124
	Acquired loans	502,595
	Interest receivable	4,656
	Premises and equipment	20,696
	Other real estate owned	2,752
	Core deposit intangible	10,900
	Other assets	35,353
	Deposits	(736,795		)
	Other borrowings	(22,904		)
	Securities sold under agreements to repurchase	(59,043		)
	Other liabilities	(13,725		)
	Total fair value of identifiable net assets	93,350
	Goodwill	$	38,585
Business Acquisition, Pro Forma Information [Table Text Block]	The following table presents certain unaudited pro forma information for illustrative purposes only, for the years ended December 31, 2014 and 2013 as if Intermountain had been acquired on January 1, 2013. This unaudited estimated pro forma financial information combines the historical results of Intermountain with the Company’s consolidated historical results and includes certain adjustments reflecting the estimated impact of certain fair value adjustments for the respective periods. The pro forma information is not indicative of what would have occurred had the acquisition occurred on January 1, 2013. In particular, no adjustments have been made to eliminate the impact of other-than-temporary impairment losses and losses recognized on the sale of securities that may not have been necessary had the investment securities been recorded at fair value as of January 1, 2013. The unaudited pro forma information does not consider any changes to the provision for credit losses resulting from recording loan assets at fair value. Additionally, Columbia expects to achieve further operating cost savings and other business synergies, including revenue growth, as a result of the acquisition which are not reflected in the pro forma amounts that follow. As a result, actual amounts would have differed from the unaudited pro forma information presented.
		Unaudited Pro Forma
		Years Ended December 31,
		2014			2013
		(in thousands except per share)
	Total revenues (net interest income plus noninterest income)	$	397,152		$	360,655
	Net income	$	85,939		$	72,587
	Earnings per share - basic	$	1.56		$	1.32
	Earnings per share - diluted	$	1.55		$	1.31
Business Acquisition, Integration, Restructuring and Other Related Costs [Text Block]	The following table shows the impact of the acquisition-related expenses related to the acquisition of Intermountain for the periods indicated to the various components of noninterest expense:
		Year ended December 31,
		2014
		(in thousands)
	Noninterest Expense
	Compensation and employee benefits	$	2,077
	Occupancy	44
	Advertising and promotion	464
	Data processing and communications	—
	Legal and professional fees	2,114
	Other	197
	Total impact of acquisition-related costs to noninterest expense	$	4,896
West Coast Bancorp [Member]
Business Acquisition [Line Items]
Business Acquisition, Pro Forma Information [Table Text Block]	The following table presents certain unaudited pro forma information for illustrative purposes only, for the years ended December 31, 2013 and 2012 as if West Coast had been acquired on January 1, 2012. The unaudited estimated pro forma information combines the historical results of West Coast with the Company’s consolidated historical results and includes certain adjustments reflecting the estimated impact of certain fair value adjustments for the respective periods. The pro forma information is not indicative of what would have occurred had the acquisition occurred on January 1, 2012. In particular, no adjustments have been made to eliminate the impact of other-than-temporary impairment losses and losses recognized on the sale of securities that may not have been necessary had the investment securities been recorded at fair value on January 1, 2012. The unaudited pro forma information does not consider any changes to the provision for credit losses resulting from recording loan assets at fair value. Additionally, Columbia expects to achieve further operating cost savings and other business synergies, including revenue growth, as a result of the acquisition which are not reflected in the pro forma amounts that follow. As a result, actual amounts would have differed from the unaudited pro forma information presented.
		Unaudited Pro Forma
		Years Ended December 31,
		2013			2012
		(in thousands except per share)
	Total revenues (net interest income plus noninterest income)	$	337,712		$	420,167
	Net income	$	76,496		$	91,261
	Earnings per share - basic	$	1.5		$	1.79
	Earnings per share - diluted	$	1.46		$	1.74
Business Acquisition, Integration, Restructuring and Other Related Costs [Text Block]	The following table shows the impact of the acquisition-related expenses related to the acquisition of West Coast for the periods indicated to the various components of noninterest expense:
		Years ended December 31,
		2014			2013		2012
		(in thousands)
	Noninterest Expense
	Compensation and employee benefits	$	798		$	8,440	$	—
	Occupancy	696			4,684		—
	Advertising and promotion	—			877		2
	Data processing and communications	684			767		—
	Legal and professional fees	383			4,766		1,760
	Other	1,975			5,954		18
	Total impact of acquisition-related costs to noninterest expense	$	4,536		$	25,488	$	1,780

Securities_Tables

Securities (Tables)	12 Months Ended
	Dec. 31, 2014
Available-for-sale Securities [Abstract]
Securities Available for Sale	The following table summarizes the amortized cost, gross unrealized gains and losses and the resulting fair value of securities available for sale:
		Amortized			Gross			Gross			Fair Value
		Cost			Unrealized			Unrealized
					Gains			Losses
	December 31, 2014	(in thousands)
	U.S. government agency and government-sponsored enterprise mortgage-backed securities and collateralized mortgage obligations	$	1,160,378		$	10,219		$	(8,210	)	$	1,162,387
	State and municipal securities	483,578			14,432			(1,526		)	496,484
	U.S. government agency and government-sponsored enterprise securities	416,919			856			(4,069		)	413,706
	U.S. government securities	20,910			—			(411		)	20,499
	Other securities	5,284			20			(123		)	5,181
	Total	$	2,087,069		$	25,527		$	(14,339	)	$	2,098,257
	December 31, 2013
	U.S. government agency and government-sponsored enterprise mortgage-backed securities and collateralized mortgage obligations	$	961,442		$	10,640		$	(23,674	)	$	948,408
	State and municipal securities	357,013			11,450			(3,993		)	364,470
	U.S. government agency and government-sponsored enterprise securities	335,671			434			(10,066		)	326,039
	U.S. government securities	21,081			—			(967		)	20,114
	Other securities	5,284			27			(231		)	5,080
	Total	$	1,680,491		$	22,551		$	(38,931	)	$	1,664,111
Schedule of gross realized gains and losses on sales and calls of securities available for sale [Table Text Block]	The following table provides the gross realized gains and losses on the sales and calls of securities for the periods indicated:
		Years Ended December 31,
		2014			2013			2012
		(in thousands)
	Gross realized gains	$	553		$	632		$	4,447
	Gross realized losses	(1		)	(170		)	(714		)
	Net realized gains	$	552		$	462		$	3,733
Schedule of Contractual Maturities of Investment Securities Available for Sale	The scheduled contractual maturities of investment securities available for sale at December 31, 2014 are presented as follows:
		December 31, 2014
		Amortized Cost			Fair Value
		(in thousands)
	Due within one year	$	18,872		$	19,028
	Due after one year through five years	426,532			426,035
	Due after five years through ten years	534,515			537,175
	Due after ten years	1,101,866			1,110,838
	Other securities with no stated maturity	5,284			5,181
	Total investment securities available-for-sale	$	2,087,069		$	2,098,257
Schedule of Securities pledged as collateral [Table Text Block]	The following table summarizes the carrying value of securities pledged as collateral to secure public deposits, borrowings and other purposes as permitted or required by law:
		December 31, 2014			December 31, 2013
		(in thousands)
	Washington and Oregon State to secure public deposits	$	328,400		$	277,012
	Federal Reserve Bank to secure borrowings	41,146			42,694
	Other securities pledged	157,097			43,081
	Total securities pledged as collateral	$	526,643		$	362,787
Summary of Gross Unrealized Losses and Fair Value of the Investments with Unrealized Losses	The following tables show the gross unrealized losses and fair value of the Company’s investments with unrealized losses that are not deemed to be other-than-temporarily impaired, aggregated by investment category and length of time that individual securities have been in a continuous unrealized loss position at December 31, 2014 and 2013:
		Less than 12 Months						12 Months or More						Total
		Fair			Unrealized			Fair			Unrealized			Fair		Unrealized
		Value			Losses			Value			Losses			Value		Losses
	December 31, 2014	(in thousands)
	U.S. government agency and government-sponsored enterprise mortgage-backed securities and collateralized mortgage obligations	$	258,825		$	(1,287	)	$	279,015		$	(6,924	)	$	537,840	(8,211		)
	State and municipal securities	71,026			(543		)	44,148			(982		)	115,174		(1,525		)
	U.S. government agency and government-sponsored enterprise securities	105,250			(518		)	216,221			(3,551		)	321,471		(4,069		)
	U.S. government securities	—			—			19,450			(411		)	19,450		(411		)
	Other securities	2,313			(2		)	2,834			(121		)	5,147		(123		)
	Total	$	437,414		$	(2,350	)	$	561,668		$	(11,989	)	$	999,082	$	(14,339	)
	December 31, 2013
	U.S. government agency and government-sponsored enterprise mortgage-backed securities and collateralized mortgage obligations	$	492,921		$	(10,991	)	$	121,303		$	(12,684	)	$	614,224	$	(23,675	)
	State and municipal securities	112,400			(3,069		)	13,815			(923		)	126,215		(3,992		)
	U.S. government agency and government-sponsored enterprise securities	260,001			(8,063		)	28,447			(2,003		)	288,448		(10,066		)
	U.S. government securities	20,114			(967		)	—			—			20,114		(967		)
	Other securities	2,257			(58		)	2,783			(173		)	5,040		(231		)
	Total	$	887,693		$	(23,148	)	$	166,348		$	(15,783	)	$	1,054,041	$	(38,931	)

Loans_Tables

Loans (Tables)	12 Months Ended
	Dec. 31, 2014
Financing Receivable, Recorded Investment [Line Items]
Analysis of Loan Portfolio by Major Types of Loans	The following is an analysis of the loan portfolio by major types of loans (net of unearned income):
		December 31, 2014												December 31, 2013
		Loans, excluding PCI loans				PCI Loans				Total				Loans, excluding PCI loans				PCI Loans				Total
		(in thousands)
	Commercial business	$	2,119,565			$	44,505			$	2,164,070			$	1,561,782			$	60,942			$	1,622,724
	Real estate:
	One-to-four family residential	175,571				26,993				202,564				108,317				33,943				142,260
	Commercial and multifamily residential	2,363,541				128,769				2,492,310				2,080,075				154,191				2,234,266
	Total real estate	2,539,112				155,762				2,694,874				2,188,392				188,134				2,376,526
	Real estate construction:
	One-to-four family residential	116,866				4,021				120,887				54,155				13,313				67,468
	Commercial and multifamily residential	134,443				2,321				136,764				126,390				5,373				131,763
	Total real estate construction	251,309				6,342				257,651				180,545				18,686				199,231
	Consumer	364,182				23,975				388,157				357,014				30,083				387,097
	Less: Net unearned income	(59,374		)		—				(59,374		)		(68,282		)		—				(68,282		)
	Total loans, net of unearned income	5,214,794				230,584				5,445,378				4,219,451				297,845				4,517,296
	Less: Allowance for loan and lease losses	(53,233		)		(16,336		)		(69,569		)		(52,280		)		(20,174		)		(72,454		)
	Total loans, net	$	5,161,561			$	214,248			$	5,375,809			$	4,167,171			$	277,671			$	4,444,842
	Loans held for sale	$	1,116			$	—			$	1,116			$	735			$	—			$	735
Analysis of Nonaccrual Loans	The following is an analysis of nonaccrual loans as of December 31, 2014 and 2013:
		December 31, 2014								December 31, 2013
		Recorded				Unpaid Principal				Recorded				Unpaid Principal
		Investment				Balance				Investment				Balance
		Nonaccrual				Nonaccrual				Nonaccrual				Nonaccrual
		Loans				Loans				Loans				Loans
		(in thousands)
	Commercial business:
	Secured	$	16,552			$	21,453			$	12,433			$	19,186
	Unsecured	247				269				176				202
	Real estate:
	One-to-four family residential	2,822				5,680				2,667				4,678
	Commercial and multifamily residential:
	Commercial land	821				1,113				442				783
	Income property	3,200				5,521				4,267				5,383
	Owner occupied	3,826				5,837				6,334				7,486
	Real estate construction:
	One-to-four family residential:
	Land and acquisition	95				112				3,246				6,601
	Residential construction	370				370				459				1,928
	Commercial and multifamily residential:
	Owner occupied	480				489				—				—
	Consumer	2,939				3,930				3,991				6,187
	Total	$	31,352			$	44,774			$	34,015			$	52,434
Loans, Excluding Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Analysis of the Aged Loan Portfolio	The following is an aging of the recorded investment of the loan portfolio as of December 31, 2014 and 2013:
		Current				30 - 59				60 - 89				Greater				Total				Nonaccrual			Total Loans
		Loans				Days				Days				than 90				Past Due				Loans
						Past Due				Past Due				Days Past
														Due
	December 31, 2014	(in thousands)
	Commercial business:
	Secured	$	2,004,418			$	5,137			$	6,149			$	1,372			$	12,658			$	16,552		$	2,033,628
	Unsecured	79,661				185				—				—				185				247			80,093
	Real estate:
	One-to-four family residential	167,197				1,700				45				—				1,745				2,822			171,764
	Commercial and multifamily residential:
	Commercial land	187,470				1,454				34				—				1,488				821			189,779
	Income property	1,294,982				3,031				786				—				3,817				3,200			1,301,999
	Owner occupied	839,689				937				289				—				1,226				3,826			844,741
	Real estate construction:
	One-to-four family residential:
	Land and acquisition	15,462				953				—				—				953				95			16,510
	Residential construction	97,821				326				—				4				330				370			98,521
	Commercial and multifamily residential:
	Income property	73,783				—				—				—				—				—			73,783
	Owner occupied	57,470				—				994				—				994				480			58,944
	Consumer	341,032				933				118				10				1,061				2,939			345,032
	Total	$	5,158,985			$	14,656			$	8,415			$	1,386			$	24,457			$	31,352		$	5,214,794
		Current				30 - 59				60 - 89				Greater				Total				Nonaccrual			Total Loans
		Loans				Days				Days				than 90				Past Due				Loans
						Past Due				Past Due				Days Past
														Due
	December 31, 2013	(in thousands)
	Commercial business:
	Secured	$	1,457,820			$	12,713			$	681			$	—			$	13,394			$	12,433		$	1,483,647
	Unsecured	72,255				156				17				—				173				176			72,604
	Real estate:
	One-to-four family residential	100,591				1,993				641				—				2,634				2,667			105,892
	Commercial and multifamily residential:
	Commercial land	142,034				—				358				—				358				442			142,834
	Income property	1,138,732				144				3,289				—				3,433				4,267			1,146,432
	Owner occupied	749,561				4,714				—				—				4,714				6,334			760,609
	Real estate construction:
	One-to-four family residential:
	Land and acquisition	8,225				199				—				—				199				3,246			11,670
	Residential construction	41,533				—				—				—				—				459			41,992
	Commercial and multifamily residential:
	Income property	86,521				—				—				—				—				—			86,521
	Owner occupied	38,916				—				—				—				—				—			38,916
	Consumer	322,685				835				823				—				1,658				3,991			328,334
	Total	$	4,158,873			$	20,754			$	5,809			$	—			$	26,563			$	34,015		$	4,219,451
Impaired Financing Receivables	The following is an analysis of the impaired loans (see Note 1) as of December 31, 2014 and 2013:
		Recorded Investment				Recorded Investment				Impaired Loans With												Impaired Loans Without
		of Loans				of Loans				Recorded Allowance												Recorded Allowance
		Collectively Measured				Individually
		for Contingency				Measured for
		Provision				Specific
						Impairment				Recorded				Unpaid				Related				Recorded			Unpaid
										Investment				Principal				Allowance				Investment			Principal
														Balance											Balance
	December 31, 2014	(in thousands)
	Commercial business:
	Secured	$	2,023,104			$	10,524			$	99			$	99			$	25			$	10,425		$	12,410
	Unsecured	80,091				2				2				2				2				—			—
	Real estate:
	One-to-four family residential	169,619				2,145				424				465				120				1,721			2,370
	Commercial and multifamily residential:
	Commercial land	189,779				—				—				—				—				—			—
	Income property	1,295,650				6,349				—				—				—				6,349			10,720
	Owner occupied	835,895				8,846				582				582				27				8,264			12,732
	Real estate construction:
	One-to-four family residential:
	Land and acquisition	16,401				109				109				109				67				—			—
	Residential construction	98,521				—				—				—				—				—			—
	Commercial and multifamily residential:
	Income property	73,783				—				—				—				—				—			—
	Owner occupied	58,944				—				—				—				—				—			—
	Consumer	344,908				124				—				—				—				124			201
	Total	$	5,186,695			$	28,099			$	1,216			$	1,257			$	241			$	26,883		$	38,433
		Recorded Investment				Recorded Investment				Impaired Loans With												Impaired Loans Without
		of Loans				of Loans				Recorded Allowance												Recorded Allowance
		Collectively Measured				Individually
		for Contingency				Measured for
		Provision				Specific
						Impairment				Recorded				Unpaid				Related				Recorded			Unpaid
										Investment				Principal				Allowance				Investment			Principal
														Balance											Balance
	December 31, 2013	(in thousands)
	Commercial business:
	Secured	$	1,478,560			$	5,087			$	2,866			$	2,885			$	343			$	2,221		$	2,560
	Unsecured	72,569				35				35				35				35				—			—
	Real estate:
	One-to-four family residential	104,272				1,620				442				479				138				1,178			2,119
	Commercial and multifamily residential:
	Commercial land	142,719				115				—				—				—				115			398
	Income property	1,140,019				6,413				918				933				26				5,495			7,885
	Owner occupied	749,601				11,008				3,802				3,817				1,073				7,206			10,464
	Real estate construction:
	One-to-four family residential
	Land and acquisition	9,726				1,944				113				113				71				1,831			2,587
	Residential construction	41,992				—				—				—				—				—			—
	Commercial and multifamily residential:
	Income property	86,521				—				—				—				—				—			—
	Owner occupied	38,916				—				—				—				—				—			—
	Consumer	328,167				167				23				27				4				144			210
	Total	$	4,193,062			$	26,389			$	8,199			$	8,289			$	1,690			$	18,190		$	26,223
	The following table provides additional information on impaired loans for the years ended December 31, 2014, 2013 and 2012:
		Year ended December 31, 2014								Year Ended December 31, 2013								Year ended December 31, 2012
		Average Recorded				Interest Recognized				Average Recorded				Interest Recognized				Average Recorded				Interest Recognized
		Investment				on				Investment				on				Investment				on
		Impaired Loans				Impaired Loans				Impaired Loans				Impaired Loans				Impaired Loans				Impaired Loans
		(in thousands)
	Commercial business
	Secured	$	7,345			$	36			$	5,636			$	19			$	8,978			$	9
	Unsecured	19				1				61				3				113				6
Real estate:
One-to-four family residential	2,094				49				1,665				63				2,130				—
Commercial & multifamily residential
Commercial land	82				—				1,691				—				3,124				—
Income property	6,782				270				8,910				238				7,895				77
Owner occupied	9,472				956				10,779				971				13,315				1,004
Real estate construction:
One-to-four family residential
Land and acquisition	694				6				2,624				6				4,465				—
Residential construction	—				—				420				—				3,223				11
Commercial & multifamily residential
Income property	—				—				—				—				3,169				—
Consumer	147				9				253				6				1,112				7
Total	$	26,635			$	1,327			$	32,039			$	1,306			$	47,524			$	1,114
Analysis of loans classified as Troubled Debt Restructurings (“TDR”)	The following is an analysis of loans classified as troubled debt restructurings (“TDR”) for the years ended December 31, 2014, 2013 and 2012:
		Year ended December 31, 2014											Year Ended December 31, 2013											Year ended December 31, 2012
		Number of TDR Modifications			Pre-Modification				Post-Modification				Number of TDR Modifications			Pre-Modification				Post-Modification				Number of TDR Modifications		Pre-Modification		Post-Modification
					Outstanding				Outstanding							Outstanding				Outstanding						Outstanding		Outstanding
					Recorded				Recorded							Recorded				Recorded						Recorded		Recorded
					Investment				Investment							Investment				Investment						Investment		Investment
		(dollars in thousands)
	Commercial business:
	Secured	4			$	759			$	759			2			$	190			$	190			1		$	195	$	194
	Real estate:
	One-to-four family residential	2			494				494				1			113				113				—		—		—
	Commercial and multifamily residential:
	Commercial land	—			—				—				1			137				137				—		—		—
	Income property	1			143				126				4			1,186				1,186				1		4,279		2,650
	Owner occupied	1			1,496				1,496				1			172				172				—		—		—
	Real estate construction:
	One-to-four family residential:
	Land and acquisition	—			—				—				1			117				117				—		—		—
	Consumer	—			—				—				2			53				53				—		—		—
	Total	8			$	2,892			$	2,875			12			$	1,968			$	1,968			2		$	4,474	$	2,844
Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Analysis of Loan Portfolio by Major Types of Loans	The following is an analysis of our PCI loans, net of related allowance for losses as of December 31, 2014 and 2013:
		December 31, 2014				December 31, 2013
		(in thousands)
	Commercial business	$	50,334			$	72,870
	Real estate:
	One-to-four family residential	31,981				41,642
	Commercial and multifamily residential	140,398				170,879
	Total real estate	172,379				212,521
	Real estate construction:
	One-to-four family residential	4,353				14,781
	Commercial and multifamily residential	2,588				6,869
	Total real estate construction	6,941				21,650
	Consumer	26,814				34,101
	Subtotal of purchased credit impaired loans	256,468				341,142
	Less:
	Valuation discount resulting from acquisition accounting	25,884				43,297
	Allowance for loan losses	16,336				20,174
	PCI loans, net of valuation discounts and allowance for loan losses	$	214,248			$	277,671
Changes in Accretable Yield for Acquired Loans [Table Text Block]	The following table shows the changes in accretable yield for acquired loans for the years ended December 31, 2014, 2013, and 2012:
		Years Ended December 31,
		2014				2013				2012
		(in thousands)
	Balance at beginning of period	$	103,907			$	166,888			$	259,669
	Accretion	(36,066		)		(51,816		)		(86,671		)
	Disposals	(3,386		)		(6,898		)		(12,856		)
	Reclassifications from nonaccretable difference	9,394				(4,267		)		6,746
	Balance at end of period	$	73,849			$	103,907			$	166,888

Allowance_for_Loan_and_Lease_L1

Allowance for Loan and Lease Losses and Unfunded Commitments and Letters of Credit (Tables)	12 Months Ended
	Dec. 31, 2014
Financing Receivable, Allowance for Credit Losses [Line Items]
Changes in the Allowance for Loan and Lease Losses	The following tables show a detailed analysis of the allowance for loan and lease losses for loans for the years ended December 31, 2014, 2013 and 2012:
		Beginning		Charge-offs			Recoveries		Provision (Recovery)			Ending		Specific		General
		Balance										Balance		Reserve		Allocation
	Year ended December 31, 2014	(in thousands)
	Commercial business:
	Secured	$	31,027	$	(4,159	)	$	2,637	$	(3,582	)	$	25,923	$	25	$	25,898
	Unsecured	696		(130		)	370		(9		)	927		2		925
	Real estate:
	One-to-four family residential	1,252		(230		)	159		1,100			2,281		120		2,161
	Commercial and multifamily residential:
	Commercial land	489		(29		)	70		269			799		—		799
	Income property	9,234		(1,934		)	819		1,040			9,159		—		9,159
	Owner occupied	3,605		(1,030		)	51		2,381			5,007		27		4,980
	Real estate construction:
	One-to-four family residential:
	Land and acquisition	610		—			740		(153		)	1,197		67		1,130
	Residential construction	822		—			1,190		(152		)	1,860		—		1,860
	Commercial and multifamily residential:
	Income property	285		—			—		337			622		—		622
	Owner occupied	58		—			—		376			434		—		434
	Consumer	2,547		(2,774		)	1,353		2,054			3,180		—		3,180
	Purchased credit impaired	20,174		(14,436		)	7,721		2,877			16,336		—		16,336
	Unallocated	1,655		—			—		189			1,844		—		1,844
	Total	$	72,454	$	(24,722	)	$	15,110	$	6,727		$	69,569	$	241	$	69,328
		Beginning		Charge-offs			Recoveries		Provision (Recovery)			Ending		Specific		General
		Balance										Balance		Reserve		Allocation
	Year Ended December 31, 2013	(in thousands)
	Commercial business:
	Secured	$	27,270	$	(4,148	)	$	1,512	$	6,393		$	31,027	$	343	$	30,684
	Unsecured	753		(794		)	932		(195		)	696		35		661
	Real estate:
	One-to-four family residential	694		(228		)	270		516			1,252		138		1,114
	Commercial and multifamily residential:
	Commercial land	460		(20		)	169		(120		)	489		—		489
	Income property	11,033		(1,405		)	489		(883		)	9,234		26		9,208
	Owner occupied	6,362		(1,118		)	375		(2,014		)	3,605		1,073		2,532
	Real estate construction:
	One-to-four family residential:
	Land and acquisition	1,171		(32		)	2,553		(3,082		)	610		71		539
	Residential construction	635		(101		)	112		176			822		—		822
	Commercial and multifamily residential:
	Income property	316		—			—		(31		)	285		—		285
	Owner occupied	102		—			—		(44		)	58		—		58
	Consumer	2,437		(2,242		)	552		1,800			2,547		4		2,543
	Purchased credit impaired	30,056		(13,853		)	7,232		(3,261		)	20,174		—		20,174
	Unallocated	1,011		—			—		644			1,655		—		1,655
	Total	$	82,300	$	(23,941	)	$	14,196	$	(101	)	$	72,454	$	1,690	$	70,764
		Beginning		Charge-offs			Recoveries		Provision (Recovery)			Ending		Specific		General
		Balance										Balance		Reserve		Allocation
	Year ended December 31, 2012	(in thousands)
	Commercial business:
	Secured	$	24,745	$	(10,029	)	$	1,354	$	11,200		$	27,270	$	113	$	27,157
	Unsecured	689		(144		)	194		14			753		92		661
	Real estate:
	One-to-four family residential	654		(549		)	285		304			694		112		582
	Commercial and multifamily residential:
	Commercial land	488		(526		)	63		435			460		—		460
	Income property	9,551		(4,030		)	905		4,607			11,033		1,040		9,993
	Owner occupied	9,606		(918		)	631		(2,957		)	6,362		38		6,324
	Real estate construction:
	One-to-four family residential:
	Land and acquisition	2,331		(989		)	1,059		(1,230		)	1,171		—		1,171
	Residential construction	864		(617		)	429		(41		)	635		—		635
	Commercial and multifamily residential:
Income property	665		(93		)	66		(322		)	316		—		316
Owner occupied	35		—			—		67			102		—		102
Consumer	2,719		(2,534		)	1,171		1,081			2,437		—		2,437
Purchased credit impaired	4,944		(5,112		)	4,332		25,892			30,056		—		30,056
Unallocated	694		—			—		317			1,011		—		1,011
Total	$	57,985	$	(25,541	)	$	10,489	$	39,367		$	82,300	$	1,395	$	80,905
Changes in the Allowance for Unfunded Commitments and Letters of Credit	Changes in the allowance for unfunded commitments and letters of credit, a component of other liabilities in the consolidated balance sheet, are summarized as follows:
		Years Ended December 31,
		2014		2013			2012
		(in thousands)
	Beginning balance	$	2,505	$	1,915		$	1,535
	Net changes in the allowance for unfunded commitments and letters of credit	150		590			380
	Ending balance	$	2,655	$	2,505		$	1,915
Financing Receivable Credit Quality Indicators [Table Text Block]	The following is an analysis of the credit quality of our loan portfolio, excluding PCI loans as of December 31, 2014 and 2013:
		Pass		Special Mention			Substandard		Doubtful			Loss		Total
	December 31, 2014	(in thousands)
	Loans, excluding PCI loans
	Commercial business:
	Secured	$	1,963,210	$	15,790		$	54,628	$	—		$	—	$	2,033,628
	Unsecured	79,534		—			559		—			—		80,093
	Real estate:
	One-to-four family residential	163,914		55			7,795		—			—		171,764
	Commercial and multifamily residential:
	Commercial land	183,701		4,217			1,861		—			—		189,779
	Income property	1,287,729		5,885			8,385		—			—		1,301,999
	Owner occupied	825,694		7,876			11,171		—			—		844,741
	Real estate construction:
	One-to-four family residential:
	Land and acquisition	15,307		167			1,036		—			—		16,510
	Residential construction	96,031		909			1,581		—			—		98,521
	Commercial and multifamily residential:
	Income property	73,783		—			—		—			—		73,783
	Owner occupied	58,055		—			889		—			—		58,944
	Consumer	339,695		68			5,269		—			—		345,032
	Total	$	5,086,653	$	34,967		$	93,174	$	—		$	—	5,214,794
	Less:
	Allowance for loan losses													53,233
	Loans, excluding PCI loans, net													$	5,161,561
		Pass		Special Mention			Substandard		Doubtful			Loss		Total
	December 31, 2013	(in thousands)
	Loans, excluding PCI loans
	Commercial business:
	Secured	$	1,372,038	$	43,309		$	68,300	$	—		$	—	$	1,483,647
	Unsecured	72,226		199			179		—			—		72,604
	Real estate:
	One-to-four family residential	98,626		1,567			5,699		—			—		105,892
	Commercial and multifamily residential:
	Commercial land	137,850		—			4,984		—			—		142,834
	Income property	1,108,033		5,473			32,926		—			—		1,146,432
	Owner occupied	748,725		—			11,884		—			—		760,609
	Real estate construction:
	One-to-four family residential:
	Land and acquisition	7,526		—			4,144		—			—		11,670
	Residential construction	36,270		2,352			3,370		—			—		41,992
	Commercial and multifamily residential:
	Income property	86,206		—			315		—			—		86,521
	Owner occupied	38,916		—			—		—			—		38,916
	Consumer	321,348		331			6,188		467			—		328,334
	Total	$	4,027,764	$	53,231		$	137,989	$	467		$	—	4,219,451
	Less:
	Allowance for loan losses													52,280
	Loans, excluding PCI loans, net													$	4,167,171
	The following is an analysis of the credit quality of our PCI loan portfolio as of December 31, 2014 and 2013:
		Pass		Special Mention			Substandard		Doubtful			Loss		Total
	December 31, 2014	(in thousands)
	PCI loans:
	Commercial business:
	Secured	$	37,927	$	937		$	9,223	$	—		$	—	$	48,087
	Unsecured	2,156		—			91		—			—		2,247
	Real estate:
	One-to-four family residential	28,822		—			3,159		—			—		31,981
	Commercial and multifamily residential:
	Commercial land	9,104		—			6,240		—			—		15,344
	Income property	51,435		1,892			7,186		—			—		60,513
	Owner occupied	58,629		346			5,566		—			—		64,541
	Real estate construction:
	One-to-four family residential:
Land and acquisition	1,595		—			913		—			—		2,508
Residential construction	741		—			1,104		—			—		1,845
Commercial and multifamily residential:
Income property	1,435		—			227		—			—		1,662
Owner occupied	926		—			—		—			—		926
Consumer	24,037		—			2,777		—			—		26,814
Total	$	216,807	$	3,175		$	36,486	$	—		$	—	256,468
Less:
Valuation discount resulting from acquisition accounting													25,884
Allowance for loan losses													16,336
PCI loans, net													$	214,248
	Pass		Special Mention			Substandard		Doubtful			Loss		Total
December 31, 2013	(in thousands)
PCI loans:
Commercial business:
Secured	$	48,510	$	2,849		$	18,291	$	—		$	—	$	69,650
Unsecured	2,732		396			92		—			—		3,220
Real estate:
One-to-four family residential	35,066		1,842			4,734		—			—		41,642
Commercial and multifamily residential:
Commercial land	10,778		198			7,589		—			—		18,565
Income property	55,985		3,950			10,657		—			—		70,592
Owner occupied	67,653		111			13,958		—			—		81,722
Real estate construction:
One-to-four family residential:
Land and acquisition	4,674		2,739			1,936		—			—		9,349
Residential construction	3,008		—			2,424		—			—		5,432
Commercial and multifamily residential:
Income property	3,806		—			1,709		—			—		5,515
Owner occupied	1,074		—			280		—			—		1,354
Consumer	30,722		33			3,319		27			—		34,101
Total	$	264,008	$	12,118		$	64,989	$	27		$	—	341,142
Less:
Valuation discount resulting from acquisition accounting													43,297
Allowance for loan losses													20,174
PCI loans, net													$	277,671

Other_Real_Estate_Owned_Tables

Other Real Estate Owned (Tables)	12 Months Ended
	Dec. 31, 2014
Other Real Estate, Foreclosed Assets, and Repossessed Assets [Abstract]
Summary of Other Real Estate Owned	The following table sets forth activity in OREO for the period:
		December 31, 2014			31-Dec-13
		(in thousands)
	Balance, beginning of period	$	35,927		$	26,987
	Established through acquisitions	2,752			14,708
	Transfers in, net of write-downs ($0 and $90, respectively)	10,200			18,100
	Additions to OREO	—			3,577
	Additional OREO write-downs	(4,039		)	(2,035		)
	Proceeds from sale of OREO property	(28,559		)	(35,949		)
	Net gain on sale of OREO	5,909			10,539
	Total OREO, end of period	$	22,190		$	35,927

FDIC_Losssharing_Asset_and_Cov1

FDIC Loss-sharing Asset and Covered Assets (Tables)	12 Months Ended
	Dec. 31, 2014
Covered Assets And FDIC Loss Sharing Asset [Line Items]
FDIC Loss-sharing Asset	The following table shows a detailed analysis of the FDIC loss-sharing asset for the years ending December 31, 2014 and 2013:
		2014			2013
		(in thousands)
	Balance at beginning of period	$	39,846		$	96,354
	Adjustments not reflected in income:
	Cash received from the FDIC, net	(2,499		)	(9,246		)
	FDIC reimbursable recoveries, net	(2,184		)	(2,245		)
	Adjustments reflected in income:
	Amortization, net	(21,279		)	(36,729		)
	Loan impairment (recapture)	2,301			(2,609		)
	Sale of other real estate	(2,179		)	(6,177		)
	Write-downs of other real estate	1,065			364
	Other	103			134
	Balance at end of period	$	15,174		$	39,846
Schedule of FDIC Loss-Sharing Agreements and Covered Assets [Table Text Block]	The following table presents information about the composition of the FDIC loss-sharing asset, the clawback liability, and the non-single family and the single family covered assets as of the date indicated:
		December 31, 2014
		Columbia River Bank			American Marine Bank			Summit Bank		First Heritage Bank		Total
		(in thousands)
	FDIC loss-sharing asset	$	1,183		$	4,927		$	4,712	$	4,352	$	15,174
	Clawback liability	$	4,017		$	157		$	—	$	—	$	4,174
	Non-single family covered assets	$	115,230		$	17,984		$	14,352	$	27,281	$	174,847
	Single family covered assets	$	11,166		$	26,587		$	6,530	$	2,516	$	46,799
	Loss-sharing expiration dates:
	Non-single family	First Quarter 2015			First Quarter 2015			Second Quarter 2016		Second Quarter 2016
	Single family	First Quarter 2020			First Quarter 2020			Second Quarter 2021		Second Quarter 2021
	Loss recovery expiration dates:
	Non-single family	First Quarter 2018			First Quarter 2018			Second Quarter 2019		Second Quarter 2019
	Single family	First Quarter 2020			First Quarter 2020			Second Quarter 2021		Second Quarter 2021

Premises_and_Equipment_Tables

Premises and Equipment (Tables)	12 Months Ended
	Dec. 31, 2014
Property, Plant and Equipment [Abstract]
Property, Plant and Equipment	accumulated depreciation and amortization, were as follows:
		December 31,
		2014			2013
		(in thousands)
	Land	$	52,338		$	48,992
	Buildings	103,240			94,878
	Leasehold improvements	21,199			14,254
	Furniture and equipment	28,486			29,465
	Vehicles	596			546
	Computer software	15,666			17,490
	Total cost	221,525			205,625
	Less accumulated depreciation and amortization	(49,435		)	(50,893		)
	Total	$	172,090		$	154,732

Goodwill_and_Intangible_Assets1

Goodwill and Intangible Assets (Tables)	12 Months Ended
	Dec. 31, 2014
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of Goodwill and Intangible Assets	The following table sets forth activity for goodwill and other intangible assets for the period:
		Years Ended December 31,
		2014			2013			2012
		(in thousands)
	Total goodwill, beginning of period	$	343,952		$	115,554		$	115,554
	Established through acquisitions	38,585			228,398			—
	Total goodwill, end of period	382,537			343,952			115,554
	Other intangible assets, net
	Core deposit intangible:
	Gross core deposit intangible balance, beginning of period	47,698			32,441			32,441
	Accumulated amortization, beginning of period	(22,765		)	(16,720		)	(12,275		)
	Core deposit intangible, net, beginning of period	24,933			15,721			20,166
	Established through acquisitions	10,900			15,257			—
	CDI current period amortization	(6,293		)	(6,045		)	(4,445		)
	Total core deposit intangible, end of period	29,540			24,933			15,721
	Intangible assets not subject to amortization	919			919			—
	Other intangible assets, net at end of period	30,459			25,852			15,721
	Total goodwill and intangible assets, end of period	$	412,996		$	369,804		$	131,275
Estimated Future Amortization Expense of Core Deposit Intangibles	The following table provides the estimated future amortization expense of core deposit intangibles for the succeeding five years:
	Years Ending December 31,	(in thousands)
	2015	$	6,882
	2016	5,945
	2017	4,913
	2018	3,855
	2019	2,951

Deposits_Tables

Deposits (Tables)	12 Months Ended
	Dec. 31, 2014
Deposits [Abstract]
Schedule Of Deposits	Year-end deposits are summarized in the following table:
		December 31,
		2014		2013
		(in thousands)
	Core deposits:
	Demand and other noninterest-bearing	$	2,651,373	$	2,171,703
	Interest-bearing demand	1,304,258		1,170,006
	Money market	1,760,331		1,569,261
	Savings	615,721		496,444
	Certificates of deposit less than $100,000	288,261		288,943
	Total core deposits	6,619,944		5,696,357
	Certificates of deposit greater than $100,000	202,014		201,498
	Certificates of deposit insured through CDARS®	18,429		19,488
	Brokered money market accounts	83,402		41,765
	Subtotal	6,923,789		5,959,108
	Valuation adjustment resulting from acquisition accounting	933		367
	Total deposits	$	6,924,722	$	5,959,475
Schedule Of Time Deposits Maturity	The following table shows the amount and maturity of time deposits that had balances of $100,000 or greater:
	Years Ending December 31,	(in thousands)
	2015	$	162,828
	2016	40,375
	2017	8,069
	2018	3,822
	2019	3,982
	Thereafter	108
	Total	$	219,184

Federal_Home_Loan_Bank_and_Fed1

Federal Home Loan Bank and Federal Reserve Bank Borrowings (Tables)	12 Months Ended
	Dec. 31, 2014
Federal Home Loan Bank Advances [Member]
Debt Instrument [Line Items]
Schedule of Maturities of Long-term Debt	At December 31, 2014 FHLB advances were scheduled to mature as follows:
		Federal Home Loan Bank Advances
		Fixed rate advances
		Weighted Average Rate			Amount
		(dollars in thousands)
	Within 1 year	0.27	%		$	210,000
	Over 1 through 5 years	5.66	%		1,000
	Due after 10 years	5.37	%		5,000
	Total				216,000
	Valuation adjustment from acquisition accounting				568
	Total				$	216,568
Debt Instrument Activity For Year	The maximum, average outstanding and year-end balances and average interest rates on advances from the FHLB were as follows for the years ended December 31, 2014, 2013 and 2012:
		Years ended December 31,
		2014				2013			2012
		(dollars in thousands)
	Balance at end of year	$	216,568			$	36,606		$	6,644
	Average balance during the year	$	44,876			$	51,030		$	100,337
	Maximum month-end balance during the year	$	216,568			$	190,631		$	118,967
	Weighted average rate during the year	0.74		%		1.12		%	2.79		%
	Weighted average rate at December 31	0.41		%		1.09		%	5.42		%
Schedule of Financial Instruments Owned and Pledged as Collateral	FHLB advances are collateralized by the following:
		December 31,
		2014				2013
		(in thousands)
	Recorded value of blanket pledge on loans receivable	$	1,083,879			$	1,075,389
	Total	$	1,083,879			$	1,075,389
	FHLB borrowing capacity	$	865,138			$	1,037,159
Federal Reserve Bank Advances [Member]
Debt Instrument [Line Items]
Debt Instrument Activity For Year	Although the Company has not had FRB borrowings in the last three years
Schedule of Financial Instruments Owned and Pledged as Collateral	The following table shows amounts pledged to the Federal Reserve Bank:
		December 31,
		2014				2013
		(in thousands)
	Fair value of investment securities	$	40,128			$	40,210
	Recorded value of pledged commercial loans	46,002				45,242
	Total	$	86,130			$	85,452
	Federal Reserve Bank borrowing capacity	$	86,130			$	85,452

Derivatives_and_Balance_Sheet_1

Derivatives and Balance Sheet Offsetting (Tables)	12 Months Ended
	Dec. 31, 2014
Derivative [Line Items]
Balance Sheet Offsetting [Table Text Block]	The following tables show the gross interest rate swap agreements and repurchase agreements in the consolidated balance sheets and the respective collateral received or pledged in the form of other financial instruments, which are generally marketable securities. The collateral amounts in these tables are limited to the outstanding balances of the related asset or liability. Therefore, instances of overcollateralization are not shown.
		Gross Amounts of Recognized Assets/Liabilities				Gross Amounts Offset in the Consolidated Balance Sheets			Net Amounts of Assets/Liabilities Presented in the Consolidated Balance Sheets		Gross Amounts Not Offset in the Consolidated Balance Sheets
											Collateral Posted				Net Amount
	December 31, 2014	(in thousands)
	Assets
	Interest rate contracts	$	11,800			$	—		$	11,800	$	—			$	11,800
	Liabilities
	Interest rate contracts	$	11,851			$	—		$	11,851	$	(11,851	)		$	—
	Repurchase agreements	$	105,080			$	—		$	105,080	$	(105,080	)		$	—
	December 31, 2013
	Assets
	Interest rate contracts	$	9,044			$	—		$	9,044	$	—			$	9,044
	Liabilities
	Interest rate contracts	$	9,044			$	—		$	9,044	$	(9,044	)		$	—
	Repurchase agreements	$	25,000			$	—		$	25,000	$	(25,000	)		$	—
Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Schedule of Fair Value Derivative Instruments	The following table presents the fair value and balance sheet classification of derivatives not designated as hedging instruments at December 31, 2014 and 2013:
		Asset Derivatives									Liability Derivatives
		2014						2013			2014						2013
	(in thousands)	Balance Sheet		Fair Value				Balance Sheet	Fair Value		Balance Sheet		Fair Value				Balance Sheet	Fair Value
		Location						Location			Location						Location
	Interest rate contracts	Other assets		$	11,800			Other assets	$	9,044	Other liabilities		$	11,851			Other liabilities	$	9,044

Employee_Benefit_Plans_Tables

Employee Benefit Plans (Tables)	12 Months Ended
	Dec. 31, 2014
Employee Benefit [Line Items]
Schedule of Accumulated and Projected Benefit Obligations	The following table reconciles the accumulated liability for the projected benefit obligation:
		December 31,
		2014			2013
		(in thousands)
	Balance at beginning of year	$	16,423		$	11,616
	Established through acquisitions	511			3,398
	Change in actuarial loss	—			2,212
	Benefit expense	1,325			1,880
	Benefit payments	(1,718		)	(2,683		)
	Balance at end of year	$	16,541		$	16,423
SERP [Member]
Employee Benefit [Line Items]
Schedule of Expected Benefit Payments	The benefits expected to be paid in conjunction with the SERP are presented in the following table:
	Years Ending December 31,	(in thousands)
	2015	$	975
	2016	994
	2017	1,088
	2018	1,349
	2019	1,384
	2020 through 2024	9,580
	Total	$	15,370

Commitments_and_Contingent_Lia1

Commitments and Contingent Liabilities (Tables)	12 Months Ended
	Dec. 31, 2014
Commitments and Contingencies Disclosure [Abstract]
Schedule of Future Minimum Rental Payments for Operating Leases	As of December 31, 2014, minimum future rental payments, exclusive of taxes and other charges, of these leases were:
	Years Ending December 31,	(in thousands)
	2015	$	8,557
	2016	6,602
	2017	5,353
	2018	4,671
	2019	4,308
	Thereafter	18,121
	Total minimum payments	$	47,612

Accumulated_Other_Comprehensiv1

Accumulated Other Comprehensive Income (Tables)	12 Months Ended
	Dec. 31, 2014
Accumulated Other Comprehensive Income [Abstract]
Schedule of Accumulated Other Comprehensive Income (Loss) [Table Text Block]	The following table shows changes in accumulated other comprehensive income (loss) by component for the years ended December 31, 2014 and 2013:
		Unrealized Gains and Losses on Available-for-Sale Securities (1)			Unrealized Gains and Losses on Pension Plan Liability (1)			Total (1)
	Year ended December 31, 2014	(in thousands)
	Beginning balance	$	(10,108	)	$	(1,936	)	$	(12,044	)
	Other comprehensive income before reclassifications	17,922			—			17,922
	Amounts reclassified from accumulated other comprehensive income (2)	(352		)	95			(257		)
	Net current-period other comprehensive income	17,570			95			17,665
	Ending balance	$	7,462		$	(1,841	)	$	5,621
	Year Ended December 31, 2013
	Beginning balance	$	20,918		$	(769	)	$	20,149
	Other comprehensive loss before reclassifications	(30,727		)	(1,432		)	(32,159		)
	Amounts reclassified from accumulated other comprehensive income (2)	(299		)	265			(34		)
	Net current-period other comprehensive loss	(31,026		)	(1,167		)	(32,193		)
	Ending balance	$	(10,108	)	$	(1,936	)	$	(12,044	)
	__________
	(1) All amounts are net of tax. Amounts in parenthesis indicate debits.
	(2) See following table for details about these reclassifications.
Reclassification out of Accumulated Other Comprehensive Income [Table Text Block]	The following table shows details regarding the reclassifications from accumulated other comprehensive income for the years ended December 31, 2014 and :
		Amount Reclassified from Accumulated Other Comprehensive Income						Affected line Item in the Consolidated Statement of Income
		Years Ended
		December 31, 2014			December 31, 2013
		(in thousands)
	Unrealized gains and losses on available-for-sale securities	$	552		$	462		Investment securities gains, net
		552			462			Total before tax
		(200		)	(163		)	Income tax provision
		$	352		$	299		Net of tax
	Amortization of pension plan liability	$	(149	)	$	(400	)	Compensation and employee benefits
	actuarial losses
		(149		)	(400		)	Total before tax
		54			135			Income tax benefit
		$	(95	)	$	(265	)	Net of tax

Fair_Value_Accounting_and_Meas1

Fair Value Accounting and Measurement (Tables)	12 Months Ended
	Dec. 31, 2014
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Financial Assets And Liabilities Accounted For Fair Value On Recurring Basis	The following table sets forth the Company’s financial assets and liabilities that were accounted for at fair value on a recurring basis at December 31, 2014 and 2013 by level within the fair value hierarchy. Financial assets and liabilities are classified in their entirety based on the lowest level of input that is significant to the fair value measurement:
		Fair value  at		Fair Value Measurements at Reporting Date Using
		December 31, 2014		Level 1			Level 2		Level 3
		(in thousands)
	Assets
	Securities available for sale
	U.S. government agency and sponsored enterprise mortgage-back securities and collateralized mortgage obligations	$	1,162,387	$	—		$	1,162,387	$	—
	State and municipal securities	496,484		—			496,484		—
	U.S. government agency and government-sponsored enterprise securities	413,706		—			413,706		—
	U.S. government securities	20,499		20,499			—		—
	Other securities	5,181		—			5,181		—
	Total securities available for sale	$	2,098,257	$	20,499		$	2,077,758	$	—
	Other assets (Interest rate contracts)	$	11,800	$	—		$	11,800	$	—
	Liabilities
	Other liabilities (Interest rate contracts)	$	11,851	$	—		$	11,851	$	—
		Fair value  at		Fair Value Measurements at Reporting Date Using
		December 31, 2013		Level 1			Level 2		Level 3
		(in thousands)
	Assets
	Securities available for sale
	U.S. government agency and sponsored enterprise mortgage-back securities and collateralized mortgage obligations	$	948,408	$	—		$	948,408	$	—
	State and municipal debt securities	364,470		—			364,470		—
	U.S. government agency and government-sponsored enterprise securities	326,039		—			326,039		—
	U.S. government securities	20,114		20,114			—		—
	Other securities	5,080		—			5,080		—
	Total securities available for sale	$	1,664,111	$	20,114		$	1,643,997	$	—
	Other assets (Interest rate contracts)	$	9,044	$	—		$	9,044	$	—
	Liabilities
	Other liabilities (Interest rate contracts)	$	9,044	$	—		$	9,044	$	—
Financial Assets Accounted For Fair Value On Nonrecurring Basis	The following table sets forth the Company’s assets that were measured using fair value estimates on a nonrecurring basis during the years ended December 31, 2014 and 2013:
		Fair value  at		Fair Value Measurements at Reporting Date Using							Losses During the Year Ended
		December 31, 2014		Level 1			Level 2		Level 3		31-Dec-14
		(in thousands)
	OREO	$	5,365	$	—		$	—	$	5,365	$	1,008
		$	5,365	$	—		$	—	$	5,365	$	1,008
		Fair value  at		Fair Value Measurements at Reporting Date Using							Losses During the Year Ended
		December 31, 2013		Level 1			Level 2		Level 3		December 31, 2013
		(in thousands)
	Impaired loans	$	8,973	$	—		$	—	$	8,973	$	1,536
	OREO (1)	5,693		—			—		5,693		1,230
		$	14,666	$	—		$	—	$	14,666	$	2,766
	(1) Reclassified to conform to the current period’s presentation. The reclassification was limited to combining historically reported noncovered OREO and covered OREO into one line item for OREO.
Fair Value Inputs, Assets, Quantitative Information [Table Text Block]	The range and weighted-average of the significant unobservable inputs used to fair value our Level 3 nonrecurring assets during 2014 and 2013, along with the valuation techniques used, are shown in the following tables:
		Fair value  at		Valuation Technique		Unobservable Input	Range (Weighted Average) (1)
		December 31, 2014
		(dollars in thousands)
	OREO	$	5,365	Fair Market Value of Collateral		Adjustment to Appraisal Value	N/A (2)
	(1) Discount applied to appraisal value, letter of intent to purchase, or stated value (in the case of accounts receivable and inventory).
	(2) Quantitative disclosures are not provided for OREO because there were no adjustments made to the appraisal value during the current period.
		Fair value  at		Valuation Technique		Unobservable Input	Range (Weighted Average) (1)
		December 31, 2013
		(dollars in thousands)
	Impaired loans	$	8,973	Fair Market Value of Collateral		Adjustment to Appraisal Value	N/A (2)
	OREO (3)	5,693		Fair Market Value of Collateral		Adjustment to Appraisal Value	N/A (2)
	(1) Discount applied to appraisal value, letter of intent to purchase, or stated value (in the case of accounts receivable and inventory).
	(2) Quantitative disclosures are not provided for impaired loans and OREO because there were no adjustments made to the appraisal value during the current period.
	(3) Reclassified to conform to the current period’s presentation. The reclassification was limited to combining historically reported noncovered OREO and covered OREO into one line item for OREO.
Fair Value, by Balance Sheet Grouping	The following tables summarize carrying amounts and estimated fair values of selected financial instruments for the periods indicated:
		December 31,
		2014
		Carrying		Fair			Level 1		Level 2		Level 3
		Amount		Value
		(in thousands)
	Assets
	Cash and due from banks	$	171,221	$	171,221		$	171,221	$	—	$	—
	Interest-earning deposits with banks	16,949		16,949			16,949		—		—
	Securities available for sale	2,098,257		2,098,257			20,499		2,077,758		—
	FHLB stock	33,365		33,365			—		33,365		—
	Loans held for sale	1,116		1,116			—		1,116		—
	Loans	5,375,809		5,516,286			—		—		5,516,286
	FDIC loss-sharing asset	15,174		4,054			—		—		4,054
	Interest rate contracts	11,800		11,800			—		11,800		—
	Liabilities
	Deposits	$	6,924,722	$	6,921,804		$	6,416,017	$	505,787	$	—
	FHLB advances	216,568		217,296			—		217,296		—
	Repurchase agreements	105,080		106,171			—		106,171		—
	Other borrowings	8,248		8,248			—		8,248		—
	Interest rate contracts	11,851		11,851			—		11,851		—
		December 31,
		2013
		Carrying		Fair			Level 1		Level 2		Level 3
		Amount		Value
		(in thousands)
	Assets
	Cash and due from banks	$	165,030	$	165,030		$	165,030	$	—	$	—
	Interest-earning deposits with banks	14,531		14,531			14,531		—		—
	Securities available for sale	1,664,111		1,664,111			20,114		1,643,997		—
	FHLB stock	32,529		32,529			—		32,529		—
	Loans held for sale	735		735			—		735		—
	Loans	4,444,842		4,605,038			—		—		4,605,038
	FDIC loss-sharing asset	39,846		11,248			—		—		11,248
	Interest rate contracts	9,044		9,044			—		9,044		—
	Liabilities
	Deposits	$	5,959,475	$	5,958,747		$	5,449,546	$	509,201	$	—
	FHLB advances	36,606		35,080			—		35,080		—
	Repurchase agreements	25,000		26,361			—		26,361		—
	Interest rate contracts	9,044		9,044			—		9,044		—

Earnings_Per_Common_Share_Tabl

Earnings Per Common Share (Tables)	12 Months Ended
	Dec. 31, 2014
Earnings Per Share [Abstract]
Schedule of Basic and Diluted Earnings Per Share	The following table sets forth the computation of basic and diluted earnings per share for the periods indicated:
			Year Ended December 31,
			2014		2013		2012
			(in thousands except per share)
	Basic EPS:
	Net income		$	81,574	$	60,016	$	46,143
	Less: Earnings allocated to participating securities
	Preferred shares		157		95		—
	Nonvested restricted shares		780		523		443
	Earnings allocated to common shareholders		$	80,637	$	59,398	$	45,700
	Weighted average common shares outstanding		52,618		47,993		39,260
	Basic earnings per common share		$	1.53	$	1.24	$	1.16
	Diluted EPS:
	Earnings allocated to common shareholders (1)		$	80,640	$	59,407	$	45,700
	Weighted average common shares outstanding		52,618		47,993		39,260
	Dilutive effect of equity awards and warrants		565		1,058		3
	Weighted average diluted common shares outstanding		53,183		49,051		39,263
	Diluted earnings per common share		$	1.52	$	1.21	$	1.16
	Potentially dilutive share options that were not included in the computation of diluted EPS because to do so would be anti-dilutive		64		64		9
	__________
	-1	Earnings allocated to common shareholders for basic and diluted EPS may differ under the two-class method as a result of adding common stock equivalents for options and warrants to dilutive shares outstanding, which alters the ratio used to allocate earnings to common shareholders and participating securities for the purposes of calculating diluted EPS.

ShareBased_Payments_Tables

Share-Based Payments (Tables)	12 Months Ended
	Dec. 31, 2014
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Schedule of Nonvested Share Activity	A summary of changes in the Company’s nonvested shares and related information for the years ended December 31, 2014, 2013 and 2012 is presented below:
	Nonvested Shares	Shares		Weighted
				Average
				Grant-Date
				Fair Value
	Nonvested at January 1, 2012	362,675		$	19.24
	Granted	180,841		$	21.32
	Vested	(118,511	)	$	21.65
	Forfeited	(40,915	)	$	18.6
	Nonvested at December 31, 2012	384,090		$	19.54
	Granted	203,441		$	20.78
	Vested	(117,153	)	$	16.9
	Forfeited	(59,780	)	$	20.24
	Nonvested at December 31, 2013	410,598		$	20.79
	Granted	246,068		$	25.97
	Vested	(108,371	)	$	21.45
	Forfeited	(28,510	)	$	21.92
	Nonvested at December 31, 2014	519,785		$	23.03
Schedule of Share-based Compensation, Stock Options, Activity	A summary of option activity under the Plan as of December 31, 2014, and changes during the year then ended is presented below.
	Options	Shares		Weighted				Weighted	Aggregate
				Average				Average	Intrinsic
				Exercise				Remaining	Value
				Price				Contractual	$0
								Term
	Balance at December 31, 2013	116,197		$	65.01
	Forfeited	(8,753	)	$	75.32
	Expired	(22,330	)	$	91.95
	Exercised	(9,116	)	$	12.09
	Balance at December 31, 2014	75,998		$	62.41			2.4	$	391
	Vested or expected to vest at December 31, 2014	75,998		$	62.41			2.4	$	391
	Total Exercisable at December 31, 2014	75,998		$	62.41			2.4	$	391
Schedule of Share-based Compensation, Shares Authorized under Stock Option Plans, by Exercise Price Range	As of December 31, 2014, outstanding stock options consist of the following:
	Ranges of	Number of		Weighted Average		Weighted Average			Number of		Weighted Average
	Exercise Prices	Option		Remaining		Exercise Price of			Exercisable		Exercise Price of
		Shares		Contractual Life		Option Shares			Option Shares		Exercisable Option
											Shares
	$0.00 - $9.99	21,579		4.3		$	9.91		21,579		$	9.91
	$10.00 - $19.99	600		2.6		$	12.61		600		$	12.61
	$30.00 - $39.99	4,051		2.1		$	30.86		4,051		$	30.86
	$40.00 - $49.99	349		3.5		$	44.49		349		$	44.49
	$50.00 - $136.93	49,419		1.6		$	88.65		49,419		$	88.65
		75,998		2.4		$	62.41		75,998		$	62.41

Income_Tax_Tables

Income Tax (Tables)	12 Months Ended
	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Schedule of Components of Income Tax Expense (Benefit)	The components of income tax expense (benefit) are as follows:
		Years Ended December 31,
		2014			2013				2012
		(in thousands)
	Current tax expense	$	21,565		$	21,581			$	21,218
	Deferred tax expense (benefit)	14,646			5,413				(3,656		)
	Total	$	36,211		$	26,994			$	17,562
Schedule of Deferred Tax Assets and Liabilities	Significant components of the Company’s deferred tax assets and liabilities are as follows:
		December 31,
		2014			2013 (1)
		(in thousands)
	Deferred tax assets:
	Allowance for loan and lease losses	$	26,341		$	27,196
	Supplemental executive retirement plan	9,037			8,565
	Stock option and restricted stock	1,177			917
	OREO	1,101			7,929
	Nonaccrual interest	68			2,354
	Purchase accounting	15,272			15,551
	Unrealized loss on investment securities	—			7,176
	Net operating losses and credit carryforwards (1)	14,929			1,250
	Other (1)	532			491
	Total deferred tax assets	68,457			71,429
	Deferred tax liabilities:
	Asset purchase tax basis difference	(6,595		)	(7,754		)
	FHLB stock dividends	(4,086		)	(4,159		)
	Deferred loan fees	(4,691		)	(4,512		)
	Unrealized gain on investment securities	(2,987		)	—
	Depreciation	(5,394		)	(7,076		)
	Total deferred tax liabilities	(23,753		)	(23,501		)
	Net deferred tax asset	$	44,704		$	47,928
Schedule of Effective Income Tax Rate Reconciliation	A reconciliation of the Company’s effective income tax rate with the federal statutory tax rate is as follows:
		Years Ended December 31,
		2014						2013 (1)						2012 (1)
		Amount			Percent			Amount				Percent		Amount			Percent
		(dollars in thousands)
	Income tax based on statutory rate	$	41,225		35	%		$	30,454			35	%	$	22,297		35	%
	Reduction resulting from:
	Tax exempt instruments	(5,328		)	(5	)%		(4,113		)		(5	)%	(3,906		)	(6	)%
	Life insurance proceeds	(1,352		)	(1	)%		(1,250		)		(1	)%	(1,001		)	(2	)%
	Acquisition costs	448			—	%		1,362				2	%	—			—	%
	Other, net (1)	1,218			2	%		541				—	%	172			—	%
	Income tax provision	$	36,211		31	%		$	26,994			31	%	$	17,562		27	%

Regulatory_Capital_Requirement1

Regulatory Capital Requirements (Tables)	12 Months Ended
	Dec. 31, 2014
Regulatory Capital Requirements [Abstract]
Schedule of Compliance with Regulatory Capital Requirements under Banking Regulations	As of December 31, 2014, the most recent notification from the Federal Deposit Insurance Corporation categorized Columbia Bank as well capitalized under the regulatory framework for prompt corrective action. To be categorized as well capitalized, an institution must maintain minimum total risk-based, Tier 1 risk-based, and Tier 1 leverage ratios as set forth in the following tables. There are no conditions or events since the notification that management believes have changed Columbia Bank’s category. The Company and its banking subsidiary’s actual capital amounts and ratios as of December 31, 2014 and 2013, are also presented in the following table.
		Actual				For Capital				To Be Well
						Adequacy				Capitalized Under
						Purposes				Prompt
										Corrective Action
										Provision
		Amount		Ratio		Amount		Ratio		Amount		Ratio
		(dollars in thousands)
	As of December 31, 2014
	Total Capital (to risk-weighted assets):
	The Company	$	890,029	14.13	%	$	503,989	8	%	N/A		N/A
	Columbia Bank	$	860,755	13.67	%	$	503,852	8	%	$	629,816	10	%
	Tier 1 Capital (to risk-weighted assets):
	The Company	$	817,805	12.98	%	$	251,995	4	%	N/A		N/A
	Columbia Bank	$	788,531	12.52	%	$	251,926	4	%	$	377,889	6	%
	Tier 1 Capital (to average assets):
	The Company	$	817,805	10.57	%	$	309,579	4	%	N/A		N/A
	Columbia Bank	$	788,531	9.79	%	$	322,029	4	%	$	402,537	5	%
	As of December 31, 2013
	Total Capital (to risk-weighted assets):
	The Company	$	760,349	14.68	%	$	414,300	8	%	N/A		N/A
	Columbia Bank	$	700,099	13.52	%	$	414,238	8	%	$	517,797	10	%
	Tier 1 Capital (to risk-weighted assets):
	The Company	$	695,489	13.43	%	$	207,150	4	%	N/A		N/A
	Columbia Bank	$	635,248	12.27	%	$	207,119	4	%	$	310,678	6	%
	Tier 1 Capital (to average assets):
	The Company	$	695,489	10.19	%	$	272,891	4	%	N/A		N/A
	Columbia Bank	$	635,248	9.29	%	$	273,560	4	%	$	341,950	5	%

Parent_Company_Financial_Infor1

Parent Company Financial Information (Tables)	12 Months Ended
	Dec. 31, 2014
Condensed Financial Information of Parent Company Only Disclosure [Abstract]
Condensed Statements of Income - Parent Company Only	Condensed Statements of Income—Parent Company Only
		Years Ended December 31,
		2014			2013			2012
		(in thousands)
	Income
	Dividend from banking subsidiary	$	16,200		$	183,000		$	48,950
	Interest-earning deposits	25			68			153
	Other income	10			7			—
	Total income	16,235			183,075			49,103
	Expense
	Compensation and employee benefits	530			658			182
	Other borrowings	83			258			—
	Other expense	1,433			4,162			1,193
	Total expenses	2,046			5,078			1,375
	Income before income tax benefit and equity in undistributed net income (loss) of subsidiaries	14,189			177,997			47,728
	Income tax benefit	(704		)	(1,552		)	(435		)
	Income before equity in undistributed net income of subsidiaries	14,893			179,549			48,163
	Equity in undistributed net income (loss) of subsidiaries	66,681			(119,533		)	(2,020		)
	Net income	$	81,574		$	60,016		$	46,143
Condensed Balance Sheets - Parent Company Only	Condensed Balance Sheets—Parent Company Only
		December 31,
		2014			2013
		(in thousands)
	Assets
	Cash and due from banking subsidiary	$	10,322		$	3,006
	Interest-earning deposits	12,274			50,678
	Total cash and cash equivalents	22,596			53,684
	Investment in banking subsidiary	1,207,143			993,002
	Investment in other subsidiaries	5,351			5,037
	Other assets	5,273			1,952
	Total assets	$	1,240,363		$	1,053,675
	Liabilities and Shareholders’ Equity
	Other borrowings	$	8,248		$	—
	Other liabilities	3,940			426
	Total liabilities	12,188			426
	Shareholders’ equity	1,228,175			1,053,249
	Total liabilities and shareholders’ equity	$	1,240,363		$	1,053,675
Condensed Statements of Cash Flows - Parent Company Only	Condensed Statements of Cash Flows—Parent Company Only
		Years Ended December 31,
		2014			2013			2012
		(in thousands)
	Operating Activities
	Net income	$	81,574		$	60,016		$	46,143
	Adjustments to reconcile net income to net cash provided by operating activities:
	Equity in undistributed net loss (income) of subsidiaries	(66,681		)	119,533			2,020
	Stock-based compensation expense	2,859			2,844			1,622
	Net changes in other assets and liabilities	(403		)	6,830			(264		)
	Net cash provided by operating activities	17,349			189,223			49,521
	Investing Activities
	Net cash acquired (paid) in business combinations	10,277			(53,159		)	—
	Net cash provided by (used in) investing activities	10,277			(53,159		)	—
	Financing Activities
	Preferred stock dividends	(96		)	(32		)	—
	Common stock dividends	(49,494		)	(19,858		)	(38,824		)
	Repayment of other borrowings	(14,636		)	(51,000		)	—
	Exercise of warrants	5,000			—			—
	Purchase and retirement of common stock	(622		)	(429		)	—
	Proceeds from exercise of stock options	929			1,092			713
	Downstream stock offering proceeds to the Bank	—			(100,000		)	—
	Excess tax benefit associated with share-based compensation	205			1,203			—
	Net cash used in financing activities	(58,714		)	(169,024		)	(38,111		)
	Increase (decrease) in cash and cash equivalents	(31,088		)	(32,960		)	11,410
	Cash and cash equivalents at beginning of year	53,684			86,644			75,234
	Cash and cash equivalents at end of year	$	22,596		$	53,684		$	86,644

Summary_Of_Quarterly_Financial1

Summary Of Quarterly Financial Information (Unaudited) (Tables)	12 Months Ended
	Dec. 31, 2014
Quarterly Financial Information Disclosure [Abstract]
Schedule of Quarterly Financial Information	Quarterly financial information for the years ended December 31, 2014 and 2013 is summarized as follows:
		First			Second		Third		Fourth			Year Ended
		Quarter			Quarter		Quarter		Quarter			December 31,
		(in thousands, except per share amounts)
	2014
	Total interest income	$	74,925		$	76,087	$	77,133	$	79,897		$	308,042
	Total interest expense	985			963		913		1,133			3,994
	Net interest income	73,940			75,124		76,220		78,764			304,048
	Provision for loan and lease losses	1,922			2,117		980		1,708			6,727
	Noninterest income	14,008			14,627		15,930		15,185			59,750
	Noninterest expense	57,386			57,764		59,982		64,154			239,286
	Income before income taxes	28,640			29,870		31,188		28,087			117,785
	Provision for income taxes	8,796			8,643		9,605		9,167			36,211
	Net income	$	19,844		$	21,227	$	21,583	$	18,920		$	81,574
	Per common share (1)
	Earnings (basic)	$	0.38		$	0.4	$	0.41	$	0.34		$	1.53
	Earnings (diluted)	$	0.37		$	0.4	$	0.41	$	0.34		$	1.52
	2013
	Total interest income	$	54,761		$	82,268	$	81,599	$	78,307		$	296,935
	Total interest expense	1,279			2,279		1,184		1,098			5,840
	Net interest income	53,482			79,989		80,415		77,209			291,095
	Provision (recapture) for loan and lease losses	(20		)	288		3,313		(3,682		)	(101		)
	Noninterest income	1,658			6,808		7,622		10,612			26,700
	Noninterest expense	38,049			64,504		64,714		63,619			230,886
	Income before income taxes	17,111			22,005		20,010		27,884			87,010
	Provision for income taxes	4,935			7,414		6,734		7,911			26,994
	Net income	$	12,176		$	14,591	$	13,276	$	19,973		$	60,016
	Per common share (1)
	Earnings (basic)	$	0.31		$	0.28	$	0.26	$	0.39		$	1.24
	Earnings (diluted)	$	0.31		$	0.28	$	0.25	$	0.38		$	1.21
	__________
	(1) Due to averaging of shares, quarterly earnings per share may not add up to the totals reported for the full year.

Summary_of_Significant_Account2

Summary of Significant Accounting Policies (Details) (USD $)	12 Months Ended
	Dec. 31, 2014
	location
Accounting Policies [Line Items]
Net investment in affordable housing program	$7,300,000
Tax credit from affordable housing program	1,500,000
Amortization method qualified affordable housing project investments, amortization	2,000,000
New Accounting Pronouncement or Change in Accounting Principle, Effect of Change on Operating Results	1,100,000
Number Of Branch Locations	154
Number Of Days Used To Determine Treatment As Cash Equivalent	90 days
Number of Days of Delinqunecy at Which Loans Are Categorized As Non Accrual Status	90 days
Loans and Leases Receivable, Nonaccrual Loans Considered Impaired	500,000
Loans and Leases Receivable, Loans Evaluated For Impairment On Quarterly Basis, Outstanding	500,000
Correction of immaterial error, pre-tax increase to interest income on taxable securities	$2,600,000
Core Deposits [Member]
Accounting Policies [Line Items]
Estimated life of CDI, in years	10 years
WASHINGTON
Accounting Policies [Line Items]
Number Of Branch Locations	78
OREGON
Accounting Policies [Line Items]
Number Of Branch Locations	60
IDAHO
Accounting Policies [Line Items]
Number Of Branch Locations	16
Vehicles [Member]
Accounting Policies [Line Items]
Property, Plant and Equipment, Estimated Useful Lives	P5Y
Minimum [Member] | Building and Building Improvements [Member]
Accounting Policies [Line Items]
Property, Plant and Equipment, Estimated Useful Lives	P5Y
Minimum [Member] | Furniture and Fixtures [Member]
Accounting Policies [Line Items]
Property, Plant and Equipment, Estimated Useful Lives	P3Y
Minimum [Member] | Software [Member]
Accounting Policies [Line Items]
Property, Plant and Equipment, Estimated Useful Lives	P3Y
Maximum [Member] | Building and Building Improvements [Member]
Accounting Policies [Line Items]
Property, Plant and Equipment, Estimated Useful Lives	P39Y
Maximum [Member] | Furniture and Fixtures [Member]
Accounting Policies [Line Items]
Property, Plant and Equipment, Estimated Useful Lives	P7Y
Maximum [Member] | Software [Member]
Accounting Policies [Line Items]
Property, Plant and Equipment, Estimated Useful Lives	P5Y

Business_Combinations_Details

Business Combinations (Details) (USD $)	0 Months Ended	12 Months Ended		0 Months Ended	12 Months Ended
	Nov. 01, 2014	Dec. 31, 2014	Dec. 31, 2013	Apr. 02, 2013	Dec. 31, 2012
Intermountain Community Bancorp [Member]
Business Acquisition [Line Items]
Business Combination, Acquisition Related Costs		$4,896,000
Business Acquisition, Pro Forma Revenue		397,152,000	360,655,000
Business Acquisition, Effective Date of Acquisition	1-Nov-14
Business Acquisition, Purchase Price Allocation, Current Assets, Marketable Securities	299,458,000
Business Acquisition, Purchase Price Allocation, Accrued Interest Receivable	4,656,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Property, Plant, and Equipment	20,696,000
Business Combination, Purchase Price Allocation, Amortizable Intangible Assets	10,900,000
Business Combination, Purchase Price Allocation, Other Assets	35,353,000
Business Acquisition, Purchase Price Allocation, Liabilities, Deposits	-736,795,000
Business Acquisition, Purchase Price Allocation, Other Noncurrent Liabilities	-13,725,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net	93,350,000
Business Acquisition, Purchase Price Allocation, FHLB Stock	2,124,000
business combinations, purchase price allocation, loans	502,595,000
Business Combination, Purchase Price Allocation, Goodwill Amount	38,585,000
Business Combination, Cost of Acquired Entity, Purchase Price, Total	131,935,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Cash and Equivalents	47,283,000
Business Acquisition, Purchase Price Allocation, Other Real Estate Owned	2,752,000
Business Acquisition, Purchase Price Allocation, Junior Subordinated Debentures	-22,904,000
Business combination, purchase price allocation, securities sold under agreements to repurchase	-59,043,000
Business Acquisition, Pro Forma Net Income (Loss)		85,939,000	72,587,000
Business Acquisition, Pro Forma Earnings Per Share, Basic		$1.56	$1.32
Business Acquisition, Pro Forma Earnings Per Share, Diluted		$1.55	$1.31
West Coast Bancorp [Member]
Business Acquisition [Line Items]
Business Combination, Acquisition Related Costs		4,536,000	25,488,000		1,780,000
Business Acquisition, Pro Forma Revenue			337,712,000		420,167,000
Business Acquisition, Effective Date of Acquisition				1-Apr-13
Business Combination, Acquired Receivables, Fair Value				1,410,000,000
Business Combination, Purchase Price Allocation, Amortizable Intangible Assets				15,300,000
Business Acquisition, Purchase Price Allocation, Liabilities, Deposits				-1,880,000,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net				312,400,000
Business Combination, Purchase Price Allocation, Goodwill Amount				228,400,000
Business Acquisition, Pro Forma Net Income (Loss)			76,496,000		91,261,000
Business Acquisition, Pro Forma Earnings Per Share, Basic			$1.50		$1.79
Business Acquisition, Pro Forma Earnings Per Share, Diluted			$1.46		$1.74
Compensation and employee benefits [Member] | Intermountain Community Bancorp [Member]
Business Acquisition [Line Items]
Business Combination, Acquisition Related Costs		2,077,000
Compensation and employee benefits [Member] | West Coast Bancorp [Member]
Business Acquisition [Line Items]
Business Combination, Acquisition Related Costs		798,000	8,440,000		0
Occupancy [Member] | Intermountain Community Bancorp [Member]
Business Acquisition [Line Items]
Business Combination, Acquisition Related Costs		44,000
Occupancy [Member] | West Coast Bancorp [Member]
Business Acquisition [Line Items]
Business Combination, Acquisition Related Costs		696,000	4,684,000		0
Advertising and promotion [Member] | Intermountain Community Bancorp [Member]
Business Acquisition [Line Items]
Business Combination, Acquisition Related Costs		464,000
Advertising and promotion [Member] | West Coast Bancorp [Member]
Business Acquisition [Line Items]
Business Combination, Acquisition Related Costs		0	877,000		2,000
Data processing and communications [Member] | Intermountain Community Bancorp [Member]
Business Acquisition [Line Items]
Business Combination, Acquisition Related Costs		0
Data processing and communications [Member] | West Coast Bancorp [Member]
Business Acquisition [Line Items]
Business Combination, Acquisition Related Costs		684,000	767,000		0
Legal and professional fees [Member] | Intermountain Community Bancorp [Member]
Business Acquisition [Line Items]
Business Combination, Acquisition Related Costs		2,114,000
Legal and professional fees [Member] | West Coast Bancorp [Member]
Business Acquisition [Line Items]
Business Combination, Acquisition Related Costs		383,000	4,766,000		1,760,000
Other noninterest expenses [Member] | Intermountain Community Bancorp [Member]
Business Acquisition [Line Items]
Business Combination, Acquisition Related Costs		197,000
Other noninterest expenses [Member] | West Coast Bancorp [Member]
Business Acquisition [Line Items]
Business Combination, Acquisition Related Costs		$1,975,000	$5,954,000		$18,000

Business_Combinations_narrativ

Business Combinations narrative (Details) (USD $)	0 Months Ended	12 Months Ended	0 Months Ended	12 Months Ended
	Nov. 01, 2014	Dec. 31, 2014	Apr. 02, 2013	Dec. 31, 2013	Dec. 31, 2012
Intermountain Community Bancorp [Member]
Business Acquisition [Line Items]
Business Combination, Purchase Price Allocation, Goodwill Amount	$38,585,000
Business Acquisition, Effective Date of Acquisition	1-Nov-14
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net	93,350,000
Business Combination, Purchase Price Allocation, Amortizable Intangible Assets	10,900,000
business combinations, core deposit intangible percentage of core deposits	1.75%
Business Combination, Acquisition Related Costs		4,896,000
Business Combination, Purchase Price Allocation, Other Assets	35,353,000
Business Acquisition, Purchase Price Allocation, Liabilities, Deposits	736,795,000
Business Acquisition, Percentage of Voting Interests Acquired	100.00%
West Coast Bancorp [Member]
Business Acquisition [Line Items]
Business Combination, Purchase Price Allocation, Goodwill Amount			228,400,000
Business Acquisition, Effective Date of Acquisition			1-Apr-13
Business Combination, Acquired Receivables, Fair Value			1,410,000,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net			312,400,000
Business Combination, Purchase Price Allocation, Amortizable Intangible Assets			15,300,000
Business Combination, Acquisition Related Costs		4,536,000		25,488,000	1,780,000
Business Acquisition, Purchase Price Allocation, Liabilities, Deposits			1,880,000,000
Business Combination, Cost of Acquired Entity, Purchase Price, Total			$540,800,000
Business Acquisition, Percentage of Voting Interests Acquired			100.00%

Cash_and_Cash_Equivalents_Deta

Cash and Cash Equivalents (Details) (Federal Reserve Bank [Member], USD $)	Dec. 31, 2014	Dec. 31, 2013
In Millions, unless otherwise specified
Federal Reserve Bank [Member]
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted Cash and Cash Equivalents	$47.40	$36.30

Securities_Securities_Availabl

Securities (Securities Available for Sale) (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$2,087,069	$1,680,491
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	25,527	22,551
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	-14,339	-38,931
Securities available for sale	2,098,257	1,664,111
Available-for-sale Securities, Gross Realized Gain (Loss) [Abstract]
Available-for-sale Securities, Gross Realized Losses	1	170	714
Available-for-sale Securities, Gross Realized Gains	553	632	4,447
U.S. Government Agency and Government-Sponsored Enterprise Mortgage-Backed Securities and Collateralized Mortgage Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	1,160,378	961,442
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	10,219	10,640
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	-8,210	-23,674
Securities available for sale	1,162,387	948,408
State and Municipal Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	483,578	357,013
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	14,432	11,450
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	-1,526	-3,993
Securities available for sale	496,484	364,470
U.S. Government Agency and Government-Sponsored Enterprise Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	416,919	335,671
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	856	434
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	-4,069	-10,066
Securities available for sale	413,706	326,039
US Treasury Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	20,910	21,081
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	0	0
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	-411	-967
Securities available for sale	20,499	20,114
Other Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	5,284	5,284
Available-for-sale Securities, Accumulated Gross Unrealized Gain, before Tax	20	27
Available-for-sale Securities, Accumulated Gross Unrealized Loss, before Tax	-123	-231
Securities available for sale	$5,181	$5,080

Securities_Schedule_of_Contrac

Securities (Schedule of Contractual Maturities of Investment Securities Available for Sale) (Details) (USD $)	Dec. 31, 2014
In Thousands, unless otherwise specified
Available-for-sale Securities [Abstract]
Due within one year, Amortized Cost	$18,872
Due after one year through five years, Amortized Cost	426,532
Due after five years through ten years, Amortized Cost	534,515
Due after ten years, Amortized Cost	1,101,866
Total investment securities available-for-sale, Amortized Cost	2,087,069
Due within one year, Fair Value	19,028
Due after one year through five years, Fair Value	426,035
Due after five years through ten years, Fair Value	537,175
Due after ten years, Fair Value	1,110,838
Available-for-sale Securities, Debt Maturities, without Single Maturity Date, Amortized Cost Basis	5,284
Available-for-sale Securities, Debt Maturities, without Single Maturity Date, Fair Value	5,181
Total investment securities available-for-sale, Fair Value	$2,098,257

Securities_Carrying_Value_of_S

Securities (Carrying Value of Securities Pledged as Collateral) (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Schedule of Available-for-sale Securities [Line Items]
Carrying amount of securities pledged as collateral	$526,643	$362,787
To Washington and Oregon State To Secure Public Deposits [Member]
Schedule of Available-for-sale Securities [Line Items]
Carrying amount of securities pledged as collateral	328,400	277,012
To Federal Reserve Bank To Secure Borrowings [Member]
Schedule of Available-for-sale Securities [Line Items]
Carrying amount of securities pledged as collateral	41,146	42,694
Other Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Carrying amount of securities pledged as collateral	$157,097	$43,081

Securities_Summary_of_Gross_Un

Securities (Summary of Gross Unrealized Losses and Fair Value of the Investments with Unrealized Losses) (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Schedule of Available-for-sale Securities [Line Items]
Less than 12 Months Fair Value	$437,414	$887,693
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Loss, Instant	2,350	23,148
12 Months or More Fair Value	561,668	166,348
12 Months or More Unrealized Losses	-11,989	-15,783
Total Fair Value	999,082	1,054,041
Total Unrealized Losses	-14,339	-38,931
U.S. Government Agency and Government-Sponsored Enterprise Mortgage-Backed Securities and Collateralized Mortgage Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 Months Fair Value	258,825	492,921
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Loss, Instant	1,287	10,991
12 Months or More Fair Value	279,015	121,303
12 Months or More Unrealized Losses	-6,924	-12,684
Total Fair Value	537,840	614,224
Total Unrealized Losses	-8,211	-23,675
State and Municipal Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 Months Fair Value	71,026	112,400
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Loss, Instant	543	3,069
12 Months or More Fair Value	44,148	13,815
12 Months or More Unrealized Losses	-982	-923
Total Fair Value	115,174	126,215
Total Unrealized Losses	-1,525	-3,992
U.S. Government and Government-Sponsored Enterprise Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 Months Fair Value	105,250	260,001
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Loss, Instant	518	8,063
12 Months or More Fair Value	216,221	28,447
12 Months or More Unrealized Losses	-3,551	-2,003
Total Fair Value	321,471	288,448
Total Unrealized Losses	-4,069	-10,066
US Treasury Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 Months Fair Value	0	20,114
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Loss, Instant	0	967
12 Months or More Fair Value	19,450	0
12 Months or More Unrealized Losses	-411	0
Total Fair Value	19,450	20,114
Total Unrealized Losses	-411	-967
Other Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than 12 Months Fair Value	2,313	2,257
Available-for-sale Securities, Continuous Unrealized Loss Position, Less than 12 Months, Aggregate Loss, Instant	2	58
12 Months or More Fair Value	2,834	2,783
12 Months or More Unrealized Losses	-121	-173
Total Fair Value	5,147	5,040
Total Unrealized Losses	($123)	($231)

Securities_Narrative_Details

Securities (Narrative) (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
	issuance
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Gross Realized Gains (Losses), Sale Proceeds	$63,292,000	$166,881,000	$95,165,000
Number Of Issuances Of Securities Exceeding Shareholders Equity Threshold	0
U.S. Government and Government-Sponsored Enterprise Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Number Of Securities In Unrealized Loss Position	34
Number Of Securities In Continuous Loss Position For Twelve Months or More	17
US Treasury Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Number Of Securities In Continuous Loss Position For Twelve Months or More	2
Other Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Issuances Of Securities Exceeding Shareholders Equity Threshold, Percent	10.00%
Number Of Securities In Unrealized Loss Position	2
Number Of Securities In Continuous Loss Position For Twelve Months or More	1
U.S. Government Agency and Government-Sponsored Enterprise Mortgage-Backed Securities and Collateralized Mortgage Obligations [Member]
Schedule of Available-for-sale Securities [Line Items]
Number Of Securities In Unrealized Loss Position	125
Number Of Securities In Continuous Loss Position For Twelve Months or More	43
Municipal Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Number Of Securities In Unrealized Loss Position	95
Number Of Securities In Continuous Loss Position For Twelve Months or More	44
Other than Temporary Impairment Losses, Investments, Portion Recognized in Earnings, Net, Available-for-sale Securities			$3,000,000

Securities_Securities_Summary_

Securities Securities (Summary of Gross Realized Gains and Losses) (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Investments, Debt and Equity Securities [Abstract]
Available-for-sale Securities, Gross Realized Gains	$553	$632	$4,447
Available-for-sale Securities, Gross Realized Losses	-1	-170	-714
Gain (Loss) on Sale of Securities, Net	$552	$462	$3,733

Loans_Narrative_Details

Loans (Narrative) (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
	contract	contract	contract
	loan	loan
Financing Receivable, Recorded Investment [Line Items]
Loans to related parties	$13,200,000	$14,200,000
Loans and Leases Receivable, Related Parties, Additions	5,700,000
Repayments on related party loans	6,700,000
Commercial and residential real estate loans pledged as FHLB collateral	1,083,879,000	1,075,389,000
Federal Reserve Bank, Advances, Collateral Pledged	86,130,000	85,452,000
Financing Receivable, Recorded Investment, Nonaccrual Status	31,352,000
Loans and Leases Receivable, Impaired, Interest Lost on Nonaccrual Loans	2,200,000	2,900,000	3,400,000
Financing Receivable, Recorded Investment, 90 Days Past Due and Still Accruing, Number of Loans	1,400,000
Financing Receivable, Recorded Investment, 90 Days Past Due and Still Accruing, Number of Loans		0
Loans and Leases Receivable, Nonaccrual of Interest, Commitments of Additional Funds	349,000	28,000
Financing Receivable Modifications Additional Commitment To Lend	0	0
Financing Receivable, Modifications, Subsequent Default, Number of Contracts	0	0	0
Loans Receivable [Member]
Financing Receivable, Recorded Investment [Line Items]
Commercial and residential real estate loans pledged as FHLB collateral	$1,083,879,000	$1,075,389,000

Loans_Analysis_of_Loan_Portfol

Loans (Analysis of Loan Portfolio by Major Types of Loans) (Details) (USD $)	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012	Dec. 31, 2011
In Thousands, unless otherwise specified
Financing Receivable, Recorded Investment [Line Items]
Less: Net unearned income	($59,374)		($68,282)
Total loans, net of unearned income	5,445,378	[1]	4,517,296	[1]
Less: Allowance for loan and lease losses	-69,569		-72,454		-82,300	-57,985
Loans, net	5,375,809		4,444,842
Loans held for sale	1,116		735
One-to-Four Family Residential [Member]
Financing Receivable, Recorded Investment [Line Items]
Real Estate	202,564		142,260
Real Estate Construction	120,887		67,468
Less: Allowance for loan and lease losses	-2,281		-1,252		-694	-654
Commercial and Multifamily Residential [Member]
Financing Receivable, Recorded Investment [Line Items]
Real Estate	2,492,310		2,234,266
Real Estate Construction	136,764		131,763
Commercial Portfolio Segment [Member]
Financing Receivable, Recorded Investment [Line Items]
Commercial Business	2,164,070		1,622,724
Real Estate Portfolio Segment [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Real Estate	2,694,874		2,376,526
Real Estate Construction Portfolio Segment [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Real Estate Construction	257,651		199,231
Consumer Portfolio Segment [Member]
Financing Receivable, Recorded Investment [Line Items]
Consumer	388,157		387,097
Less: Allowance for loan and lease losses	-3,180		-2,547		-2,437	-2,719
Loans, Excluding Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Less: Net unearned income	-59,374		-68,282
Total loans, net of unearned income	5,214,794		4,219,451
Less: Allowance for loan and lease losses	-53,233		-52,280
Loans, net	5,161,561		4,167,171
Loans held for sale	1,116		735
Loans, Excluding Purchased Credit Impaired Loans [Member] | One-to-Four Family Residential [Member]
Financing Receivable, Recorded Investment [Line Items]
Real Estate	175,571		108,317
Real Estate Construction	116,866		54,155
Loans, Excluding Purchased Credit Impaired Loans [Member] | Commercial and Multifamily Residential [Member]
Financing Receivable, Recorded Investment [Line Items]
Real Estate	2,363,541		2,080,075
Real Estate Construction	134,443		126,390
Loans, Excluding Purchased Credit Impaired Loans [Member] | Commercial Portfolio Segment [Member]
Financing Receivable, Recorded Investment [Line Items]
Commercial Business	2,119,565		1,561,782
Loans, Excluding Purchased Credit Impaired Loans [Member] | Real Estate Portfolio Segment [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Real Estate			2,188,392
Loans, Excluding Purchased Credit Impaired Loans [Member] | Real Estate Construction Portfolio Segment [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Real Estate Construction	251,309		180,545
Loans, Excluding Purchased Credit Impaired Loans [Member] | Consumer Portfolio Segment [Member]
Financing Receivable, Recorded Investment [Line Items]
Consumer	364,182		357,014
Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Less: Net unearned income	0		0
Total loans, net of unearned income	230,584		297,845
Less: Allowance for loan and lease losses	-16,336		-20,174
Loans, net	214,248		277,671
Loans held for sale	0		0
Purchased Credit Impaired Loans [Member] | One-to-Four Family Residential [Member]
Financing Receivable, Recorded Investment [Line Items]
Real Estate	26,993		33,943
Real Estate Construction	4,021		13,313
Purchased Credit Impaired Loans [Member] | Commercial and Multifamily Residential [Member]
Financing Receivable, Recorded Investment [Line Items]
Real Estate	128,769		154,191
Real Estate Construction	2,321		5,373
Purchased Credit Impaired Loans [Member] | Commercial Portfolio Segment [Member]
Financing Receivable, Recorded Investment [Line Items]
Commercial Business	44,505		60,942
Purchased Credit Impaired Loans [Member] | Real Estate Portfolio Segment [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Real Estate			188,134
Purchased Credit Impaired Loans [Member] | Real Estate Construction Portfolio Segment [Member]
Financing Receivable, Recorded Investment [Line Items]
Total Real Estate Construction	6,342		18,686
Purchased Credit Impaired Loans [Member] | Consumer Portfolio Segment [Member]
Financing Receivable, Recorded Investment [Line Items]
Consumer	$23,975		$30,083
[1]	(1) Reclassified to conform to the current period’s presentation. The reclassification was limited to removing the separate line items for covered loans and including the prior period balances in the line items for loans, net of unearned income and allowance for loan and lease losses.

Loans_Analysis_of_Nonaccrual_L

Loans (Analysis of Nonaccrual Loans) (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Recorded Investment, Nonaccrual Status	$31,352
Unpaid Principal Balance Nonaccrual Loans	44,774	52,434
Recorded Investment Nonaccrual Loans		34,015
Consumer Portfolio Segment [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Recorded Investment, Nonaccrual Status	2,939
Unpaid Principal Balance Nonaccrual Loans	3,930	6,187
Recorded Investment Nonaccrual Loans		3,991
Secured Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Recorded Investment, Nonaccrual Status	16,552
Unpaid Principal Balance Nonaccrual Loans	21,453	19,186
Recorded Investment Nonaccrual Loans		12,433
Unsecured Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Recorded Investment, Nonaccrual Status	247
Unpaid Principal Balance Nonaccrual Loans	269	202
Recorded Investment Nonaccrual Loans		176
One-to-Four Family Residential [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Recorded Investment, Nonaccrual Status	2,822
Unpaid Principal Balance Nonaccrual Loans	5,680	4,678
Recorded Investment Nonaccrual Loans		2,667
Commercial Land [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Recorded Investment, Nonaccrual Status	821
Unpaid Principal Balance Nonaccrual Loans	1,113	783
Recorded Investment Nonaccrual Loans		442
Income Property Multifamily [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Recorded Investment, Nonaccrual Status	3,200
Unpaid Principal Balance Nonaccrual Loans	5,521	5,383
Recorded Investment Nonaccrual Loans		4,267
Owner Occupied [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Recorded Investment, Nonaccrual Status	3,826
Unpaid Principal Balance Nonaccrual Loans	5,837	7,486
Recorded Investment Nonaccrual Loans		6,334
Land And Acquisition [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Recorded Investment, Nonaccrual Status	95
Unpaid Principal Balance Nonaccrual Loans	112	6,601
Recorded Investment Nonaccrual Loans		3,246
Residential Construction [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Recorded Investment, Nonaccrual Status	370
Unpaid Principal Balance Nonaccrual Loans	370	1,928
Recorded Investment Nonaccrual Loans		459
Owner Occupied Construction [Member]
Financing Receivable, Recorded Investment [Line Items]
Financing Receivable, Recorded Investment, Nonaccrual Status	480
Unpaid Principal Balance Nonaccrual Loans	489	0
Recorded Investment Nonaccrual Loans		$0

Loans_Analysis_of_the_Aged_Loa

Loans (Analysis of the Aged Loan Portfolio) (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonaccrual Loans	$31,352
Consumer Portfolio Segment [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonaccrual Loans	2,939
Secured Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonaccrual Loans	16,552
Unsecured Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonaccrual Loans	247
One-to-Four Family Residential [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonaccrual Loans	2,822
Commercial Land [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonaccrual Loans	821
Owner Occupied [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonaccrual Loans	3,826
Land And Acquisition [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonaccrual Loans	95
Residential Construction [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonaccrual Loans	370
Income Property Multifamily [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonaccrual Loans	3,200
Owner Occupied Construction [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Nonaccrual Loans	480
Loans, Excluding Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current Loans	5,158,985	4,158,873
30 - 59 Days Past Due	14,656	20,754
60 - 89 Days Past Due	8,415	5,809
Financing Receivable, Recorded Investment, Equal to Greater than 90 Days Past Due	1,386	0
Total Past Due	24,457	26,563
Nonaccrual Loans	31,352	34,015
Loans Receivable, Net	5,214,794	4,219,451
Loans, Excluding Purchased Credit Impaired Loans [Member] | Income Property Multifamily Construction [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current Loans	73,783	86,521
30 - 59 Days Past Due	0	0
60 - 89 Days Past Due	0	0
Financing Receivable, Recorded Investment, Equal to Greater than 90 Days Past Due	0
Total Past Due	0	0
Nonaccrual Loans	0	0
Loans Receivable, Net	73,783	86,521
Loans, Excluding Purchased Credit Impaired Loans [Member] | Consumer Portfolio Segment [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current Loans	341,032	322,685
30 - 59 Days Past Due	933	835
60 - 89 Days Past Due	118	823
Financing Receivable, Recorded Investment, Equal to Greater than 90 Days Past Due	10	0
Total Past Due	1,061	1,658
Nonaccrual Loans	2,939	3,991
Loans Receivable, Net	345,032	328,334
Loans, Excluding Purchased Credit Impaired Loans [Member] | Secured Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current Loans	2,004,418	1,457,820
30 - 59 Days Past Due	5,137	12,713
60 - 89 Days Past Due	6,149	681
Financing Receivable, Recorded Investment, Equal to Greater than 90 Days Past Due	1,372	0
Total Past Due	12,658	13,394
Nonaccrual Loans	16,552	12,433
Loans Receivable, Net	2,033,628	1,483,647
Loans, Excluding Purchased Credit Impaired Loans [Member] | Unsecured Loans [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current Loans	79,661	72,255
30 - 59 Days Past Due	185	156
60 - 89 Days Past Due	0	17
Financing Receivable, Recorded Investment, Equal to Greater than 90 Days Past Due	0	0
Total Past Due	185	173
Nonaccrual Loans	247	176
Loans Receivable, Net	80,093	72,604
Loans, Excluding Purchased Credit Impaired Loans [Member] | One-to-Four Family Residential [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current Loans	167,197	100,591
30 - 59 Days Past Due	1,700	1,993
60 - 89 Days Past Due	45	641
Financing Receivable, Recorded Investment, Equal to Greater than 90 Days Past Due	0	0
Total Past Due	1,745	2,634
Nonaccrual Loans	2,822	2,667
Loans Receivable, Net	171,764	105,892
Loans, Excluding Purchased Credit Impaired Loans [Member] | Commercial Land [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current Loans	187,470	142,034
30 - 59 Days Past Due	1,454	0
60 - 89 Days Past Due	34	358
Financing Receivable, Recorded Investment, Equal to Greater than 90 Days Past Due	0	0
Total Past Due	1,488	358
Nonaccrual Loans	821	442
Loans Receivable, Net	189,779	142,834
Loans, Excluding Purchased Credit Impaired Loans [Member] | Owner Occupied [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current Loans	839,689	749,561
30 - 59 Days Past Due	937	4,714
60 - 89 Days Past Due	289	0
Financing Receivable, Recorded Investment, Equal to Greater than 90 Days Past Due	0	0
Total Past Due	1,226	4,714
Nonaccrual Loans	3,826	6,334
Loans Receivable, Net	844,741	760,609
Loans, Excluding Purchased Credit Impaired Loans [Member] | Land And Acquisition [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current Loans	15,462	8,225
30 - 59 Days Past Due	953	199
60 - 89 Days Past Due	0	0
Financing Receivable, Recorded Investment, Equal to Greater than 90 Days Past Due	0	0
Total Past Due	953	199
Nonaccrual Loans	95	3,246
Loans Receivable, Net	16,510	11,670
Loans, Excluding Purchased Credit Impaired Loans [Member] | Residential Construction [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current Loans	97,821	41,533
30 - 59 Days Past Due	326	0
60 - 89 Days Past Due	0	0
Financing Receivable, Recorded Investment, Equal to Greater than 90 Days Past Due	4	0
Total Past Due	330	0
Nonaccrual Loans	370	459
Loans Receivable, Net	98,521	41,992
Loans, Excluding Purchased Credit Impaired Loans [Member] | Income Property Multifamily [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current Loans	1,294,982	1,138,732
30 - 59 Days Past Due	3,031	144
60 - 89 Days Past Due	786	3,289
Financing Receivable, Recorded Investment, Equal to Greater than 90 Days Past Due	0	0
Total Past Due	3,817	3,433
Nonaccrual Loans	3,200	4,267
Loans Receivable, Net	1,301,999	1,146,432
Loans, Excluding Purchased Credit Impaired Loans [Member] | Owner Occupied Construction [Member]
Financing Receivable, Recorded Investment, Past Due [Line Items]
Current Loans	57,470	38,916
30 - 59 Days Past Due	0	0
60 - 89 Days Past Due	994	0
Financing Receivable, Recorded Investment, Equal to Greater than 90 Days Past Due	0
Total Past Due	994	0
Nonaccrual Loans	480	0
Loans Receivable, Net	$58,944	$38,916

Loans_Analysis_of_Impaired_Loa

Loans (Analysis of Impaired Loans) (Details) (Loans, Excluding Purchased Credit Impaired Loans [Member], USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Recorded Investment of Loans Collectively Measured for Contingency Provision	$5,186,695	$4,193,062
Recorded Investment of Loans Individually Measured for Specific Impairment	28,099	26,389
Recorded Investment	0	23
Unpaid Principal Balance	0	27
Related Allowance	0	4
Impaired Financing Receivable, Average Recorded Investment	26,635	32,039	47,524
Impaired Financing Receivable, Interest Income, Accrual Method	1,327	1,306	1,114
Income Property Multifamily Construction [Member]
Recorded Investment of Loans Collectively Measured for Contingency Provision	73,783	86,521
Recorded Investment of Loans Individually Measured for Specific Impairment	0	0
Recorded Investment	0	0
Unpaid Principal Balance	0	0
Related Allowance	0	0
Impaired Financing Receivable, Average Recorded Investment	0	0	3,169
Impaired Financing Receivable, Interest Income, Accrual Method	0	0	0
Consumer Portfolio Segment [Member]
Recorded Investment of Loans Collectively Measured for Contingency Provision	344,908	328,167
Recorded Investment of Loans Individually Measured for Specific Impairment	124	167
Impaired Financing Receivable, Average Recorded Investment	147	253	1,112
Impaired Financing Receivable, Interest Income, Accrual Method	9	6	7
Land And Acquisition [Member]
Recorded Investment of Loans Collectively Measured for Contingency Provision	16,401	9,726
Recorded Investment of Loans Individually Measured for Specific Impairment	109	1,944
Recorded Investment	109	113
Unpaid Principal Balance	109	113
Related Allowance	67	71
Impaired Financing Receivable, Average Recorded Investment	694	2,624	4,465
Impaired Financing Receivable, Interest Income, Accrual Method	6	6	0
Residential Construction [Member]
Recorded Investment of Loans Collectively Measured for Contingency Provision	98,521	41,992
Recorded Investment of Loans Individually Measured for Specific Impairment	0	0
Recorded Investment	0	0
Unpaid Principal Balance	0	0
Related Allowance	0	0
Impaired Financing Receivable, Average Recorded Investment	0	420	3,223
Impaired Financing Receivable, Interest Income, Accrual Method	0	0	11
Commercial Land [Member]
Recorded Investment of Loans Collectively Measured for Contingency Provision	189,779	142,719
Recorded Investment of Loans Individually Measured for Specific Impairment	0	115
Recorded Investment	0	0
Unpaid Principal Balance	0	0
Related Allowance	0	0
Impaired Financing Receivable, Average Recorded Investment	82	1,691	3,124
Impaired Financing Receivable, Interest Income, Accrual Method	0	0	0
Income Property Multifamily [Member]
Recorded Investment of Loans Collectively Measured for Contingency Provision	1,295,650	1,140,019
Recorded Investment of Loans Individually Measured for Specific Impairment	6,349	6,413
Recorded Investment	0	918
Unpaid Principal Balance	0	933
Related Allowance	0	26
Impaired Financing Receivable, Average Recorded Investment	6,782	8,910	7,895
Impaired Financing Receivable, Interest Income, Accrual Method	270	238	77
Owner Occupied [Member]
Recorded Investment of Loans Collectively Measured for Contingency Provision	835,895	749,601
Recorded Investment of Loans Individually Measured for Specific Impairment	8,846	11,008
Recorded Investment	582	3,802
Unpaid Principal Balance	582	3,817
Related Allowance	27	1,073
Impaired Financing Receivable, Average Recorded Investment	9,472	10,779	13,315
Impaired Financing Receivable, Interest Income, Accrual Method	956	971	1,004
Owner Occupied Construction [Member]
Recorded Investment of Loans Collectively Measured for Contingency Provision	58,944	38,916
Recorded Investment of Loans Individually Measured for Specific Impairment	0	0
Recorded Investment	0	0
Unpaid Principal Balance	0	0
Related Allowance	0	0
One-to-Four Family Residential [Member]
Recorded Investment of Loans Collectively Measured for Contingency Provision	169,619	104,272
Recorded Investment of Loans Individually Measured for Specific Impairment	2,145	1,620
Recorded Investment	424	442
Unpaid Principal Balance	465	479
Related Allowance	120	138
Impaired Financing Receivable, Average Recorded Investment	2,094	1,665	2,130
Impaired Financing Receivable, Interest Income, Accrual Method	49	63	0
Secured Loans [Member]
Recorded Investment of Loans Collectively Measured for Contingency Provision	2,023,104	1,478,560
Recorded Investment of Loans Individually Measured for Specific Impairment	10,524	5,087
Recorded Investment	99	2,866
Unpaid Principal Balance	99	2,885
Related Allowance	25	343
Impaired Financing Receivable, Average Recorded Investment	7,345	5,636	8,978
Impaired Financing Receivable, Interest Income, Accrual Method	36	19	9
Unsecured Loans [Member]
Recorded Investment of Loans Collectively Measured for Contingency Provision	80,091	72,569
Recorded Investment of Loans Individually Measured for Specific Impairment	2	35
Recorded Investment	2	35
Unpaid Principal Balance	2	35
Related Allowance	2	35
Impaired Financing Receivable, Average Recorded Investment	19	61	113
Impaired Financing Receivable, Interest Income, Accrual Method	1	3	6
Impaired Loans Without Recorded Allowance [Member]
Recorded Investment	26,883	18,190
Unpaid Principal Balance	38,433	26,223
Impaired Loans With Recorded Allowance [Member]
Recorded Investment	1,216	8,199
Unpaid Principal Balance	1,257	8,289
Related Allowance	241	1,690
Impaired Loans Without Recorded Allowance [Member]
Recorded Investment	124	144
Unpaid Principal Balance	201	210
Impaired Loans Without Recorded Allowance [Member] | Income Property Multifamily Construction [Member]
Recorded Investment	0	0
Unpaid Principal Balance	0	0
Impaired Loans Without Recorded Allowance [Member] | Land And Acquisition [Member]
Recorded Investment	0	1,831
Unpaid Principal Balance	0	2,587
Impaired Loans Without Recorded Allowance [Member] | Residential Construction [Member]
Recorded Investment	0	0
Unpaid Principal Balance	0	0
Impaired Loans Without Recorded Allowance [Member] | Commercial Land [Member]
Recorded Investment	0	115
Unpaid Principal Balance	0	398
Impaired Loans Without Recorded Allowance [Member] | Income Property Multifamily [Member]
Recorded Investment	6,349	5,495
Unpaid Principal Balance	10,720	7,885
Impaired Loans Without Recorded Allowance [Member] | Owner Occupied [Member]
Recorded Investment	8,264	7,206
Unpaid Principal Balance	12,732	10,464
Impaired Loans Without Recorded Allowance [Member] | Owner Occupied Construction [Member]
Recorded Investment	0	0
Unpaid Principal Balance	0	0
Impaired Loans Without Recorded Allowance [Member] | One-to-Four Family Residential [Member]
Recorded Investment	1,721	1,178
Unpaid Principal Balance	2,370	2,119
Impaired Loans Without Recorded Allowance [Member] | Secured Loans [Member]
Recorded Investment	10,425	2,221
Unpaid Principal Balance	12,410	2,560
Impaired Loans Without Recorded Allowance [Member] | Unsecured Loans [Member]
Recorded Investment	0	0
Unpaid Principal Balance	$0	$0

Loans_Loans_Analysis_of_Troubl

Loans Loans (Analysis of Troubled Debt Restructurings) (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
	contract	contract	contract
Financing Receivable, Modifications [Line Items]
Financing Receivable Modifications Additional Commitment To Lend	$0	$0
Financing Receivable, Modifications, Subsequent Default, Number of Contracts	0	0	0
FHLB Advances, Collateral Pledged	1,083,879	1,075,389
Loans, Excluding Purchased Credit Impaired Loans [Member]
Financing Receivable, Modifications [Line Items]
Financing Receivable, Modifications, Number of Contracts	8	12	2
Pre-Modification Outstanding Recorded Investment	2,892	1,968	4,474
Post-Modification Outstanding Recorded Investment	2,875	1,968	2,844
Loans, Excluding Purchased Credit Impaired Loans [Member] | Secured Loans [Member]
Financing Receivable, Modifications [Line Items]
Financing Receivable, Modifications, Number of Contracts	4	2	1
Pre-Modification Outstanding Recorded Investment	759	190	195
Post-Modification Outstanding Recorded Investment	759	190	194
Loans, Excluding Purchased Credit Impaired Loans [Member] | One-to-Four Family Residential [Member]
Financing Receivable, Modifications [Line Items]
Financing Receivable, Modifications, Number of Contracts	2	1	0
Pre-Modification Outstanding Recorded Investment	494	113	0
Post-Modification Outstanding Recorded Investment	494	113	0
Loans, Excluding Purchased Credit Impaired Loans [Member] | Commercial Land [Member]
Financing Receivable, Modifications [Line Items]
Financing Receivable, Modifications, Number of Contracts	0	1	0
Pre-Modification Outstanding Recorded Investment	0	137	0
Post-Modification Outstanding Recorded Investment	0	137	0
Loans, Excluding Purchased Credit Impaired Loans [Member] | Income Property Multifamily [Member]
Financing Receivable, Modifications [Line Items]
Financing Receivable, Modifications, Number of Contracts	1	4	1
Pre-Modification Outstanding Recorded Investment	143	1,186	4,279
Post-Modification Outstanding Recorded Investment	126	1,186	2,650
Loans, Excluding Purchased Credit Impaired Loans [Member] | Owner Occupied [Member]
Financing Receivable, Modifications [Line Items]
Financing Receivable, Modifications, Number of Contracts	1	1	0
Pre-Modification Outstanding Recorded Investment	1,496	172	0
Post-Modification Outstanding Recorded Investment	1,496	172	0
Loans, Excluding Purchased Credit Impaired Loans [Member] | Land And Acquisition [Member]
Financing Receivable, Modifications [Line Items]
Financing Receivable, Modifications, Number of Contracts	0	1	0
Pre-Modification Outstanding Recorded Investment	0	117	0
Post-Modification Outstanding Recorded Investment	0	117	0
Loans, Excluding Purchased Credit Impaired Loans [Member] | Consumer Portfolio Segment [Member]
Financing Receivable, Modifications [Line Items]
Financing Receivable, Modifications, Number of Contracts	0	2	0
Pre-Modification Outstanding Recorded Investment	0	53	0
Post-Modification Outstanding Recorded Investment	$0	$53	0

Loans_Loans_analysis_of_purcha

Loans Loans, analysis of purchased credit impaired loans (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
In Thousands, unless otherwise specified
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Allowance	$69,569	$72,454	$82,300	$57,985
Loans and Leases Receivable, Net Amount	5,375,809	4,444,842
One-to-Four Family Residential [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Allowance	2,281	1,252	694	654
Consumer Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Allowance	3,180	2,547	2,437	2,719
Purchased Credit Impaired Loans [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	256,468	341,142
Valuation discount resulting from acquisition accounting	25,884	43,297
Loans and Leases Receivable, Allowance	16,336	20,174
Loans and Leases Receivable, Net Amount	214,248	277,671
Purchased Credit Impaired Loans [Member] | Commercial Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	50,334	72,870
Purchased Credit Impaired Loans [Member] | One-to-Four Family Residential [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	31,981	41,642
Purchased Credit Impaired Loans [Member] | Commercial and Multifamily Residential [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	140,398	170,879
Purchased Credit Impaired Loans [Member] | Real Estate Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	172,379	212,521
Purchased Credit Impaired Loans [Member] | One-to-Four Family Residential Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	4,353	14,781
Purchased Credit Impaired Loans [Member] | Commercial and Multifamily Residential Construction [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	2,588	6,869
Purchased Credit Impaired Loans [Member] | Real Estate Construction Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	6,941	21,650
Purchased Credit Impaired Loans [Member] | Consumer Portfolio Segment [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	$26,814	$34,101

Recovered_Sheet1

Loans Loans (Analysis of Purchased Credit Impaired - Accretable Yield Rollforward) (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Loans, Analysis of Purchased Credit Impaired Loans, Accretable Yield Rollforward [Abstract]
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Accretable Yield	$73,849	$103,907	$166,888	$259,669
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Accretable Yield, Accretion	-36,066	-51,816	-86,671
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Accretable Yield, Disposals of Loans	3,386	6,898	12,856
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Accretable Yield, Reclassifications from Nonaccretable Difference	$9,394	($4,267)	$6,746

Allowance_for_Loan_and_Lease_L2

Allowance for Loan and Lease Losses and Unfunded Commitments and Letters of Credit (Narrative) (Details) (Maximum [Member])	12 Months Ended
	Dec. 31, 2014
Maximum [Member]
Accounts, Notes, Loans and Financing Receivable [Line Items]
Percentage of unallocated loan amount	5.00%

Allowance_for_Loan_and_Lease_L3

Allowance for Loan and Lease Losses and Unfunded Commitments and Letters of Credit (Allowance for Noncovered Loan and Lease Losses) (Details) (USD $)	3 Months Ended								12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of year				$72,454				$82,300	$72,454	$82,300	$57,985
Charge-offs									-24,722	-23,941	-25,541
Recoveries									15,110	14,196	10,489
Provision (recapture) for loan and lease losses	1,708	980	2,117	1,922	-3,682	3,313	288	-20	6,727	-101	39,367
Balance at the end of year	69,569				72,454				69,569	72,454	82,300
Specific Reserve	241				1,690				241	1,690	1,395
General Allocation	69,328				70,764				69,328	70,764	80,905
Consumer Portfolio Segment [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of year				2,547				2,437	2,547	2,437	2,719
Charge-offs									-2,774	-2,242	-2,534
Recoveries									1,353	552	1,171
Provision (recapture) for loan and lease losses									2,054	1,800	1,081
Balance at the end of year	3,180				2,547				3,180	2,547	2,437
Specific Reserve	0				4				0	4	0
General Allocation	3,180				2,543				3,180	2,543	2,437
Purchased Credit Impaired Loans [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of year				20,174				30,056	20,174	30,056	4,944
Charge-offs									-14,436	-13,853	-5,112
Recoveries									7,721	7,232	4,332
Provision (recapture) for loan and lease losses									2,877	-3,261	25,892
Balance at the end of year	16,336				20,174				16,336	20,174	30,056
Specific Reserve	0				0				0	0	0
General Allocation	16,336				20,174				16,336	20,174	30,056
Unallocated Financing Receivables [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of year				1,655				1,011	1,655	1,011	694
Charge-offs									0	0	0
Recoveries									0	0	0
Provision (recapture) for loan and lease losses									189	644	317
Balance at the end of year	1,844				1,655				1,844	1,655	1,011
Specific Reserve	0				0				0	0	0
General Allocation	1,844				1,655				1,844	1,655	1,011
Secured Loans [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of year				31,027				27,270	31,027	27,270	24,745
Charge-offs									-4,159	-4,148	-10,029
Recoveries									2,637	1,512	1,354
Provision (recapture) for loan and lease losses									-3,582	6,393	11,200
Balance at the end of year	25,923				31,027				25,923	31,027	27,270
Specific Reserve	25				343				25	343	113
General Allocation	25,898				30,684				25,898	30,684	27,157
Unsecured Loans [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of year				696				753	696	753	689
Charge-offs									-130	-794	-144
Recoveries									370	932	194
Provision (recapture) for loan and lease losses									-9	-195	14
Balance at the end of year	927				696				927	696	753
Specific Reserve	2				35				2	35	92
General Allocation	925				661				925	661	661
One-to-Four Family Residential [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of year				1,252				694	1,252	694	654
Charge-offs									-230	-228	-549
Recoveries									159	270	285
Provision (recapture) for loan and lease losses									1,100	516	304
Balance at the end of year	2,281				1,252				2,281	1,252	694
Specific Reserve	120				138				120	138	112
General Allocation	2,161				1,114				2,161	1,114	582
Commercial Land [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of year				489				460	489	460	488
Charge-offs									-29	-20	-526
Recoveries									70	169	63
Provision (recapture) for loan and lease losses									269	-120	435
Balance at the end of year	799				489				799	489	460
Specific Reserve	0				0				0	0	0
General Allocation	799				489				799	489	460
Income Property Multifamily [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of year				9,234				11,033	9,234	11,033	9,551
Charge-offs									-1,934	-1,405	-4,030
Recoveries									819	489	905
Provision (recapture) for loan and lease losses									1,040	-883	4,607
Balance at the end of year	9,159				9,234				9,159	9,234	11,033
Specific Reserve	0				26				0	26	1,040
General Allocation	9,159				9,208				9,159	9,208	9,993
Owner Occupied [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of year				3,605				6,362	3,605	6,362	9,606
Charge-offs									-1,030	-1,118	-918
Recoveries									51	375	631
Provision (recapture) for loan and lease losses									2,381	-2,014	-2,957
Balance at the end of year	5,007				3,605				5,007	3,605	6,362
Specific Reserve	27				1,073				27	1,073	38
General Allocation	4,980				2,532				4,980	2,532	6,324
Land And Acquisition [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of year				610				1,171	610	1,171	2,331
Charge-offs									0	-32	-989
Recoveries									740	2,553	1,059
Provision (recapture) for loan and lease losses									-153	-3,082	-1,230
Balance at the end of year	1,197				610				1,197	610	1,171
Specific Reserve	67				71				67	71	0
General Allocation	1,130				539				1,130	539	1,171
Residential Construction [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of year				822				635	822	635	864
Charge-offs									0	-101	-617
Recoveries									1,190	112	429
Provision (recapture) for loan and lease losses									-152	176	-41
Balance at the end of year	1,860				822				1,860	822	635
Specific Reserve	0				0				0	0	0
General Allocation	1,860				822				1,860	822	635
Income Property Multifamily Construction [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of year				285				316	285	316	665
Charge-offs									0	0	-93
Recoveries									0	0	66
Provision (recapture) for loan and lease losses									337	-31	-322
Balance at the end of year	622				285				622	285	316
Specific Reserve	0				0				0	0	0
General Allocation	622				285				622	285	316
Owner Occupied Construction [Member]
Allowance for Loan and Lease Losses [Roll Forward]
Balance at beginning of year				58				102	58	102	35
Charge-offs									0	0	0
Recoveries									0	0	0
Provision (recapture) for loan and lease losses									376	-44	67
Balance at the end of year	434				58				434	58	102
Specific Reserve	0				0				0	0	0
General Allocation	$434				$58				$434	$58	$102

Allowance_for_Loan_and_Lease_L4

Allowance for Loan and Lease Losses and Unfunded Commitments and Letters of Credit (Changes in the Allowance for Unfunded Commitments and Letters of Credit) (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Allowance For Loan And Lease Losses And Unfunded Loan Commitments And Letters Of Credit
Beginning balance	$2,505	$1,915	$1,535
Net changes in the allowance for unfunded commitments and letters of credit	150	590	380
Ending balance	$2,655	$2,505	$1,915

Allowance_for_Loan_and_Lease_L5

Allowance for Loan and Lease Losses and Unfunded Commitments and Letters of Credit (Analysis of Credit Quality of Loan Portfolio) (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
In Thousands, unless otherwise specified
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Allowance	$69,569	$72,454	$82,300	$57,985
Loans, net	5,375,809	4,444,842
Loans, Excluding Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	5,214,794	4,219,451
Loans and Leases Receivable, Allowance	53,233	52,280
Loans, net	5,161,561	4,167,171
Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	256,468	341,142
Valuation discount resulting from acquisition accounting	25,884	43,297
Loans and Leases Receivable, Allowance	16,336	20,174
Loans, net	214,248	277,671
Pass [Member] | Loans, Excluding Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	5,086,653	4,027,764
Pass [Member] | Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	216,807	264,008
Special Mention [Member] | Loans, Excluding Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	34,967	53,231
Special Mention [Member] | Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	3,175	12,118
Substandard [Member] | Loans, Excluding Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	93,174	137,989
Substandard [Member] | Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	36,486	64,989
Doubtful [Member] | Loans, Excluding Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	0	467
Doubtful [Member] | Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	0	27
Unlikely to be Collected Financing Receivable [Member] | Loans, Excluding Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	0	0
Unlikely to be Collected Financing Receivable [Member] | Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	0	0
Commercial Portfolio Segment [Member] | Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	50,334	72,870
Secured Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Allowance	25,923	31,027	27,270	24,745
Secured Loans [Member] | Loans, Excluding Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	2,033,628	1,483,647
Secured Loans [Member] | Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	48,087	69,650
Secured Loans [Member] | Pass [Member] | Loans, Excluding Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	1,963,210	1,372,038
Secured Loans [Member] | Pass [Member] | Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	37,927	48,510
Secured Loans [Member] | Special Mention [Member] | Loans, Excluding Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	15,790	43,309
Secured Loans [Member] | Special Mention [Member] | Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	937	2,849
Secured Loans [Member] | Substandard [Member] | Loans, Excluding Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	54,628	68,300
Secured Loans [Member] | Substandard [Member] | Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	9,223	18,291
Secured Loans [Member] | Doubtful [Member] | Loans, Excluding Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	0	0
Secured Loans [Member] | Doubtful [Member] | Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	0	0
Secured Loans [Member] | Unlikely to be Collected Financing Receivable [Member] | Loans, Excluding Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	0	0
Secured Loans [Member] | Unlikely to be Collected Financing Receivable [Member] | Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	0	0
Unsecured Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Allowance	927	696	753	689
Unsecured Loans [Member] | Loans, Excluding Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	80,093	72,604
Unsecured Loans [Member] | Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	2,247	3,220
Unsecured Loans [Member] | Pass [Member] | Loans, Excluding Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	79,534	72,226
Unsecured Loans [Member] | Pass [Member] | Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	2,156	2,732
Unsecured Loans [Member] | Special Mention [Member] | Loans, Excluding Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	0	199
Unsecured Loans [Member] | Special Mention [Member] | Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	0	396
Unsecured Loans [Member] | Substandard [Member] | Loans, Excluding Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	559	179
Unsecured Loans [Member] | Substandard [Member] | Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	91	92
Unsecured Loans [Member] | Doubtful [Member] | Loans, Excluding Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	0	0
Unsecured Loans [Member] | Doubtful [Member] | Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	0	0
Unsecured Loans [Member] | Unlikely to be Collected Financing Receivable [Member] | Loans, Excluding Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	0	0
Unsecured Loans [Member] | Unlikely to be Collected Financing Receivable [Member] | Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	0	0
Real Estate Portfolio Segment [Member] | Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	172,379	212,521
One-to-Four Family Residential [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Allowance	2,281	1,252	694	654
One-to-Four Family Residential [Member] | Loans, Excluding Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	171,764	105,892
One-to-Four Family Residential [Member] | Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	31,981	41,642
One-to-Four Family Residential [Member] | Pass [Member] | Loans, Excluding Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	163,914	98,626
One-to-Four Family Residential [Member] | Pass [Member] | Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	28,822	35,066
One-to-Four Family Residential [Member] | Special Mention [Member] | Loans, Excluding Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	55	1,567
One-to-Four Family Residential [Member] | Special Mention [Member] | Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	0	1,842
One-to-Four Family Residential [Member] | Substandard [Member] | Loans, Excluding Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	7,795	5,699
One-to-Four Family Residential [Member] | Substandard [Member] | Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	3,159	4,734
One-to-Four Family Residential [Member] | Doubtful [Member] | Loans, Excluding Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	0	0
One-to-Four Family Residential [Member] | Doubtful [Member] | Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	0	0
One-to-Four Family Residential [Member] | Unlikely to be Collected Financing Receivable [Member] | Loans, Excluding Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	0	0
One-to-Four Family Residential [Member] | Unlikely to be Collected Financing Receivable [Member] | Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	0	0
Commercial Land [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Allowance	799	489	460	488
Commercial Land [Member] | Loans, Excluding Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	189,779	142,834
Commercial Land [Member] | Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	15,344	18,565
Commercial Land [Member] | Pass [Member] | Loans, Excluding Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	183,701	137,850
Commercial Land [Member] | Pass [Member] | Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	9,104	10,778
Commercial Land [Member] | Special Mention [Member] | Loans, Excluding Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	4,217	0
Commercial Land [Member] | Special Mention [Member] | Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	0	198
Commercial Land [Member] | Substandard [Member] | Loans, Excluding Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	1,861	4,984
Commercial Land [Member] | Substandard [Member] | Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	6,240	7,589
Commercial Land [Member] | Doubtful [Member] | Loans, Excluding Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	0	0
Commercial Land [Member] | Doubtful [Member] | Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	0	0
Commercial Land [Member] | Unlikely to be Collected Financing Receivable [Member] | Loans, Excluding Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	0	0
Commercial Land [Member] | Unlikely to be Collected Financing Receivable [Member] | Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	0	0
Income Property Multifamily [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Allowance	9,159	9,234	11,033	9,551
Income Property Multifamily [Member] | Loans, Excluding Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	1,301,999	1,146,432
Income Property Multifamily [Member] | Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	60,513	70,592
Income Property Multifamily [Member] | Pass [Member] | Loans, Excluding Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	1,287,729	1,108,033
Income Property Multifamily [Member] | Pass [Member] | Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	51,435	55,985
Income Property Multifamily [Member] | Special Mention [Member] | Loans, Excluding Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	5,885	5,473
Income Property Multifamily [Member] | Special Mention [Member] | Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	1,892	3,950
Income Property Multifamily [Member] | Substandard [Member] | Loans, Excluding Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	8,385	32,926
Income Property Multifamily [Member] | Substandard [Member] | Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	7,186	10,657
Income Property Multifamily [Member] | Doubtful [Member] | Loans, Excluding Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	0	0
Income Property Multifamily [Member] | Doubtful [Member] | Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	0	0
Income Property Multifamily [Member] | Unlikely to be Collected Financing Receivable [Member] | Loans, Excluding Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	0	0
Income Property Multifamily [Member] | Unlikely to be Collected Financing Receivable [Member] | Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	0	0
Owner Occupied [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Allowance	5,007	3,605	6,362	9,606
Owner Occupied [Member] | Loans, Excluding Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	844,741	760,609
Owner Occupied [Member] | Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	64,541	81,722
Owner Occupied [Member] | Pass [Member] | Loans, Excluding Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	825,694	748,725
Owner Occupied [Member] | Pass [Member] | Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	58,629	67,653
Owner Occupied [Member] | Special Mention [Member] | Loans, Excluding Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	7,876	0
Owner Occupied [Member] | Special Mention [Member] | Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	346	111
Owner Occupied [Member] | Substandard [Member] | Loans, Excluding Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	11,171	11,884
Owner Occupied [Member] | Substandard [Member] | Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	5,566	13,958
Owner Occupied [Member] | Doubtful [Member] | Loans, Excluding Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	0	0
Owner Occupied [Member] | Doubtful [Member] | Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	0	0
Owner Occupied [Member] | Unlikely to be Collected Financing Receivable [Member] | Loans, Excluding Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	0	0
Owner Occupied [Member] | Unlikely to be Collected Financing Receivable [Member] | Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	0	0
Real Estate Construction Portfolio Segment [Member] | Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	6,941	21,650
Land And Acquisition [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Allowance	1,197	610	1,171	2,331
Land And Acquisition [Member] | Loans, Excluding Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	16,510	11,670
Land And Acquisition [Member] | Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	2,508	9,349
Land And Acquisition [Member] | Pass [Member] | Loans, Excluding Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	15,307	7,526
Land And Acquisition [Member] | Pass [Member] | Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	1,595	4,674
Land And Acquisition [Member] | Special Mention [Member] | Loans, Excluding Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	167	0
Land And Acquisition [Member] | Special Mention [Member] | Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	0	2,739
Land And Acquisition [Member] | Substandard [Member] | Loans, Excluding Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	1,036	4,144
Land And Acquisition [Member] | Substandard [Member] | Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	913	1,936
Land And Acquisition [Member] | Doubtful [Member] | Loans, Excluding Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	0	0
Land And Acquisition [Member] | Doubtful [Member] | Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	0	0
Land And Acquisition [Member] | Unlikely to be Collected Financing Receivable [Member] | Loans, Excluding Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	0	0
Land And Acquisition [Member] | Unlikely to be Collected Financing Receivable [Member] | Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	0	0
Residential Construction [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Allowance	1,860	822	635	864
Residential Construction [Member] | Loans, Excluding Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	98,521	41,992
Residential Construction [Member] | Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	1,845	5,432
Residential Construction [Member] | Pass [Member] | Loans, Excluding Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	96,031	36,270
Residential Construction [Member] | Pass [Member] | Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	741	3,008
Residential Construction [Member] | Special Mention [Member] | Loans, Excluding Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	909	2,352
Residential Construction [Member] | Special Mention [Member] | Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	0	0
Residential Construction [Member] | Substandard [Member] | Loans, Excluding Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	1,581	3,370
Residential Construction [Member] | Substandard [Member] | Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	1,104	2,424
Residential Construction [Member] | Doubtful [Member] | Loans, Excluding Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	0	0
Residential Construction [Member] | Doubtful [Member] | Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	0	0
Residential Construction [Member] | Unlikely to be Collected Financing Receivable [Member] | Loans, Excluding Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	0	0
Residential Construction [Member] | Unlikely to be Collected Financing Receivable [Member] | Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	0	0
Income Property Multifamily Construction [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Allowance	622	285	316	665
Income Property Multifamily Construction [Member] | Loans, Excluding Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	73,783	86,521
Income Property Multifamily Construction [Member] | Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	1,662	5,515
Income Property Multifamily Construction [Member] | Pass [Member] | Loans, Excluding Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	73,783	86,206
Income Property Multifamily Construction [Member] | Pass [Member] | Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	1,435	3,806
Income Property Multifamily Construction [Member] | Special Mention [Member] | Loans, Excluding Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	0	0
Income Property Multifamily Construction [Member] | Special Mention [Member] | Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	0	0
Income Property Multifamily Construction [Member] | Substandard [Member] | Loans, Excluding Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	0	315
Income Property Multifamily Construction [Member] | Substandard [Member] | Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	227	1,709
Income Property Multifamily Construction [Member] | Doubtful [Member] | Loans, Excluding Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	0	0
Income Property Multifamily Construction [Member] | Doubtful [Member] | Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	0	0
Income Property Multifamily Construction [Member] | Unlikely to be Collected Financing Receivable [Member] | Loans, Excluding Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	0	0
Income Property Multifamily Construction [Member] | Unlikely to be Collected Financing Receivable [Member] | Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	0	0
Owner Occupied Construction [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Allowance	434	58	102	35
Owner Occupied Construction [Member] | Loans, Excluding Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	58,944	38,916
Owner Occupied Construction [Member] | Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	926	1,354
Owner Occupied Construction [Member] | Pass [Member] | Loans, Excluding Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	58,055	38,916
Owner Occupied Construction [Member] | Pass [Member] | Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	926	1,074
Owner Occupied Construction [Member] | Special Mention [Member] | Loans, Excluding Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	0	0
Owner Occupied Construction [Member] | Special Mention [Member] | Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	0	0
Owner Occupied Construction [Member] | Substandard [Member] | Loans, Excluding Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	889	0
Owner Occupied Construction [Member] | Substandard [Member] | Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	0	280
Owner Occupied Construction [Member] | Doubtful [Member] | Loans, Excluding Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	0	0
Owner Occupied Construction [Member] | Doubtful [Member] | Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	0	0
Owner Occupied Construction [Member] | Unlikely to be Collected Financing Receivable [Member] | Loans, Excluding Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	0	0
Owner Occupied Construction [Member] | Unlikely to be Collected Financing Receivable [Member] | Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	0	0
Consumer Portfolio Segment [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Allowance	3,180	2,547	2,437	2,719
Consumer Portfolio Segment [Member] | Loans, Excluding Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	345,032	328,334
Consumer Portfolio Segment [Member] | Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	26,814	34,101
Consumer Portfolio Segment [Member] | Pass [Member] | Loans, Excluding Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	339,695	321,348
Consumer Portfolio Segment [Member] | Pass [Member] | Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	24,037	30,722
Consumer Portfolio Segment [Member] | Special Mention [Member] | Loans, Excluding Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	68	331
Consumer Portfolio Segment [Member] | Special Mention [Member] | Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	0	33
Consumer Portfolio Segment [Member] | Substandard [Member] | Loans, Excluding Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	5,269	6,188
Consumer Portfolio Segment [Member] | Substandard [Member] | Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	2,777	3,319
Consumer Portfolio Segment [Member] | Doubtful [Member] | Loans, Excluding Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	0	467
Consumer Portfolio Segment [Member] | Doubtful [Member] | Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	0	27
Consumer Portfolio Segment [Member] | Unlikely to be Collected Financing Receivable [Member] | Loans, Excluding Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	0	0
Consumer Portfolio Segment [Member] | Unlikely to be Collected Financing Receivable [Member] | Purchased Credit Impaired Loans [Member]
Financing Receivable, Recorded Investment [Line Items]
Loans and Leases Receivable, Gross, Carrying Amount	$0	$0

Other_Real_Estate_Owned_Summar

Other Real Estate Owned (Summary of Other Real Estate Owned) (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Other Real Estate Owned [Line Items]
Other Real Estate Owned, established through acquisition	$2,752	$14,708
Balance, beginning of period	35,927	26,987
Transfers in, net of write-downs ($0 and $90, respectively)	10,200	18,100
Other Real Estate Owned, additions and improvements	0	3,577
Writedowns Previously Recorded On Transfer In Of Real Estate Acquired Through Foreclosure	0	90
Additional OREO write-downs	-4,039	-2,035
Proceeds from Sale of Wholly Owned Real Estate and Real Estate Acquired in Settlement of Loans	28,559	35,949
Net realized gain on sale of other real estate owned	5,909	10,539	11,634
Balance, end of period	$22,190	$35,927	$26,987

FDIC_Losssharing_Asset_and_Cov2

FDIC Loss-sharing Asset and Covered Assets (Narrative) (Details) (USD $)	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Covered Assets And FDIC Loss Sharing Asset [Line Items]
Payment Of Clawback If Losses Less Than Stated Levels, Period After Acquisition									10 years 45 days
Amount of estimated clawback liability	$4,174,000				$3,900,000				$4,174,000	$3,900,000
Provision (recapture) for loan and lease losses	1,708,000	980,000	2,117,000	1,922,000	-3,682,000	3,313,000	288,000	-20,000	6,727,000	-101,000	39,367,000
Federal deposit insurance corporation loss-sharing indemnified assets	13,100,000				37,900,000				13,100,000	37,900,000
Federal deposit insurance corporation loss-sharing indemnified assets receivable	2,100,000				2,000,000				2,100,000	2,000,000
Writedowns Previously Recorded On Transfer In Of Real Estate Acquired Through Foreclosure									0	90,000
FDIC Indemnification Asset	15,174,000				39,846,000				15,174,000	39,846,000
FDIC Loss-sharing Asset, Write-downs of Other Real Estate									1,065,000	364,000
Non-Single Family Covered Assets	174,847,000								174,847,000
Single Family Covered Assets	46,799,000								46,799,000
Maximum [Member]
Covered Assets And FDIC Loss Sharing Asset [Line Items]
Loss Recovery Provision Effective Years									10 years
Loss Sharing Agreement Effective Years									10 years
Minimum [Member]
Covered Assets And FDIC Loss Sharing Asset [Line Items]
Loss Recovery Provision Effective Years									8 years
Loss Sharing Agreement Effective Years									5 years
Covered Loans [Member]
Covered Assets And FDIC Loss Sharing Asset [Line Items]
Percentage of loss shared by FDIC When Loss Share Thresholds Met					95.00%					95.00%
Percentage of loss shared by FDIC	80.00%								80.00%
FDIC Percentage Of Loss Recoveries	80.00%				95.00%				80.00%	95.00%
Fdic Loss Sharing Asset [Member]
Covered Assets And FDIC Loss Sharing Asset [Line Items]
FDIC Indemnification Asset	15,174,000				39,846,000				15,174,000	39,846,000	96,354,000
FDIC Loss-sharing Asset, Cash Payments Received									2,499,000	9,246,000
FDIC Loss-sharing Asset, Net Reimbursable Losses									-2,184,000	-2,245,000
FDIC Loss-sharing Asset, Amortization, Net									-21,279,000	-36,729,000
FDIC Loss-sharing Asset, Impairment (Recapture) of Loans									2,301,000	-2,609,000
FDIC Loss-sharing Asset, Disposals									2,179,000	6,177,000
FDIC Loss-sharing Asset, Other									103,000	134,000
Columbia River Bank [Member]
Covered Assets And FDIC Loss Sharing Asset [Line Items]
Amount of estimated clawback liability	4,017,000								4,017,000
FDIC Indemnification Asset	1,183,000								1,183,000
Non-Single Family Covered Assets	115,230,000								115,230,000
Single Family Covered Assets	11,166,000								11,166,000
American Marine Bank [Member]
Covered Assets And FDIC Loss Sharing Asset [Line Items]
Amount of estimated clawback liability	157,000								157,000
FDIC Indemnification Asset	4,927,000								4,927,000
Non-Single Family Covered Assets	17,984,000								17,984,000
Single Family Covered Assets	26,587,000								26,587,000
Summit Bank [Member]
Covered Assets And FDIC Loss Sharing Asset [Line Items]
Amount of estimated clawback liability	0								0
FDIC Indemnification Asset	4,712,000								4,712,000
Non-Single Family Covered Assets	14,352,000								14,352,000
Single Family Covered Assets	6,530,000								6,530,000
First Heritage Bank [Member]
Covered Assets And FDIC Loss Sharing Asset [Line Items]
Amount of estimated clawback liability	0								0
FDIC Indemnification Asset	4,352,000								4,352,000
Non-Single Family Covered Assets	27,281,000								27,281,000
Single Family Covered Assets	$2,516,000								$2,516,000

Premises_and_Equipment_Details

Premises and Equipment (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	$221,525,000	$205,625,000
Less accumulated depreciation and amortization	-49,435,000	-50,893,000
Total	172,090,000	154,732,000
Depreciation and amortization expense	10,900,000	10,200,000	6,300,000
Land [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	52,338,000	48,992,000
Building [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	103,240,000	94,878,000
Leasehold Improvements [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	21,199,000	14,254,000
Furniture and Fixtures [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	28,486,000	29,465,000
Vehicles [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	596,000	546,000
Computer Software, Intangible Asset [Member]
Property, Plant and Equipment [Line Items]
Property, Plant and Equipment, Gross	$15,666,000	$17,490,000

Goodwill_and_Intangible_Assets2

Goodwill and Intangible Assets (Schedule of Goodwill and Intangible Assets) (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Goodwill and Intangible Assets [Line Items]
Indefinite-Lived Intangible Assets (Excluding Goodwill)	$919	$919	$0
Intangible Assets, Net (Excluding Goodwill)	30,459	25,852	15,721
Goodwill and Intangible Assets [Roll Forward]
Total goodwill, beginning of period	343,952	115,554	115,554
Established through acquisitions	38,585	228,398	0
Total goodwill, end of period	382,537	343,952	115,554
Core deposit intangible, net, beginning of period	25,852
CDI current period amortization	-6,293	-6,045	-4,445
Total core deposit intangible, end of period	30,459	25,852
Total goodwill and intangible assets, end of period	412,996	369,804	131,275
Core Deposits [Member]
Goodwill and Intangible Assets [Roll Forward]
Gross core deposit intangible balance, beginning of period	47,698	32,441	32,441
Accumulated amortization, beginning of period	-22,765	-16,720	-12,275
Core deposit intangible, net, beginning of period	24,933	15,721	20,166
Established through acquisitions	10,900	15,257	0
CDI current period amortization	-6,293	-6,045	-4,445
Total core deposit intangible, end of period	$29,540	$24,933	$15,721
Estimated life of CDI, in years	10 years

Goodwill_and_Intangible_Assets3

Goodwill and Intangible Assets (Summary of Estimated Future Amortization Expense of Core Deposit Intangibles) (Details) (Core Deposits [Member], USD $)	Dec. 31, 2014
In Thousands, unless otherwise specified
Core Deposits [Member]
Future Amortization Expense For Core Deposit Intangibles
2015	$6,882
2016	5,945
2017	4,913
2018	3,855
2019	$2,951

Deposits_Details

Deposits (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
Deposits [Abstract]
Brokered money market accounts	$83,402,000	$41,765,000
Demand and other noninterest-bearing	2,651,373,000	2,171,703,000
Interest-bearing demand	1,304,258,000	1,170,006,000
Money market	1,760,331,000	1,569,261,000
Savings	615,721,000	496,444,000
Certificates of deposit less than $100,000	288,261,000	288,943,000
Total core deposits	6,619,944,000	5,696,357,000
Certificates of deposit greater than $100,000	202,014,000	201,498,000
Certificates of deposit insured by CDARS®	18,429,000	19,488,000
Subtotal	6,923,789,000	5,959,108,000
Deposits, Valuation Adjustment From Acquisition Accounting	933,000	367,000
Total deposits	6,924,722,000	5,959,475,000
Deposit Liabilities Reclassified as Loans Receivable	1,300,000	1,100,000
Time Deposits, Fiscal Year Maturity [Abstract]
2015	162,828,000
2016	40,375,000
2017	8,069,000
2018	3,822,000
2019	3,982,000
Thereafter	108,000
Total	$219,184,000

Federal_Home_Loan_Bank_and_Fed2

Federal Home Loan Bank and Federal Reserve Bank Borrowings (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
FHLB Fixed Rate Advances, Maturities Summary [Abstract]
FHLB Fixed Rate Advances, Weighted Average Interest Rate, Within 1 year	0.27%
FHLB Fixed Rate Advances, Amount, Within 1 year	$210,000
Federal Home Loan Bank, Advances, Maturities Summary, Average Interest Rate, One To Five Years From Balance Sheet Date	5.66%
FHLB Fixed Rate Advances, Over 1 through 5 years	1,000
FHLB Fixed Rate Advances, Weighted Average Interest Rate, Due after 10 years	5.37%
FHLB Fixed Rate Advances, Due after 10 years	5,000
FHLB Fixed Rate Advances, Total Amount before valuation adjustment	216,000
Valuation adjustment from acquisition accounting	568
FHLB Fixed Rate Advances, Total Amount	216,568
Federal Home Loan Bank, Advances, Activity for Year [Abstract]
FHLB Advances	216,568	36,606	6,644
Average balance during the year	44,876	51,030	100,337
Maximum month-end balance during the year	216,568	190,631	118,967
Weighted average rate during the year	0.74%	1.12%	2.79%
Weighted average rate at December 31	0.41%	1.09%	5.42%
FHLB Advances, Collateral Pledged	1,083,879	1,075,389
FHLB Borrowing Capacity	865,138	1,037,159
Federal Reserve Bank, Advances, Collateral Pledged	86,130	85,452
Federal Reserve Bank borrowing capacity	86,130	85,452
Securities Investment [Member]
Federal Home Loan Bank, Advances, Activity for Year [Abstract]
Federal Reserve Bank, Advances, Collateral Pledged	40,128	40,210
Loans Receivable [Member]
Federal Home Loan Bank, Advances, Activity for Year [Abstract]
FHLB Advances, Collateral Pledged	1,083,879	1,075,389
Commercial Loan [Member]
Federal Home Loan Bank, Advances, Activity for Year [Abstract]
Federal Reserve Bank, Advances, Collateral Pledged	$46,002	$45,242

Securities_Sold_Under_Agreemen1

Securities Sold Under Agreements to Repurchase (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
Assets Sold under Agreements to Repurchase [Line Items]
Carrying amount of securities pledged as collateral	$526,643,000	$362,787,000
Available-for-sale Securities [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Assets Sold under Agreements to Repurchase, Sweep, Interest rate	0.12%
Assets Sold under Agreements to Repurchase, Sweep, Carrying Amount	80,100,000
Assets Sold under Agreements to Repurchase, Term, Carrying Amounts	25,000,000
Assets Sold under Agreements to Repurchase, Term, Interest Rate	1.88%
Repurchase Agreements, Sweep [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Carrying amount of securities pledged as collateral	103,000,000
Repurchase Agreements,Term [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Carrying amount of securities pledged as collateral	$28,400,000

Other_Borrowings_Details

Other Borrowings (Details) (USD $)	12 Months Ended
In Millions, unless otherwise specified	Dec. 31, 2014	Nov. 01, 2014
Subordinated Borrowing [Line Items]
Repayments of subordinated debt, Intermountain Statutory Trust I	$8.30
Subordinated Borrowing, Interest Rate	3.03%
Intermountain Community Bancorp [Member]
Subordinated Borrowing [Line Items]
Business Combination, Purchase Price Allocation, Junior Subordinated Debentures		$16.50

Derivatives_and_Balance_Sheet_2

Derivatives and Balance Sheet Offsetting (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Derivative [Line Items]
Gain (Loss) on Derivative Instruments, Net, Pretax	$51,000	$0
Not Designated as Hedging Instrument [Member] | Interest Rate Contracts [Member]
Derivative [Line Items]
Derivative, Notional Amount	215,600,000	179,500,000
Not Designated as Hedging Instrument [Member] | Other Assets [Member] | Interest Rate Contracts [Member]
Derivative [Line Items]
Derivative Asset, Fair Value, Gross Asset	11,800,000	9,044,000
Not Designated as Hedging Instrument [Member] | Other Liabilities [Member] | Interest Rate Contracts [Member]
Derivative [Line Items]
Derivative Liability, Fair Value, Gross Liability	$11,851,000	$9,044,000

Derivatives_and_Balance_Sheet_3

Derivatives and Balance Sheet Offsetting Balance Sheet Offsetting (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Balance Sheet Offsetting [Line Items]
Repurchase agreements, amounts offset in balance sheet	$0	$0
repurchase agreements, net amount presented in statement of financial position	105,080	25,000
Securities Sold under Agreements to Repurchase, Collateral, Right to Reclaim Securities	-105,080	-25,000
securities sold under agreements to repurchase, amount not offset	0	0
Interest Rate Contracts [Member]
Balance Sheet Offsetting [Line Items]
Derivative Assets, Gross Amounts Offset in the Balance Sheets	0	0
Derivative Asset	11,800	9,044
Derivative, Collateral, Obligation to Return Securities	0	0
Derivative Asset, Fair Value, Amount Not Offset Against Collateral	11,800	9,044
Derivative Liability, Gross Amounts Offset in Balance Sheets	0	0
Derivative Liability	11,851	9,044
Derivative, Collateral, Right to Reclaim Securities	-11,851	-9,044
Derivative Liability, Fair Value, Amount Not Offset Against Collateral	0	0
Not Designated as Hedging Instrument [Member] | Other Assets [Member] | Interest Rate Contracts [Member]
Balance Sheet Offsetting [Line Items]
Derivative Asset, Fair Value, Gross Asset	11,800	9,044
Not Designated as Hedging Instrument [Member] | Other Liabilities [Member] | Interest Rate Contracts [Member]
Balance Sheet Offsetting [Line Items]
Derivative Liability, Fair Value, Gross Liability	11,851	9,044
Available-for-sale Securities [Member]
Balance Sheet Offsetting [Line Items]
Assets Sold under Agreements to Repurchase, Carrying Amount	$105,080	$25,000

Employee_Benefit_Plans_Details

Employee Benefit Plans (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
	period
Employee Benefit [Line Items]
Defined Benefit Plan, Business Combinations and Acquisitions, Benefit Obligation	$511,000	$3,398,000
Number of Look-back Period Under Employee Stock Purchase Plan	2
Look-back Period Under Employee Stock Purchase Plan	6 months
Discount On Common Stock Under Employee Stock Purchase Plan, Percent	10.00%
Stock Issued During Period, Shares, Employee Stock Purchase Plans	34,168	32,598	39,393
Stock Issued During Period, Value, Employee Stock Purchase Plan	904,000	686,000	725,000
Shares Available For Purchase Under Employee Stock Purchase Plan	541,744
Defined Benefit Plan, Change in Benefit Obligation [Roll Forward]
Balance at beginning of year	16,423,000	11,616,000
Change in actuarial loss	0	2,212,000
Benefit expense	1,325,000	1,880,000
Benefit payments	-1,718,000	-2,683,000
Balance at end of year	16,541,000	16,423,000	11,616,000
Pension Plan [Member]
Employee Benefit [Line Items]
Deferred Compensation Arrangement with Individual, Service Period	6 months
Deferred Compensation Arrangement with Individual, Contribution To Plan By Employee, Percent Of Eligible Compensation	75.00%
Deferred Compensation Arrangement with Individual, Contribution Requirements, Matching Percent	50.00%
Deferred Compensation Arrangement with Individual, Employer Contribution	2,000,000	1,900,000	1,400,000
Pension Plan [Member] | Minimum [Member]
Employee Benefit [Line Items]
Deferred Compensation Arrangement with Individual, Eligible Age	18
Pension Plan [Member] | Maximum [Member]
Employee Benefit [Line Items]
Deferred Compensation Arrangement with Individual, Contribution Requirements, Percent Of Each Employee Compensation	3.00%
Deferred Profit Sharing [Member]
Employee Benefit [Line Items]
Deferred Compensation Arrangement with Individual, Service Period	6 months
Deferred Compensation Arrangement with Individual, Contribution To Plan By Employee, Percent Of Eligible Compensation	75.00%
Deferred Compensation Arrangement with Individual, Contribution Requirements, Matching Percent	50.00%
Deferred Compensation Arrangement with Individual, Employer Contribution	4,400,000	4,000,000	2,900,000
Deferred Profit Sharing [Member] | Minimum [Member]
Employee Benefit [Line Items]
Deferred Compensation Arrangement with Individual, Eligible Age	18
Deferred Profit Sharing [Member] | Maximum [Member]
Employee Benefit [Line Items]
Deferred Compensation Arrangement with Individual, Contribution Requirements, Percent Of Each Employee Compensation	3.00%
ESP Plan [Member]
Employee Benefit [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Discount from Market Price, Purchase Date	90.00%
Unit Plans [Member]
Employee Benefit [Line Items]
Deferred Compensation Arrangement with Individual, Recorded Liability	4,800,000	4,700,000
Deferred Compensation Arrangement with Individual, Compensation Expense	588,000	458,000	677,000
Unit Plans [Member] | Minimum [Member]
Employee Benefit [Line Items]
Deferred Compensation Arrangement with Individual, Vesting Period	4 years
Deferred Compensation Arrangement with Individual, Benefit Period	5 years
Unit Plans [Member] | Maximum [Member]
Employee Benefit [Line Items]
Deferred Compensation Arrangement with Individual, Vesting Period	10 years
Deferred Compensation Arrangement with Individual, Benefit Period	10 years
SERP [Member]
Employee Benefit [Line Items]
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate	5.10%
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Normal Retirement Age	65
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Annual Cost Of Living Benefit Adjustment	2.00%
Defined Benefit Plan, Expected Future Benefit Payments, Fiscal Year Maturity [Abstract]
2015	975,000
2016	994,000
2017	1,088,000
2018	1,349,000
2019	1,384,000
2020 through 2024	9,580,000
Total	$15,370,000

Commitments_and_Contingent_Lia2

Commitments and Contingent Liabilities (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Minimum future rental payments:
2015	$8,557,000
2016	6,602,000
2017	5,353,000
2018	4,671,000
2019	4,308,000
Thereafter	18,121,000
Total minimum payments	47,612,000
Operating Leases, Rent Expense, Sublease Rentals	756,000	673,000	639,000
Operating Leases, Rent Expense, Net	8,300,000	8,500,000	4,500,000
Commitments to Extend Credit [Member]
Minimum future rental payments:
Fair Value Disclosure, Off-balance Sheet Risks, Amount, Liability	1,580,000,000	1,370,000,000
Standby Letters of Credit [Member]
Minimum future rental payments:
Fair Value Disclosure, Off-balance Sheet Risks, Amount, Liability	36,700,000
Commercial Letter of Credit and other off-balance sheet liabilities [Member]
Minimum future rental payments:
Fair Value Disclosure, Off-balance Sheet Risks, Amount, Liability	$4,400,000	$0

Shareholders_Equity_Details

Shareholders' Equity (Details) (USD $)	0 Months Ended				12 Months Ended	0 Months Ended		12 Months Ended
	Oct. 23, 2014	Jul. 23, 2014	Apr. 23, 2014	Jan. 23, 2014	Dec. 31, 2014	Jan. 29, 2015	Apr. 02, 2013	Dec. 31, 2013
Class of Stock [Line Items]
Preferred Stock Converted Into Common Stock, Shares					102,363
Class of Warrant or Right, Exercise Price of Warrants or Rights							8.58
Class of Warrant or Right, Number of Securities Called by Warrants or Rights					0
Warrant Activity, Net Shares					1,722,497
Declared quarterly cash dividend	$0.16	$0.14	$0.12	$0.12
Special Dividends Payable, Amount Per Share	$0.14	$0.14	$0.12
Stock Repurchase Program, Number of Shares Authorized to be Repurchased					2,000,000
Stock Repurchased During Period, Shares					0
Dividend Declared [Member]
Class of Stock [Line Items]
Declared quarterly cash dividend						$0.16
Special Dividends Payable, Amount Per Share						$0.14
Preferred Stock [Member]
Class of Stock [Line Items]
Stock Issued During Period, Shares, New Issues					0		8,782	9,000

Accumulated_Other_Comprehensiv2

Accumulated Other Comprehensive Income (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated Other Comprehensive Income (Loss), Net of Tax	$5,621		($12,044)		$20,149
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	17,922		-32,159
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	-257	[1]	-34	[1]
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	17,665		-32,193		-4,984
Accumulated Net Unrealized Investment Gain (Loss) [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated Other Comprehensive Income (Loss), Net of Tax	7,462		-10,108		20,918
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	17,922		-30,727
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	-352	[1]	-299	[1]
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	17,570		-31,026
Accumulated Defined Benefit Plans Adjustment [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated Other Comprehensive Income (Loss), Net of Tax	-1,841		-1,936		-769
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	0		-1,432
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	95	[1]	265	[1]
Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent	$95		($1,167)
[1]	(2) See following table for details about these reclassifications.

Accumulated_Other_Comprehensiv3

Accumulated Other Comprehensive Income Amounts reclassified from Accumulated Other Comprehensive Income (Details) (USD $)	3 Months Ended								12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Gain on sale of investment securities, net									$552	$462	$3,733
Income before income taxes	28,087	31,188	29,870	28,640	27,884	20,010	22,005	17,111	117,785	87,010	63,705
Income Tax Expense (Benefit)	-9,167	-9,605	-8,643	-8,796	-7,911	-6,734	-7,414	-4,935	-36,211	-26,994	-17,562
Net income (loss)	18,920	21,583	21,227	19,844	19,973	13,276	14,591	12,176	81,574	60,016	46,143
Compensation and employee benefits									130,864	125,432	85,434
Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Net Unrealized Investment Gain (Loss) [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Gain on sale of investment securities, net									552	462
Income before income taxes									552	462
Income Tax Expense (Benefit)									-200	-163
Net income (loss)									352	299
Reclassification out of Accumulated Other Comprehensive Income [Member] | Accumulated Defined Benefit Plans Adjustment [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Income before income taxes									-149	-400
Income Tax Expense (Benefit)									54	135
Net income (loss)									-95	-265
Compensation and employee benefits									($149)	($400)

Fair_Value_Accounting_and_Meas2

Fair Value Accounting and Measurement (Financial Assets And Liabilities Accounted for Fair Value On Recurring Basis) (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	$2,098,257	$1,664,111
Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	2,098,257	1,664,111
Other assets (Interest rate contracts)	11,800	9,044
Other liabilities (Interest rate contracts)	11,851	9,044
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	20,499	20,114
Other assets (Interest rate contracts)	0	0
Other liabilities (Interest rate contracts)	0	0
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	2,077,758	1,643,997
Other assets (Interest rate contracts)	11,800	9,044
Other liabilities (Interest rate contracts)	11,851	9,044
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	0	0
Other assets (Interest rate contracts)	0	0
Other liabilities (Interest rate contracts)	0	0
U.S. Government Agency and Sponsored Enterprise Mortgage-Back Securities and Collateralized Mortgage Obligations [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	1,162,387	948,408
U.S. Government Agency and Sponsored Enterprise Mortgage-Back Securities and Collateralized Mortgage Obligations [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	0	0
U.S. Government Agency and Sponsored Enterprise Mortgage-Back Securities and Collateralized Mortgage Obligations [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	1,162,387	948,408
U.S. Government Agency and Sponsored Enterprise Mortgage-Back Securities and Collateralized Mortgage Obligations [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	0	0
State and Municipal Securities [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	496,484	364,470
State and Municipal Securities [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	0	0
State and Municipal Securities [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	496,484	364,470
State and Municipal Securities [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	0	0
U.S. Government Agency [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	413,706	326,039
U.S. Government Agency [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	0	0
U.S. Government Agency [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	413,706	326,039
U.S. Government Agency [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	0	0
US Treasury Securities [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	20,499	20,114
US Treasury Securities [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	20,499	20,114
US Treasury Securities [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	0	0
US Treasury Securities [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	0	0
Other Securities [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	5,181	5,080
Other Securities [Member] | Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	0	0
Other Securities [Member] | Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	5,181	5,080
Other Securities [Member] | Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Securities available for sale	$0	$0

Fair_Value_Accounting_and_Meas3

Fair Value Accounting and Measurement (Financial Assets Accounted For Fair Value On Nonrecurring Basis) (Details) (Fair Value, Measurements, Nonrecurring [Member], USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans		$8,973
Assets, Fair Value Disclosure	5,365	14,666
Losses During Period	1,008	2,766
Other Real Estate Owned Fair Value	5,365	5,693
Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans		0
Assets, Fair Value Disclosure	0	0
Other Real Estate Owned Fair Value	0	0
Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans		0
Assets, Fair Value Disclosure	0	0
Other Real Estate Owned Fair Value	0	0
Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans		8,973
Other Real Estate Owned, Fair Value Disclosure	5,365	5,693
Assets, Fair Value Disclosure	5,365	14,666
Other Real Estate Owned Fair Value	5,365	5,693
Impaired Loans [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Losses During Period		1,536
Other Real Estate Owned [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Losses During Period	$1,008	$1,230

Fair_Value_Accounting_and_Meas4

Fair Value Accounting and Measurement (Quantitative Information About Level 3 Fair Value Measurements) (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014						Dec. 31, 2013
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value Inputs, Assets, Quantitative Information [Table Text Block]	The range and weighted-average of the significant unobservable inputs used to fair value our Level 3 nonrecurring assets during 2014 and 2013, along with the valuation techniques used, are shown in the following tables:
		Fair value  at		Valuation Technique	Unobservable Input	Range (Weighted Average) (1)
		December 31, 2014
		(dollars in thousands)
	OREO	$	5,365	Fair Market Value of Collateral	Adjustment to Appraisal Value	N/A (2)
	(1) Discount applied to appraisal value, letter of intent to purchase, or stated value (in the case of accounts receivable and inventory).
	(2) Quantitative disclosures are not provided for OREO because there were no adjustments made to the appraisal value during the current period.
		Fair value  at		Valuation Technique	Unobservable Input	Range (Weighted Average) (1)
		December 31, 2013
		(dollars in thousands)
	Impaired loans	$	8,973	Fair Market Value of Collateral	Adjustment to Appraisal Value	N/A (2)
	OREO (3)	5,693		Fair Market Value of Collateral	Adjustment to Appraisal Value	N/A (2)
	(1) Discount applied to appraisal value, letter of intent to purchase, or stated value (in the case of accounts receivable and inventory).
	(2) Quantitative disclosures are not provided for impaired loans and OREO because there were no adjustments made to the appraisal value during the current period.
	(3) Reclassified to conform to the current period’s presentation. The reclassification was limited to combining historically reported noncovered OREO and covered OREO into one line item for OREO.
Fair Value, Measurements, Nonrecurring [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Impaired loans							$8,973
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Nonrecurring [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Impaired loans							8,973
Other Real Estate Owned, Fair Value Disclosure	5,365						$5,693

Fair_Value_Accounting_and_Meas5

Fair Value Accounting and Measurement Fair Value Accounting and Measurement (Carrying Amounts and Estimated Fair Values of Selected Financial Instruments) (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Assets
Interest-earning deposits with banks	$16,949	$14,531
Securities available for sale	2,098,257	1,664,111
Reported Value Measurement [Member]
Assets
Cash and due from banks	171,221	165,030
Interest-earning deposits with banks	16,949	14,531
Securities available for sale	2,098,257	1,664,111
FHLB stock	33,365	32,529
Loans held for sale	1,116	735
Loans	5,375,809	4,444,842
FDIC loss-sharing asset	15,174	39,846
Interest rate contracts	11,800	9,044
Liabilities
Deposits	6,924,722	5,959,475
FHLB Advances	216,568	36,606
Repurchase agreements	105,080	25,000
Other borrowings	8,248
Interest rate contracts	11,851	9,044
Estimate of Fair Value Measurement [Member]
Assets
Cash and due from banks	171,221	165,030
Interest-earning deposits with banks	16,949	14,531
Securities available for sale	2,098,257	1,664,111
FHLB stock	33,365	32,529
Loans held for sale	1,116	735
Loans	5,516,286	4,605,038
FDIC loss-sharing asset	4,054	11,248
Interest rate contracts	11,800	9,044
Liabilities
Deposits	6,921,804	5,958,747
FHLB Advances	217,296	35,080
Repurchase agreements	106,171	26,361
Other borrowings	8,248
Interest rate contracts	11,851	9,044
Fair Value, Inputs, Level 1 [Member] | Estimate of Fair Value Measurement [Member]
Assets
Cash and due from banks	171,221	165,030
Interest-earning deposits with banks	16,949	14,531
Securities available for sale	20,499	20,114
FHLB stock	0	0
Loans held for sale	0	0
Loans	0	0
FDIC loss-sharing asset	0	0
Interest rate contracts	0	0
Liabilities
Deposits	6,416,017	5,449,546
FHLB Advances	0	0
Repurchase agreements	0	0
Other borrowings	0
Interest rate contracts	0	0
Fair Value, Inputs, Level 2 [Member] | Estimate of Fair Value Measurement [Member]
Assets
Cash and due from banks	0	0
Interest-earning deposits with banks	0	0
Securities available for sale	2,077,758	1,643,997
FHLB stock	33,365	32,529
Loans held for sale	1,116	735
Loans	0	0
FDIC loss-sharing asset	0	0
Interest rate contracts	11,800	9,044
Liabilities
Deposits	505,787	509,201
FHLB Advances	217,296	35,080
Repurchase agreements	106,171	26,361
Other borrowings	8,248
Interest rate contracts	11,851	9,044
Fair Value, Inputs, Level 3 [Member] | Estimate of Fair Value Measurement [Member]
Assets
Cash and due from banks	0	0
Interest-earning deposits with banks	0	0
Securities available for sale	0	0
FHLB stock	0	0
Loans held for sale	0	0
Loans	5,516,286	4,605,038
FDIC loss-sharing asset	4,054	11,248
Interest rate contracts	0	0
Liabilities
Deposits	0	0
FHLB Advances	0	0
Repurchase agreements	0	0
Other borrowings	0
Interest rate contracts	$0	$0

Fair_Value_Accounting_and_Meas6

Fair Value Accounting and Measurement Fair Value, quantitative inputs to Level 3 measurements (Details) (Fair Value, Measurements, Nonrecurring [Member], USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Impaired loans		$8,973
Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Impaired loans		8,973
Other Real Estate Owned, Fair Value Disclosure	$5,365	$5,693

Earnings_Per_Common_Share_Sche

Earnings Per Common Share (Schedule of Basic and Diluted Earnings Per Share) (Details) (USD $)	3 Months Ended								12 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Earnings Per Share, Basic, by Common Class, Including Two Class Method [Line Items]
Basic earnings allocated to common shareholders									$80,637	$59,398	$45,700
Net income (loss)	18,920	21,583	21,227	19,844	19,973	13,276	14,591	12,176	81,574	60,016	46,143
Earnings allocated to participating securities - preferred shares									157	95	0
Earnings allocated to participating securities - nonvested restricted shares									780	523	443
Weighted average common shares outstanding									52,618	47,993	39,260
Earnings (loss) basic (dollars per share)	$0.34	$0.41	$0.40	$0.38	$0.39	$0.26	$0.28	$0.31	$1.53	$1.24	$1.16
Earnings allocated to common shareholders, Diluted									$80,640	$59,407	$45,700
Weighted average number of common shares outstanding									52,618	47,993	39,260
Dilutive effect of equity awards and warrants									565	1,058	3
Weighted average diluted common shares outstanding									53,183	49,051	39,263
Earnings (loss) diluted (dollars per share)	$0.34	$0.41	$0.40	$0.37	$0.38	$0.25	$0.28	$0.31	$1.52	$1.21	$1.16
Potentially dilutive share options that were not included in the computation of diluted EPS because to do so would be anti-dilutive.									64	64	9

ShareBased_Payments_Share_Awar

Share-Based Payments (Share Awards) (Details) (USD $)	12 Months Ended
In Millions, except Share data, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Allocated Share-based Compensation Expense	$2.90	$2.80	$1.60
Share-based compensation, number authorized (in shares)	1,800,000
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number	519,785	410,598	384,090	362,675
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value	$23.03	$20.79	$19.54	$19.24
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period	246,068	203,441	180,841
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period, Weighted Average Grant Date Fair Value	$25.97	$20.78	$21.32
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period	-108,371	-117,153	-118,511
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Weighted Average Grant Date Fair Value	$21.45	$16.90	$21.65
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeited in Period	-28,510	-59,780	-40,915
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeited in Period, Weighted Average Grant Date Fair Value	$21.92	$20.24	$18.60
Employee Service Share-based Compensation, Nonvested Awards, Total Compensation Cost Not yet Recognized	7
Employee Service Share-based Compensation, Nonvested Awards, Total Compensation Cost Not yet Recognized, Period for Recognition	2 years 4 months 25 days
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Total Fair Value	$2.30	$2.50	$2.50

ShareBased_Payments_Share_Opti

Share-Based Payments (Share Options) (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Allocated Share-based Compensation Expense	$2,900,000	$2,800,000	$1,600,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Balance at beginning of year (in shares)	116,197
Granted (in shares)	0	222,110	0
Forfeited (in shares)	-8,753
Expired (in shares)	-22,330
Exercised (in shares)	-9,116
Balance at end of year (in shares)	75,998	116,197
Total Exercisable Shares	75,998
Weighted Average Exercise Price at beginning of year	$65.01
Weighted Average Exercise Price, Forfeited	$75.32
Weighted Average Exercise Price, Expired	$91.95
Weighted Average Exercise Price, Exercised	$12.09
Weighted Average Exercise Price at end of year	$62.41	$65.01
Exercisable, Weighted Average Exercise Price	$62.41
Weighted Average Remaining Contractual Term	2 years 4 months 25 days
Aggregate Intrinsic Value	391,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Number	75,998
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Weighted Average Exercise Price	$62.41
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Weighted Average Remaining Contractual Term	2 years 4 months 25 days
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Aggregate Intrinsic Value	391,000
Exercisable, Weighted Average Remaining Contractual Term	2 years 4 months 25 days
Exercisable, Aggregate Intrinsic Value	391,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period, Total Intrinsic Value	138,000	410,000	5,000
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Abstract]
Number of Option Shares	75,998
Weighted Average Remaining Contractual Life	2 years 5 months 0 days
Weighted Average Exercise Price of Option Shares	$62.41
Number of Exercisable Option Shares	75,998
Weighted Average Exercise Price of Exercisable Option Shares	$62.41
Stock-based compensation expense	$2,859,000	$2,844,000	$1,622,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Weighted Average Grant Date Fair Value		$3.06
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested, Number of Shares	0
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range From 0.00 To 9.99 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Abstract]
Range of Exercise Prices, Lower Limit	$0
Range of Exercise Prices, Upper Limit	$9.99
Number of Option Shares	21,579
Weighted Average Remaining Contractual Life	4 years 3 months 24 days
Weighted Average Exercise Price of Option Shares	$9.91
Number of Exercisable Option Shares	21,579
Weighted Average Exercise Price of Exercisable Option Shares	$9.91
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range From 10.00 To 19.99 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Abstract]
Range of Exercise Prices, Lower Limit	$10
Range of Exercise Prices, Upper Limit	$19.99
Number of Option Shares	600
Weighted Average Remaining Contractual Life	2 years 7 months 19 days
Weighted Average Exercise Price of Option Shares	$12.61
Number of Exercisable Option Shares	600
Weighted Average Exercise Price of Exercisable Option Shares	$12.61
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range From 20.00 To 29.99 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Abstract]
Range of Exercise Prices, Lower Limit	$20
Range of Exercise Prices, Upper Limit	$29.99
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range From 30.00 To 39.99 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Abstract]
Range of Exercise Prices, Lower Limit	$30
Range of Exercise Prices, Upper Limit	$39.99
Number of Option Shares	4,051
Weighted Average Remaining Contractual Life	2 years 1 month 21 days
Weighted Average Exercise Price of Option Shares	$30.86
Number of Exercisable Option Shares	4,051
Weighted Average Exercise Price of Exercisable Option Shares	$30.86
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range From 40.00 To 49.99 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Abstract]
Range of Exercise Prices, Lower Limit	$40
Range of Exercise Prices, Upper Limit	$49.99
Number of Option Shares	349
Weighted Average Remaining Contractual Life	3 years 5 months 26 days
Weighted Average Exercise Price of Option Shares	$44.49
Number of Exercisable Option Shares	349
Weighted Average Exercise Price of Exercisable Option Shares	$44.49
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range From 50.00 To 146.41 [Member]
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range [Abstract]
Range of Exercise Prices, Lower Limit	$50
Range of Exercise Prices, Upper Limit	$146.41
Number of Option Shares	49,419
Weighted Average Remaining Contractual Life	1 year 7 months 6 days
Weighted Average Exercise Price of Option Shares	$88.65
Number of Exercisable Option Shares	49,419
Weighted Average Exercise Price of Exercisable Option Shares	$88.65
Stock Option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share Based Compensation Arrangement By Share Based Payment Award, Exercisable Period	5 years
Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period	3 years
Share Based Compensation Arrangement By Share Based Payment Award, Maximum Term	10 years

Income_Tax_Details

Income Tax (Details) (USD $)	3 Months Ended									12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013		Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013		Dec. 31, 2012
Income Tax Contingency [Line Items]
Unrecognized tax position	$0									$0
Interest and penalties on unrecognized tax benefits										0
Federal operating loss carryforwards, set to begin to expire in 2024	30,700,000									30,700,000
Idaho state operating loss carryforwards, set to begin to expire in 2024	38,100,000									38,100,000
Deferred Tax Assets, Operating Loss Carryforwards	14,929,000				1,250,000	[1]				14,929,000	1,250,000	[1]
State operating loss carryforwards, set to begin to expire in 2024	13,500,000									13,500,000
Federal tax credit carryforwards	561,000									561,000
State tax credit carryforwards, set to expire in 2015	1,600,000									1,600,000
Current tax (benefit) expense										21,565,000	21,581,000		21,218,000
Deferred tax expense (benefit)										14,646,000	5,413,000		-3,656,000
Income tax expense (benefit)	9,167,000	9,605,000	8,643,000	8,796,000	7,911,000		6,734,000	7,414,000	4,935,000	36,211,000	26,994,000		17,562,000
Deferred tax assets:
Allowance for loan and lease losses	26,341,000				27,196,000					26,341,000	27,196,000
Supplemental executive retirement plan	9,037,000				8,565,000					9,037,000	8,565,000
Stock option and restricted stock	1,177,000				917,000					1,177,000	917,000
OREO	1,101,000				7,929,000					1,101,000	7,929,000
Nonaccrual interest	68,000				2,354,000					68,000	2,354,000
Deferred tax assets, purchase accounting	15,272,000				15,551,000					15,272,000	15,551,000
Deferred Tax Assets, Unrealized Losses on Available-for-Sale Securities, Gross	0				7,176,000					0	7,176,000
deferred tax liabilities, unrealized gains on available-for-sale securities	2,987,000				0					2,987,000	0
Other	532,000				491,000	[1]				532,000	491,000	[1]
Total deferred tax assets	68,457,000				71,429,000					68,457,000	71,429,000
Deferred tax liabilities:
Asset purchase tax basis difference	-6,595,000				-7,754,000					-6,595,000	-7,754,000
FHLB stock dividends	-4,086,000				-4,159,000					-4,086,000	-4,159,000
Deferred loan fees	-4,691,000				-4,512,000					-4,691,000	-4,512,000
Depreciation	-5,394,000				-7,076,000					-5,394,000	-7,076,000
Total deferred tax liabilities	23,753,000				23,501,000					23,753,000	23,501,000
Net deferred tax (liability) asset	44,704,000				47,928,000					44,704,000	47,928,000
Reconciliation of effective income tax rate with federal statutory tax rate
Income tax based on statutory rate										41,225,000	30,454,000		22,297,000
Income tax based on statutory rate, percent										35.00%	35.00%		35.00%
Tax exempt instrument										-5,328,000	-4,113,000		-3,906,000
Tax exempt instrument, percent										-5.00%	-5.00%		-6.00%
Life insurance proceeds										-1,352,000	-1,250,000		-1,001,000
Life insurance proceeds, percent										-1.00%	-1.00%		-2.00%
effective income tax rate reconciliation, nondeductible expense, business combination, amount										448,000	1,362,000		0
effective income tax rate reconciliation, nondeductible expense, business combination, percent										0.00%	2.00%		0.00%
Other, net										1,218,000	541,000		172,000
Other, net, percent										2.00%	0.00%		0.00%
Income tax expense (benefit)	$9,167,000	$9,605,000	$8,643,000	$8,796,000	$7,911,000		$6,734,000	$7,414,000	$4,935,000	$36,211,000	$26,994,000		$17,562,000
Income tax provision (benefit), percent										31.00%	31.00%		27.00%
[1]	Reclassified to conform to current period presentation. The reclassification was limited to including previously reported amounts for net operating losses and credit carryforwards, which had been included in the row for other deferred tax assets into a separate row.

Regulatory_Capital_Requirement2

Regulatory Capital Requirements (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013
In Thousands, unless otherwise specified
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Total Capital, Actual Amount	$890,029	$760,349
Total Capital (to risk-weighted assets), Ratio	14.13%	14.68%
Total Capital For Capital Adequacy Purposes, Amount	503,989	414,300
Total Capital (to risk-weighted assets), For Capital Adequacy Purposes, Ratio	8.00%	8.00%
Tier 1 Capital, Actual Amount	817,805	695,489
Tier 1 Capital (to risk-weighted assets), Ratio	12.98%	13.43%
Tier 1 Capital For Capital Adequacy Purposes, Amount	251,995	207,150
Tier 1 Capital (to risk-weighted assets) For Capital Adequacy Purposes, Ratio	4.00%	4.00%
Tier 1 Capital, Actual Amount	817,805	695,489
Tier 1 Capital (to average assets), Ratio	10.57%	10.19%
Tier 1 Capital For Capital Adequacy Purposes, Amount	309,579	272,891
Tier 1 Capital (to average assets) For Capital Adequacy Purposes, Ratio	4.00%	4.00%
Parent Company [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Total Capital, Actual Amount	860,755	700,099
Total Capital (to risk-weighted assets), Ratio	13.67%	13.52%
Total Capital For Capital Adequacy Purposes, Amount	503,852	414,238
Total Capital (to risk-weighted assets), For Capital Adequacy Purposes, Ratio	8.00%	8.00%
Total Capital To Be Well Capitalized Under Prompt Corrective Action Provision, Amount	629,816	517,797
Total Capital (to risk-weighted assets) To Be Well Capitalized Under Prompt Corrective Action Provision	10.00%	10.00%
Tier 1 Capital, Actual Amount	788,531	635,248
Tier 1 Capital (to risk-weighted assets), Ratio	12.52%	12.27%
Tier 1 Capital For Capital Adequacy Purposes, Amount	251,926	207,119
Tier 1 Capital (to risk-weighted assets) For Capital Adequacy Purposes, Ratio	4.00%	4.00%
Tier 1 Capital To Be Well Capitalized Under Prompt Corrective Action Provision, Amount	377,889	310,678
Tier 1 Capital (to risk-weighted assets) To Be Well Capitalized Under Prompt Corrective Action Provision, Ratio	6.00%	6.00%
Tier 1 Capital, Actual Amount	788,531	635,248
Tier 1 Capital (to average assets), Ratio	9.79%	9.29%
Tier 1 Capital For Capital Adequacy Purposes, Amount	322,029	273,560
Tier 1 Capital (to average assets) For Capital Adequacy Purposes, Ratio	4.00%	4.00%
Tier 1 Capital To Be Well Capitalized Under Prompt Corrective Provision, Amount	$402,537	$341,950
Tier 1 Capital (to average assets) To Be Well Capitalized Under Prompt Corrective Provision, Ratio	5.00%	5.00%

Branch_Sales_Details

Branch Sales (Details) (USD $)	0 Months Ended	12 Months Ended
	Aug. 23, 2014	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Aug. 23, 2014
					location
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Deposit Premium Percentage	2.35%				2.35%
Disposal Group, Not Discontinued Operation, Gain (Loss) on Disposal		$565,000	$0	$0
Disposal Date	23-Aug-14
Branch sales, number of branches sold in disposal group	3				3
Deposits [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Disposal group, branch sale, Deposits transferred	22,200,000				22,200,000
Disposal Group, Not Discontinued Operation, Gain (Loss) on Disposal	565,000
Loans Receivable [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Disposal group, branch sale, loans transferred	1,100,000				1,100,000
Property, Plant and Equipment [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Disposal group, branch sale, premises and equipment transferred	3,800,000				3,800,000
Disposal Group, Not Discontinued Operation, Gain (Loss) on Disposal	50,000

Parent_Company_Financial_Infor2

Parent Company Financial Information (Condensed Statements of Income) (Details) (USD $)	3 Months Ended								12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Income
Interest-earning deposits									$179		$355		$854
Expense
Compensation and employee benefits									130,864		125,432		85,434
Other borrowings									593		734		479
Other expense									27,045	[1]	29,962	[1]	20,961	[1]
Income before income taxes	28,087	31,188	29,870	28,640	27,884	20,010	22,005	17,111	117,785		87,010		63,705
Income tax expense (benefit)	9,167	9,605	8,643	8,796	7,911	6,734	7,414	4,935	36,211		26,994		17,562
Net income (loss)	18,920	21,583	21,227	19,844	19,973	13,276	14,591	12,176	81,574		60,016		46,143
Parent Company [Member]
Income
Dividend from banking subsidiaries									16,200		183,000		48,950
Interest-earning deposits									25		68		153
Other income									10		7		0
Total Income									16,235		183,075		49,103
Expense
Compensation and employee benefits									530		658		182
Other borrowings									83		258		0
Other expense									1,433		4,162		1,193
Total Expenses									2,046		5,078		1,375
Income before income taxes									14,189		177,997		47,728
Income tax expense (benefit)									-704		-1,552		-435
Income before equity in undistributed net income (loss) of subsidiaries									14,893		179,549		48,163
Equity in undistributed net income (loss) of subsidiaries									66,681		-119,533		-2,020
Net income (loss)									$81,574		$60,016		$46,143
[1]	(1) Reclassified to conform to the current period’s presentation. The reclassification was limited to removing the separate line item for FDIC clawback liability expense within noninterest expense and including the prior period activity in the line item for other noninterest expense as well as removing the separate line item for provision for losses on covered loans and including the prior period activity in the line item for provision for loan and lease losses.

Parent_Company_Financial_Infor3

Parent Company Financial Information (Condensed Balance Sheets) (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
In Thousands, unless otherwise specified
Assets
Cash and due from banks	$171,221	$165,030
Interest-earning deposits	16,949	14,531
Total cash and cash equivalents	188,170	179,561	513,926	294,289
Other assets	231,877	217,289
Total Assets	8,578,846	7,161,582
Liabilities and Shareholders’ Equity
Other borrowings	8,248	0
Other liabilities	96,053	87,252
Total liabilities	7,350,671	6,108,333
Shareholders’ equity	1,228,175	1,053,249	764,008	759,338
Total liabilities and shareholders' equity	8,578,846	7,161,582
Parent Company [Member]
Assets
Cash and due from banks	10,322	3,006
Interest-earning deposits	12,274	50,678
Total cash and cash equivalents	22,596	53,684	86,644	75,234
Other assets	5,273	1,952
Total Assets	1,240,363	1,053,675
Liabilities and Shareholders’ Equity
Other borrowings	8,248	0
Other liabilities	3,940	426
Total liabilities	12,188	426
Shareholders’ equity	1,228,175	1,053,249
Total liabilities and shareholders' equity	1,240,363	1,053,675
Banking Subsidiaries [Member] | Parent Company [Member]
Assets
Investment in subsidiaries	1,207,143	993,002
Other Subsidiaries [Member] | Parent Company [Member]
Assets
Investment in subsidiaries	$5,351	$5,037

Parent_Company_Financial_Infor4

Parent Company Financial Information (Condensed Statements of Cash Flows) (Details) (USD $)	12 Months Ended
In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Condensed Financial Statements, Captions [Line Items]
Proceeds from Warrant Exercises	$5,000	$0	$0
Operating Activities
Net Income (Loss)	81,574	60,016	46,143
Adjustments to reconcile net income to net cash provided by operating activities:
Stock-based compensation expense	2,859	2,844	1,622
Net cash provided by operating activities	137,618	79,636	134,899
Net cash acquired in business combinations	32,255	-154,170	0
Investing Activities
Net cash provided by investing activities	-521,961	-281,060	8,403
Financing Activities
Payments of Ordinary Dividends, Preferred Stock and Preference Stock	-96	-32	0
Cash dividends paid	-49,494	-19,858	-38,824
Purchase and retirement of common stock	-622	-429	0
Proceeds from exercise of stock options	929	1,092	713
Excess tax benefit from stock-based compensation	205	1,203	0
Net cash provided by financing activities	392,952	-132,941	76,335
Increase (decrease) in cash and cash equivalents	8,609	-334,365	219,637
Cash and cash equivalents at beginning of period	179,561	513,926	294,289
Cash and cash equivalents at end of period	188,170	179,561	513,926
Parent Company [Member]
Condensed Financial Statements, Captions [Line Items]
Proceeds from Warrant Exercises	5,000	0	0
Operating Activities
Net Income (Loss)	81,574	60,016	46,143
Adjustments to reconcile net income to net cash provided by operating activities:
Equity in undistributed earnings of subsidiaries	-66,681	119,533	2,020
Stock-based compensation expense	2,859	2,844	1,622
Net changes in other assets and liabilities	-403	6,830	-264
Net cash provided by operating activities	17,349	189,223	49,521
Net cash acquired in business combinations	10,277	-53,159	0
Investing Activities
Net cash provided by investing activities	10,277	-53,159	0
Financing Activities
Payments of Ordinary Dividends, Preferred Stock and Preference Stock	-96	-32	0
Cash dividends paid	-49,494	-19,858	-38,824
Repayment of long-term subordinated debt	-14,636	-51,000	0
Purchase and retirement of common stock	-622	-429	0
Proceeds from exercise of stock options	929	1,092	713
Downstream stock offering proceeds to the Bank	0	-100,000	0
Excess tax benefit from stock-based compensation	205	1,203	0
Net cash provided by financing activities	-58,714	-169,024	-38,111
Increase (decrease) in cash and cash equivalents	-31,088	-32,960	11,410
Cash and cash equivalents at beginning of period	53,684	86,644	75,234
Cash and cash equivalents at end of period	$22,596	$53,684	$86,644

Summary_Of_Quarterly_Financial2

Summary Of Quarterly Financial Information (Unaudited) (Details) (USD $)	3 Months Ended								12 Months Ended
In Thousands, except Per Share data, unless otherwise specified	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Quarterly Financial Information Disclosure [Abstract]
Total interest income	$79,897	$77,133	$76,087	$74,925	$78,307	$81,599	$82,268	$54,761	$308,042	$296,935	$248,504
Total interest expense	1,133	913	963	985	1,098	1,184	2,279	1,279	3,994	5,840	9,577
Net Interest Income	78,764	76,220	75,124	73,940	77,209	80,415	79,989	53,482	304,048	291,095	238,927
Provision (recapture) for loan and lease losses	1,708	980	2,117	1,922	-3,682	3,313	288	-20	6,727	-101	39,367
Noninterest income (loss)	15,185	15,930	14,627	14,008	10,612	7,622	6,808	1,658	59,750	26,700	27,058
Noninterest expense	64,154	59,982	57,764	57,386	63,619	64,714	64,504	38,049	239,286	230,886	162,913
Income before income taxes	28,087	31,188	29,870	28,640	27,884	20,010	22,005	17,111	117,785	87,010	63,705
Income tax expense (benefit)	9,167	9,605	8,643	8,796	7,911	6,734	7,414	4,935	36,211	26,994	17,562
Net income (loss)	$18,920	$21,583	$21,227	$19,844	$19,973	$13,276	$14,591	$12,176	$81,574	$60,016	$46,143
Per Common Share
Earnings (basic)	$0.34	$0.41	$0.40	$0.38	$0.39	$0.26	$0.28	$0.31	$1.53	$1.24	$1.16
Earnings (diluted)	$0.34	$0.41	$0.40	$0.37	$0.38	$0.25	$0.28	$0.31	$1.52	$1.21	$1.16