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The amount of goodwill arising from a business combination that is expected to be deductible for tax purposes.

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The pro forma net Income or Loss for the period as if the business combination or combinations had been completed at the beginning of a period.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
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This element represents acquisition-related costs incurred to effect a business combination which costs have been expensed during the period. Such costs include finder's fees; advisory, legal, accounting, valuation, and other professional or consulting fees; general administrative costs, including the costs of maintaining an internal acquisitions department; and may include costs of registering and issuing debt and equity securities.

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- References

No definition available.

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Amount of consideration transferred, consisting of acquisition-date fair value of assets transferred by the acquirer, liabilities incurred by the acquirer, and equity interest issued by the acquirer.

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Amount of assets acquired at the acquisition date.

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Amount of lease obligation assumed in business combination.

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Data Type:	xbrli:monetaryItemType
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Period Type:	instant

Amount of currency on hand as well as demand deposits with banks or financial institutions, acquired at the acquisition date. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.

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Period Type:	instant

Amount of deferred tax asset attributable to deductible temporary differences and carryforwards acquired at the acquisition date.

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Data Type:	xbrli:monetaryItemType
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Period Type:	instant

The amount of identifiable intangible assets recognized as of the acquisition date.

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Amount of liabilities assumed at the acquisition date.

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Amount recognized as of the acquisition date for the identifiable assets acquired in excess of (less than) the aggregate liabilities assumed.

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Amount of long-term debt due after one year or the normal operating cycle, if longer, assumed at the acquisition date.

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Amount of other liabilities due after one year or the normal operating cycle, if longer, assumed at the acquisition date.

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Amount of other assets expected to be realized or consumed after one year or the normal operating cycle, if longer, acquired at the acquisition date.

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The amount of property, plant, and equipment recognized as of the acquisition date.

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Useful life of finite-lived intangible assets, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

No definition available.

Name:	us-gaap_FiniteLivedIntangibleAssetUsefulLife
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
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Period Type:	duration

Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(10)(1))
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The cash outflow associated with the acquisition of business during the period. The cash portion only of the acquisition price.

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-Publisher FASB
-Name Accounting Standards Codification
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Business Acquisition, Pro Forma Interest Income

No definition available.

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Business Acquisition, Pro Forma Non-interest Income

No definition available.

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Business Combination, Elimination of Pre-existing debt and other

No definition available.

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Period Type:	instant

This element represents the amount of any measurement period adjustment (as defined) realized during the reporting period to servicing rights assets acquired in connection with a business combination for which the initial accounting was incomplete

No definition available.

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Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Liability for Loans Eligible for Repurchase

No definition available.

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Data Type:	xbrli:monetaryItemType
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Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Loans Eligible for Repurchase

No definition available.

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Namespace Prefix:	wal_
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Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Loans Held for Sale

No definition available.

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Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Operating Right of use Asset

No definition available.

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Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Servicing Assets

No definition available.