Acquisitions (Details Textual) - CU Bancorp [Member] - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2018	Oct. 20, 2017
Business Combination Recognized Identifiable Assets Acquired And Liabilities Assumed Loans And Leases Receivable Net Reported Amount Covered And Not Covered		$ 2,100.0
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Liabilities		2,800.0
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Assets		3,500.0
CU Bancorp [Member]
Goodwill, Acquired During Period	$ 374.7
Core Deposits [Member]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Liabilities		$ 2,700.0

Amount after allowance and deduction of deferred interest and fees, unamortized costs and premiums over and discounts from face amounts, of loans and leases held in portfolio, including loans and leases covered under loss sharing agreements, acquired at the acquisition date.

No definition available.

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- Definition

Amount of assets acquired at the acquisition date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=84161108&loc=d3e4845-128472

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- Definition

Amount of liabilities assumed at the acquisition date.

+ References

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- Definition

Amount of increase in asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized resulting from a business combination.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=35741047&loc=d3e13816-109267

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