Organization (Details) (USD $)	3 Months Ended
	Mar. 31, 2015 bank_branch	Dec. 31, 2014	Mar. 31, 2014
General Introduction [Abstract]
Total assets	$ 16,643,940,000	$ 16,234,605,000	$ 6,517,853,000
Loans and Leases Receivable Gross Carrying Amount Covered And Noncovered	12,302,292,000	11,904,684,000
Total deposits	11,934,175,000	11,755,128,000	5,369,408,000
Total stockholders' equity	3,533,361,000	3,506,230,000
Number Of Branches	80
Number of Businesses Acquired	27
Start of Acquisition Activities	May 01, 2000
Square 1 Financial, Inc. Acquisition Plan [Abstract]
Common Stock, Par or Stated Value Per Share	$ 0.01	$ 0.01
Square 1 Financial, Inc. [Member]
Square 1 Financial, Inc. Acquisition Plan [Abstract]
Business Acquisition, Date of Acquisition Agreement	Mar. 02, 2015
Business Combination, Contingent Consideration, Liability	849,000,000
Business Acquisition Shares Receivable By Stockholders Of Acquiree Ratio	0.5997
Business Acquisition, Share Price	$ 27.49
Common Stock, Par or Stated Value Per Share	$ 45.84
Consideration valuation date	February 27, 2015
Consolidated Total Assets Proforma Upon Acquisition	19,800,000,000
Number of Branches Upon Acquisition	80
Retained Earnings [Member]
General Introduction [Abstract]
Total stockholders' equity	(212,633,000)	(285,712,000)
Other Organization Information [Abstract]
Cumulative Effect of Prospective Application of New Accounting Principle	$ (195,000)