Acquisitions (Details Textual) - USD ($) $ / shares in Units, $ in Thousands				3 Months Ended								12 Months Ended
	Oct. 06, 2015	Apr. 07, 2014	May. 31, 2013	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Business Acquisition [Line Items]
Common Stock, Par or Stated Value Per Share				$ 0.01				$ 0.01				$ 0.01	$ 0.01
Business Combination, Step Acquisition, Equity Interest in Acquiree, Including Subsequent Acquisition, Percentage	15.00%
Goodwill				$ 2,176,291				$ 1,720,479				$ 2,176,291	$ 1,720,479	$ 208,743	$ 79,866
Acquisition, integration and reorganization costs				$ 107,849	$ 84,871	$ 86,716	$ 82,024	$ 81,986	$ 84,903	$ 82,461	$ 49,825	$ 21,247	101,016	40,812
Expense incurred due to awarded shares of restricted common stock vested due to the triggering of the change of control provision contained within the 2003 Plan													$ 26,100	$ 12,400
Square 1 Financial, Inc. [Member]
Business Acquisition [Line Items]
Business Acquisition, Effective Date of Acquisition	Oct. 06, 2015
Business Acquisition Shares Receivable By Stockholders Of Acquiree Ratio	0.5597
Business Acquisition, Equity Interest Issued or Issuable, Value Assigned	$ 17,800
Common Stock, Value, Outstanding	$ 815,000
Common Stock, Par or Stated Value Per Share	$ 43.97
Goodwill	$ 447,911
Capitalsource, Inc. [Member]
Business Acquisition [Line Items]
Business Acquisition, Effective Date of Acquisition		Apr. 07, 2014
Goodwill		$ 1,526,282
First California Financial Group, Inc. [Member]
Business Acquisition [Line Items]
Business Acquisition, Effective Date of Acquisition			May 31, 2013
Goodwill			$ 129,070
Shares Of Common Stock [Member] | Square 1 Financial, Inc. [Member]
Business Acquisition [Line Items]
Stock Issued During Period, Shares, New Issues	18,100,000
CapitalSource Inc. [Member]
Business Acquisition [Line Items]
Business Acquisition, Effective Date of Acquisition												Apr. 07, 2014