Acquisitions (Narrative) (Details) (USD $) Share data in Millions, except Per Share data, unless otherwise specified	0 Months Ended	12 Months Ended		0 Months Ended	1 Months Ended	0 Months Ended
	Feb. 15, 2013	Dec. 31, 2014	Dec. 31, 2013	Nov. 07, 2014	Jul. 31, 2014	Nov. 01, 2011	Apr. 03, 2014	Oct. 31, 2013	Nov. 30, 2014	Nov. 30, 2013
Business Acquisition [Line Items]
Goodwill		$ 795,026,000	$ 727,336,000
Bargain purchase gain			7,566,000
Stock consideration, common stock	0.2143
Goodwill recorded in business combination		67,690,000
Merchant Capital LLC [Member]
Business Acquisition [Line Items]
Goodwill		15,000,000
1919 Investment Counsel And Trust Company NA [Member]
Business Acquisition [Line Items]
Goodwill				13,800,000
Fair value of awards issued as retention				11,200,000
1919 Investment Counsel And Trust Company NA [Member] | Customer Relationships [Member]
Business Acquisition [Line Items]
Identifiable intangible assets				6,700,000
Oriel Securities [Member]
Business Acquisition [Line Items]
Goodwill					18,700,000
Fair value of awards issued as retention					6,800,000
Oriel Securities [Member] | Trade Names [Member]
Business Acquisition [Line Items]
Identifiable intangible assets					1,900,000
Oriel Securities [Member] | Non-Compete Agreements [Member]
Business Acquisition [Line Items]
Identifiable intangible assets					1,400,000
De La Rosa & Co. [Member]
Business Acquisition [Line Items]
Goodwill							17,400,000
De La Rosa & Co. [Member] | Customer Relationships [Member]
Business Acquisition [Line Items]
Identifiable intangible assets							200,000
De La Rosa & Co. [Member] | Trade Names [Member]
Business Acquisition [Line Items]
Identifiable intangible assets							1,800,000
Acacia Federal Savings Bank [Member]
Business Acquisition [Line Items]
Loans acquired in acquisition								337,100,000
Other assets acquired								180,400,000
Deposits assumed								435,400,000
Other liabilities assumed								10,000,000
Bargain purchase gain			7,600,000
Ziegler Lotsoff Capital Management, LLC [Member]
Business Acquisition [Line Items]
Goodwill									6,800,000
Ziegler Lotsoff Capital Management, LLC [Member] | Customer Relationships [Member]
Business Acquisition [Line Items]
Identifiable intangible assets										3,400,000
Ziegler Lotsoff Capital Management, LLC [Member] | Trade Names [Member]
Business Acquisition [Line Items]
Identifiable intangible assets										100,000
KBW [Member]
Business Acquisition [Line Items]
Goodwill	288,300,000
Fair value of awards issued as retention	30,600,000
Cash consideration per share	8.00
Cash consideration per share before extraordinary dividend amount	10.00
Extraordinary dividend	2.00
Expected cash consideration	253,000,000
Transaction costs	9,800,000
Fair value of awards issued as retention		30,600,000
KBW [Member] | Customer Relationships [Member]
Business Acquisition [Line Items]
Identifiable intangible assets	11,000,000
KBW [Member] | Trade Names [Member]
Business Acquisition [Line Items]
Identifiable intangible assets	9,000,000
KBW [Member] | Investment Banking Backlog [Member]
Business Acquisition [Line Items]
Identifiable intangible assets	4,000,000
KBW [Member] | Common Stock [Member]
Business Acquisition [Line Items]
Stock issued in conjunction with merger	6.7
KBW [Member] | Restricted Stock [Member]
Business Acquisition [Line Items]
Stock issued in conjunction with merger	2.2
Stone & Youngberg LLC [Member]
Business Acquisition [Line Items]
Consideration to be paid in installments						24,000,000
Number of years in installment plan						3 years
Period of contingent consideration						5 years
Maximum earn-out						25,000,000
Liability for earn-out payments and installment payments		$ 8,000,000	$ 16,800,000