Acquisition of KBW, Inc. (Narrative) (Details) (USD $) Share data in Millions, except Per Share data, unless otherwise specified	0 Months Ended	12 Months Ended
	Feb. 15, 2013	Dec. 31, 2013
Business Acquisition [Line Items]
Goodwill recorded in business combination		$ 307,943,000
Fair value of awards issued as retention		30,600,000
KBW [Member]
Business Acquisition [Line Items]
Cash consideration per share	$ 8.00
Cash consideration per share before extraordinary dividend amount	$ 10.00
Extraordinary dividend	$ 2.00
Stock consideration, common stock	0.2143%
Goodwill recorded in business combination		288,300,000
Transaction costs		$ 9,800,000
KBW [Member] | Common Stock [Member]
Business Acquisition [Line Items]
Shares issued	6.7
KBW [Member] | Restricted Awards [Member]
Business Acquisition [Line Items]
Shares issued	2.2