Contingencies (Details) (USD $) In Millions, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Commitments and Contingencies
Maximum liability under indemnity in connection with liquidation of an investment acquired	$ 23.0
Letters of Credit
Commitments and Contingencies
Commitments	679.0	733.5
Standby letters of credit, included within letters of credit
Commitments and Contingencies
Commitments	574.3	617.3
Commercial letters of credit, including within letters of credit
Commitments and Contingencies
Commitments	$ 104.7	$ 116.2