Investment Securities (Restrictions on Redemption Frequency and Advance Notice Requirements) (Details) - Hedge funds $ in Millions	Dec. 31, 2015 USD ($)
Investment securities
Trading Securities, Other	$ 37.0
Distributions from inactive hedge funds	1.0
Outstanding redemptions	2.5
30-59 days notice
Investment securities
Trading Securities, Other	13.8
60-89 days notice
Investment securities
Trading Securities, Other	20.6
90-119 days notice
Investment securities
Trading Securities, Other	2.6
120 days notice
Investment securities
Trading Securities, Other	0.0
Monthly
Investment securities
Trading Securities, Other	0.0
Monthly | 30-59 days notice
Investment securities
Trading Securities, Other	0.0
Monthly | 60-89 days notice
Investment securities
Trading Securities, Other	0.0
Monthly | 90-119 days notice
Investment securities
Trading Securities, Other	0.0
Monthly | 120 days notice
Investment securities
Trading Securities, Other	0.0
Quarterly
Investment securities
Trading Securities, Other	13.8
Quarterly | 30-59 days notice
Investment securities
Trading Securities, Other	13.8
Quarterly | 60-89 days notice
Investment securities
Trading Securities, Other	0.0
Quarterly | 90-119 days notice
Investment securities
Trading Securities, Other	0.0
Quarterly | 120 days notice
Investment securities
Trading Securities, Other	0.0
Semi-annual
Investment securities
Trading Securities, Other	20.6
Semi-annual | 30-59 days notice
Investment securities
Trading Securities, Other	0.0
Semi-annual | 60-89 days notice
Investment securities
Trading Securities, Other	20.6
Semi-annual | 90-119 days notice
Investment securities
Trading Securities, Other	0.0
Semi-annual | 120 days notice
Investment securities
Trading Securities, Other	0.0
Annual
Investment securities
Trading Securities, Other	2.6
Annual | 30-59 days notice
Investment securities
Trading Securities, Other	0.0
Annual | 60-89 days notice
Investment securities
Trading Securities, Other	0.0
Annual | 90-119 days notice
Investment securities
Trading Securities, Other	2.6
Annual | 120 days notice
Investment securities
Trading Securities, Other	$ 0.0