Investment Securities (Details 5) (USD $) In Millions, unless otherwise specified	6 Months Ended
	Jun. 30, 2012	Jun. 30, 2012 Hedge and private equity funds included in other long-term investments	Dec. 31, 2011 Hedge and private equity funds included in other long-term investments	Jun. 30, 2012 Hedge funds Entity	Jun. 30, 2012 Hedge funds	Dec. 31, 2011 Hedge funds	Jun. 30, 2012 Hedge funds 30-59 days notice	Jun. 30, 2012 Hedge funds 60-89 days notice	Jun. 30, 2012 Hedge funds 90-119 days notice	Jun. 30, 2012 Hedge funds 120+ days notice	Jun. 30, 2012 Hedge funds Monthly	Jun. 30, 2012 Hedge funds Monthly 30-59 days notice	Jun. 30, 2012 Hedge funds Monthly 60-89 days notice	Jun. 30, 2012 Hedge funds Monthly 90-119 days notice	Jun. 30, 2012 Hedge funds Monthly 120+ days notice	Jun. 30, 2012 Hedge funds Semi-annual	Jun. 30, 2012 Hedge funds Semi-annual 30-59 days notice	Jun. 30, 2012 Hedge funds Semi-annual 60-89 days notice	Jun. 30, 2012 Hedge funds Semi-annual 90-119 days notice	Jun. 30, 2012 Hedge funds Semi-annual 120+ days notice	Jun. 30, 2012 Hedge funds Quarterly	Jun. 30, 2012 Hedge funds Quarterly 30-59 days notice	Jun. 30, 2012 Hedge funds Quarterly 60-89 days notice	Jun. 30, 2012 Hedge funds Quarterly 90-119 days notice	Jun. 30, 2012 Hedge funds Quarterly 120+ days notice	Jun. 30, 2012 Hedge funds Annual	Jun. 30, 2012 Hedge funds Annual 30-59 days notice	Jun. 30, 2012 Hedge funds Annual 60-89 days notice	Jun. 30, 2012 Hedge funds Annual 90-119 days notice	Jun. 30, 2012 Hedge funds Annual 120+ days notice	Jun. 30, 2012 Long/short equity Hedge funds	Dec. 31, 2011 Long/short equity Hedge funds	Jun. 30, 2012 Long/short credit & distressed Hedge funds	Dec. 31, 2011 Long/short credit & distressed Hedge funds	Jun. 30, 2012 Long diversified strategies Hedge funds	Dec. 31, 2011 Long diversified strategies Hedge funds	Jun. 30, 2012 Long/short equity REIT Hedge funds	Dec. 31, 2011 Long/short equity REIT Hedge funds	Jun. 30, 2012 Long/short equity activist Hedge funds	Dec. 31, 2011 Long/short equity activist Hedge funds	Jun. 30, 2012 Long bank loan Hedge funds	Dec. 31, 2011 Long bank loan Hedge funds	Jun. 30, 2012 Private equity funds Entity	Jun. 30, 2012 Private equity funds 1-3 years	Jun. 30, 2012 Private equity funds 3-5 years	Jun. 30, 2012 Private equity funds 5-10 years	Jun. 30, 2012 Private equity funds >10 years	Jun. 30, 2012 Private equity funds	Dec. 31, 2011 Private equity funds	Jun. 30, 2012 Multi-sector Private equity funds	Dec. 31, 2011 Multi-sector Private equity funds	Jun. 30, 2012 Energy infrastructure and services Private equity funds	Dec. 31, 2011 Energy infrastructure and services Private equity funds	Jun. 30, 2012 Distressed residential real estate Private equity funds	Dec. 31, 2011 Distressed residential real estate Private equity funds	Jun. 30, 2012 Real estate Private equity funds	Dec. 31, 2011 Real estate Private equity funds	Jun. 30, 2012 Private equity secondaries Private equity funds	Dec. 31, 2011 Private equity secondaries Private equity funds	Jun. 30, 2012 International multi-sector, Europe Private equity funds	Dec. 31, 2011 International multi-sector, Europe Private equity funds	Jun. 30, 2012 Manufacturing/Industrial Private equity funds	Dec. 31, 2011 Manufacturing/Industrial Private equity funds	Jun. 30, 2012 Healthcare Private equity funds	Dec. 31, 2011 Healthcare Private equity funds	Jun. 30, 2012 International multi-sector, Asia Private equity funds	Dec. 31, 2011 International multi-sector, Asia Private equity funds	Jun. 30, 2012 Insurance Private equity funds	Dec. 31, 2011 Insurance Private equity funds	Jun. 30, 2012 Venture capital fund Private equity funds	Dec. 31, 2011 Venture capital fund Private equity funds
Investment securities
Number of investments				17																																							34
Largest single fund investment		$ 21.5
Other long-term investments		244.4	254.2	116.4	116.4	125.3	29.7	36.8	28.2	21.7	6.7	0	0	0	6.7	20.0	0	5.4	0	14.6	78.4	26.8	31.4	20.2	0	11.3	2.9	0	8.0	0.4	52.1	48.8	33.0	32.3	2.9	16.9	14.6	14.5	13.4	12.3	0.4	0.5	128.0	33.9	15.4	72.3	6.4	128.0	128.9	29.2	26.9	30.3	28.0	21.5	27.4	12.2	9.5	10.9	11.3	5.2	7.8	6.4	6.2	3.3	2.3	3.3	3.6	3.2	3.5	2.5	2.4
Unfunded Commitments		78.4	81.5		0	0																									0	0	0	0	0	0	0	0	0	0	0	0						78.4	81.5	6.7	8.2	9.4	9.9	0	0	3.3	3.3	3.4	4.0	4.7	4.7	0	0	6.4	7.0	2.7	2.6	41.3	41.3	0.5	0.5
Distributions outstanding				3.2
Redemption requests				14.0
Maximum percentage of price difference provided by pricing services	5.00%
Maximum price difference provided by pricing services	$ 1.0