Equity (Details 3) (USD $) In Millions, except Share data, unless otherwise specified	0 Months Ended	1 Months Ended	3 Months Ended				12 Months Ended
	Jan. 30, 2013	Nov. 30, 2011	Dec. 31, 2012	Mar. 31, 2012	Sep. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011 plan	Dec. 31, 2010
Stock repurchases
Amount authorized under new share repurchase plan	$ 250.0
Shares available under existing share repurchase plan	715,700
Additional number of shares authorized to be repurchased		2,000,000
Number of plans with brokers or banks for pre-authorized purchases within defined limits								1
Aggregate repurchase price of common stock							73.7	135.4	116.6
Common stock repurchased (in shares)							1,300,000	3,000,000	2,900,000
Amount of share withholdings for option exercises							30.8	39.3	21.1
Common stock held in treasury			51,100,000				51,100,000	51,200,000
Dividends
Cash dividend paid (in dollars per share)			$ 0.40	$ 0.40	$ 0.35	$ 0.35	$ 0.80	$ 0.70	$ 0.60
Aggregate cash dividend paid							36.0	31.6	28.2
Total dividend							37.6
Cash dividend declared (in dollars per share)	$ 0.30
One of DST's unconsolidated affiliates
Unconsolidated affiliates
Number of unconsolidated affiliates with an interest rate swap			1				1
Unconsolidated affiliate's interest rate swap liability, fair value			73.5				73.5	73.0	47.7
Equity method investments ownership percentage			50.00%				50.00%
Proportionate share in unconsolidated affiliate's interest rate swap liability			36.8				36.8	36.5	23.9
Amount of entity's proportionate share of the interest rate swap liability recorded at the end of the reporting period									$ 2.0