Equity (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016		Dec. 31, 2015		Dec. 31, 2014
Equity [Abstract]
Income from continuing operations attributable to DST Systems, Inc.									$ 179.0		$ 309.7		$ 560.8
Income from discontinued operations, net of tax	$ (11.7)	$ 222.8	$ 18.7	$ 18.5	$ 12.8	$ 9.0	$ 12.0	$ 14.7	248.3		48.5		32.5
Net income attributable to DST Systems, Inc.	$ 42.9	$ 273.3	$ 53.0	$ 58.1	$ 67.8	$ 75.1	$ 107.5	$ 107.8	$ 427.3		$ 358.2		$ 593.3
Weighted average common shares outstanding	32.1	32.7	33.3	33.8	34.5	35.7	36.6	37.2	33.0		36.0		40.0
Incremental shares from restricted stock units, stock options and convertible debentures									0.3		0.4		0.5
Weighted average diluted shares outstanding	32.5	33.0	33.6	34.3	35.0	36.2	37.0	37.6	33.3		36.4		40.5
Basic earnings per share
Continuing operations attributable to DST Systems, Inc., per basic share (in dollars per share)	$ 1.70	$ 1.54	$ 1.03	$ 1.17	$ 1.59	$ 1.85	$ 2.61	$ 2.50	$ 5.43	[1]	$ 8.60	[1]	$ 14.01
Discontinued operation, per basic share (in dollars per share)	(0.36)	6.81	0.56	0.55	0.37	0.25	0.33	0.40	7.53	[1]	1.35	[1]	0.81
Basic earnings per share (in dollars per share)	1.34	8.35	1.59	1.72	1.96	2.10	2.94	2.90	12.96	[1]	9.95	[1]	14.82
Diluted earnings per share
Continuing operations attributable to DST Systems, Inc., per diluted share (in dollars per share)	1.68	1.53	1.03	1.16	1.57	1.83	2.58	2.48	5.37	[1]	8.50	[1]	13.86
Discontinued operation, per diluted share (in dollars per share)	(0.36)	6.75	0.55	0.54	0.37	0.25	0.33	0.39	7.45	[1]	1.33	[1]	0.80
Diluted earnings per share (in dollars per share)	$ 1.32	$ 8.28	$ 1.58	$ 1.70	$ 1.94	$ 2.08	$ 2.91	$ 2.87	$ 12.82	[1]	$ 9.83	[1]	$ 14.66
Shares outstanding	32.0				34.3				32.0		34.3
Shares from options to purchase common stock, excluded from diluted earnings per share calculation									0.0		0.0
Preferred stock, shares authorized	10.0				10.0				10.0		10.0

[1] Earnings per share are computed independently for each of the quarters presented. Accordingly, the accumulation of quarterly earnings per share may not equal the total computed for the year.