Condensed Consolidated Statement of Income - USD ($) shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Income Statement [Abstract]
Operating revenues	$ 524.8	$ 365.5	$ 1,534.0	$ 1,100.7
Out-of-pocket reimbursements	37.8	21.2	90.3	57.2
Total revenues	562.6	386.7	1,624.3	1,157.9
Costs and expenses	472.1	289.6	1,323.7	916.9
Depreciation and amortization	34.7	22.8	92.7	69.1
Operating income	55.8	74.3	207.9	171.9
Interest expense	(6.9)	(5.4)	(19.7)	(18.0)
Other income, net	8.7	6.7	217.2	20.0
Equity in earnings of unconsolidated affiliates	4.2	7.0	27.3	23.9
Income from continuing operations before income taxes and non-controlling interest	61.8	82.6	432.7	197.8
Income taxes	13.0	31.6	66.3	73.8
Income from continuing operations before non-controlling interest	48.8	51.0	366.4	124.0
Income (loss) from discontinued operations, net of tax	(0.3)	222.8	4.5	260.0
Net income	48.5	273.8	370.9	384.0
Net (income) loss attributable to non-controlling interest	0.0	(0.5)	(0.6)	0.4
Net income attributable to DST Systems, Inc.	$ 48.5	$ 273.3	$ 370.3	$ 384.4
Weighted average common shares outstanding	60.7	65.4	61.9	66.5
Weighted average diluted shares outstanding	61.6	66.1	62.7	67.3
Basic earnings per share
Continuing operations attributable to DST Systems, Inc., per basic share	$ 0.81	$ 0.77	$ 5.91	$ 1.88
Discontinued operations, per basic share	(0.01)	3.41	0.07	3.90
Basic earnings per share	0.80	4.18	5.98	5.78
Diluted earnings per share
Continuing operations attributable to DST Systems, Inc., per diluted share	0.79	0.76	5.84	1.85
Discontinued operation, per diluted share	0.00	3.37	0.07	3.87
Diluted earnings per share	0.79	4.13	5.91	5.72
Cash dividends per share of common stock	$ 0.18	$ 0.17	$ 0.54	$ 0.5