Condensed Consolidated Statement of Comprehensive Income - USD ($) $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Statement of Comprehensive Income [Abstract]
Net income attributable to DST Systems, Inc.		$ 75.4	$ 53.0	$ 321.8	$ 111.1
Other comprehensive income (loss), net of tax and reclassifications to earnings, derived from:
Available-for-sale securities		(5.7)	(6.1)	(93.9)	(22.4)
Cash flow hedges		0.0	0.0	0.2	0.2
Foreign currency translation adjustments	[1]	6.9	(20.1)	53.1	(23.2)
Other comprehensive income (loss)		1.2	(26.2)	(40.6)	(45.4)
Comprehensive income		$ 76.6	$ 26.8	$ 281.2	$ 65.7

[1] Cumulative translation adjustments are inclusive of amounts derived from assets and liabilities held for sale.