Income Taxes (Details) - USD ($) $ 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
Pretax income (loss)
U.S.									$ 248.2	$ 451.9	$ 627.9
International									31.0	6.9	116.8
Income from continuing operations before income taxes and non-controlling interest	$ 81.4	$ 82.6	$ 56.6	$ 58.6	$ 76.9	$ 82.0	$ 151.2	$ 148.7	279.2	458.8	744.7
Current
Federal									57.7	147.4	207.8
State and local									11.4	10.2	(23.8)
International									15.0	7.1	(1.5)
Total current									84.1	164.7	182.5
Deferred
Federal									19.9	(13.5)	5.3
State and local									(1.9)	0.5	(1.3)
International									(1.0)	(2.5)	(2.6)
Total deferred									17.0	(15.5)	1.4
Total provision for income taxes	27.3	31.6	22.1	20.1	22.0	15.9	55.7	55.6	101.1	149.2	183.9
Differences between the Company's effective income tax rate and the U.S. federal income tax statutory rate
Provision for income taxes using the statutory rate in effect									97.7	160.6	260.7
Tax effect of:
State and local income taxes, net									5.9	4.3	8.6
International income taxes, net									2.5	(1.0)	(1.9)
Gain on sale of DST Global Solutions Ltd.									0.0	0.0	(33.6)
Earnings of U.S. unconsolidated affiliates									(2.3)	(1.5)	(1.4)
Valuation allowance (reversal), net									(0.9)	1.2	0.8
Tax credits									(5.0)	(7.7)	(7.9)
Uncertain tax positions (reversal), net									1.7	(7.9)	(30.8)
Dividend received deduction									(0.8)	(1.2)	(2.6)
Domestic production activities deduction									(1.7)	(0.1)	(3.1)
Repatriation									1.0	1.9	0.7
Gain on share repurchase									0.0	0.0	(6.3)
Other									3.0	0.6	0.7
Total provision for income taxes	$ 27.3	$ 31.6	$ 22.1	$ 20.1	$ 22.0	$ 15.9	$ 55.7	$ 55.6	$ 101.1	$ 149.2	$ 183.9
Effective tax rate (as a percent)									36.20%	32.50%	24.70%
Statutory federal tax rate (as a percent)									35.00%	35.00%	35.00%