Segment Information (Details) $ in Millions	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2017 USD ($)	Jun. 30, 2016 USD ($)	Jun. 30, 2017 USD ($)	Jun. 30, 2016 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Segment Reporting [Abstract]
Number of operating segments			3
Summary of financial information of segments [Line Items]
Total assets	$ 2,964.9		$ 2,964.9		$ 2,771.8
Operating revenues	629.4	$ 373.9	1,009.2	$ 735.2
Out-of-pocket reimbursements	26.8	16.6	52.5	36.0	82.3	$ 69.0
Total revenues	656.2	390.5	1,061.7	771.2	1,556.7	1,474.0
Costs and expenses	525.2	320.4	851.6	627.3	1,213.4	1,150.2
Depreciation and amortization	34.8	24.2	58.0	46.3	96.0	91.1
Operating income	96.2	45.9	152.1	97.6	247.3	232.7
Other income (loss), net	15.5	7.0	208.5	13.3	22.7	204.5
Gain on sale of business					5.5
Equity in earnings of unconsolidated affiliates	3.9	10.2	23.1	16.9	27.2	45.4
Earnings from continuing operations before interest, income taxes and non-controlling interest	115.6	63.1	383.7	127.8	302.7	482.6
Interest expense	(6.9)	(6.5)	(12.8)	(12.6)	(23.5)	(23.8)
Operating Segments
Summary of financial information of segments [Line Items]
Operating revenues	629.4	373.9	1,009.2	735.2	1,474.4	1,405.0
Operating Segments | Domestic Financial Services
Summary of financial information of segments [Line Items]
Total assets	2,376.4		2,376.4		2,234.9
Operating revenues	297.1	238.8	536.5	471.7	937.7	936.8
Out-of-pocket reimbursements	24.9	14.6	48.8	31.3	73.0	60.7
Total revenues	336.9	268.4	614.8	531.5	1,068.8	1,043.8
Costs and expenses	286.9	224.7	507.7	435.0	829.0	792.3
Depreciation and amortization	21.8	19.4	40.7	36.9	77.3	67.7
Operating income	28.2	24.3	66.4	59.6	162.5	183.8
Other income (loss), net	16.7	4.1	220.4	7.8	13.9	207.2
Equity in earnings of unconsolidated affiliates	2.2	3.8	8.4	8.9	14.3	23.8
Earnings from continuing operations before interest, income taxes and non-controlling interest	47.1	32.2	295.2	76.3	190.7	414.8
Operating Segments | International Financial Services
Summary of financial information of segments [Line Items]
Total assets	742.5		742.5		430.0
Operating revenues	231.0	31.1	263.7	55.3	110.5	91.8
Out-of-pocket reimbursements	0.1	0.3	0.3	0.6	1.2	1.7
Total revenues	231.2	31.5	264.2	56.1	112.1	95.1
Costs and expenses	170.5	26.3	203.1	49.3	98.2	86.1
Depreciation and amortization	10.6	0.9	11.6	1.2	3.1	4.8
Operating income	50.1	4.3	49.5	5.6	10.8	4.2
Other income (loss), net	(1.1)	2.9	(11.9)	5.5	8.7	(2.6)
Gain on sale of business					5.5
Equity in earnings of unconsolidated affiliates	1.5	6.4	14.4	7.9	12.4	21.3
Earnings from continuing operations before interest, income taxes and non-controlling interest	50.5	13.6	52.0	19.0	37.4	22.9
Operating Segments | Healthcare Services
Summary of financial information of segments [Line Items]
Total assets	488.9		488.9		552.2
Operating revenues	101.3	104.0	209.0	208.2	426.2	376.4
Out-of-pocket reimbursements	1.8	2.0	3.6	4.5	8.5	8.2
Total revenues	103.1	106.0	212.6	212.7	434.7	384.6
Costs and expenses	82.8	84.8	170.7	172.1	345.1	321.3
Depreciation and amortization	2.4	3.9	5.7	8.2	15.6	18.6
Operating income	17.9	17.3	36.2	32.4	74.0	44.7
Other income (loss), net	(0.1)	0.0	0.0	0.0	0.1	(0.1)
Gain on sale of business					0.0
Equity in earnings of unconsolidated affiliates	0.2	0.0	0.3	0.1	0.5	0.3
Earnings from continuing operations before interest, income taxes and non-controlling interest	18.0	17.3	36.5	32.5	74.6	44.9
Operating Segments | Financial Services [Member]
Summary of financial information of segments [Line Items]
Gain on sale of business					0.0
Intersegment Eliminations
Summary of financial information of segments [Line Items]
Total assets	(642.9)		(642.9)		(517.9)
Operating revenues	(15.0)	(15.1)	(29.7)	(28.7)	(58.5)	(47.9)
Out-of-pocket reimbursements	0.0	(0.3)	(0.2)	(0.4)	(0.4)	(1.6)
Total revenues	(15.0)	(15.4)	(29.9)	(29.1)	(58.9)	(49.5)
Costs and expenses	(15.0)	(15.4)	(29.9)	(29.1)	(58.9)	(49.5)
Depreciation and amortization	0.0	0.0	0.0	0.0	0.0	0.0
Operating income	0.0	0.0	0.0	0.0	0.0	0.0
Other income (loss), net	0.0	0.0	0.0	0.0	0.0	0.0
Gain on sale of business					0.0
Equity in earnings of unconsolidated affiliates	0.0	0.0	0.0	0.0	0.0	0.0
Earnings from continuing operations before interest, income taxes and non-controlling interest	0.0	0.0	0.0	0.0	0.0	0.0
Intersegment Eliminations | Domestic Financial Services
Summary of financial information of segments [Line Items]
Operating revenues	14.9	15.0	29.5	28.5	58.1	46.3
Intersegment Eliminations | International Financial Services
Summary of financial information of segments [Line Items]
Operating revenues	0.1	0.1	0.2	0.2	0.4	1.6
Intersegment Eliminations | Healthcare Services
Summary of financial information of segments [Line Items]
Operating revenues	0.0	$ 0.0	0.0	$ 0.0	0.0	$ 0.0
Discontinued Operations, Held-for-sale | Customer Communications
Summary of financial information of segments [Line Items]
Assets held for sale	$ 0.0		$ 0.0		$ 72.6