Unconsolidated Affiliates - Related Party Transactions (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Feb. 27, 2017
Amounts and transactions with related party unconsolidated affiliates
Operating revenues from related parties	$ 55.4	$ 138.5	$ 134.9
Amounts paid to related parties (1)	42.7	36.8	27.3
Distributions received from related parties	18.6	3.5	15.3
Outstanding advances/loans to related parties	6.1	31.4
Trade accounts receivable from related parties	6.7	19.7
Total amounts receivable from related parties	12.8	51.1
Amounts payable to related parties	0.6	$ 3.4
Boston Financial Data Services, Inc.
Amounts and transactions with related party unconsolidated affiliates
Outstanding advances/loans to related parties			$ 1.5
International Financial Data Services U.K.
Amounts and transactions with related party unconsolidated affiliates
Outstanding advances/loans to related parties	28.0			$ 12.5
Broadway Square Partners, LLP
Amounts and transactions with related party unconsolidated affiliates
Outstanding advances/loans to related parties	$ 1.2