Equity Investments - Summary of Equity Method Investments (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Equity Method Investments and Joint Ventures [Abstract]
Revenues	$ 962.8	$ 901.1	$ 949.5
Revenues less cost of revenue	352.5	398.4	506.4
Net income	83.1	90.4	111.2
Current assets	879.6	870.5
Noncurrent assets	1,062.8	1,500.9
Current liabilities	648.8	621.9
Noncurrent liabilities	$ 41.9	$ 156.9