Business Segments, Geographic Information, and Major Customers - Geographic Summary (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
Revenue:
Revenue	$ 7,792.1	$ 7,399.8	$ 6,633.0	$ 5,190.8	$ 6,733.6	$ 7,810.7	$ 8,496.4	$ 7,340.7	$ 27,015.8	$ 30,381.4	$ 43,391.8
Income from operations:
Income from operations									188.9	245.7	276.7
Non-current assets:
Non-current assets	1,576.1				1,279.3				1,576.1	1,279.3
Total assets:
Total assets	5,412.6				4,525.3				5,412.6	4,525.3
Revenue	7,792.1	$ 7,399.8	$ 6,633.0	$ 5,190.8	6,733.6	$ 7,810.7	$ 8,496.4	$ 7,340.7	27,015.8	30,381.4	43,391.8
United States
Revenue:
Revenue									14,368.8	15,496.3	21,519.6
Income from operations:
Income from operations									(26.1)	19.2	51.8
Non-current assets:
Non-current assets	799.2				639.9				799.2	639.9
Total assets:
Total assets	2,462.0				1,890.5				2,462.0	1,890.5
Revenue									14,368.8	15,496.3	21,519.6
EMEA
Revenue:
Revenue									6,018.6	6,382.2	8,613.1
Income from operations:
Income from operations									155.3	153.8	123.7
Non-current assets:
Non-current assets	587.4				604.6				587.4	604.6
Total assets:
Total assets	1,805.6				1,719.5				1,805.6	1,719.5
Revenue									6,018.6	6,382.2	8,613.1
Asia/Pacific
Revenue:
Revenue									4,271.1	5,863.4	9,844.7
Income from operations:
Income from operations									38.3	54.4	76.2
Non-current assets:
Non-current assets	17.2				5.3				17.2	5.3
Total assets:
Total assets	661.2				614.9				661.2	614.9
Revenue									4,271.1	5,863.4	9,844.7
Americas, excluding United States
Revenue:
Revenue									2,357.2	2,639.5	3,414.4
Income from operations:
Income from operations									21.3	18.2	24.9
Non-current assets:
Non-current assets	172.4				29.5				172.4	29.5
Total assets:
Total assets	$ 483.9				$ 300.2				483.9	300.2
Revenue									2,357.2	2,639.5	3,414.4
U.K.
Revenue:
Revenue									4,100.0	4,700.0	6,200.0
Total assets:
Revenue									4,100.0	4,700.0	6,200.0
Singapore
Revenue:
Revenue									4,200.0	5,800.0	9,700.0
Total assets:
Revenue									$ 4,200.0	$ 5,800.0	$ 9,700.0