Summary Quarterly Financial Information Summary of Quarterly Financial Information (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended									9 Months Ended	12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Apr. 01, 2017	Dec. 31, 2017	Dec. 31, 2019	Dec. 31, 2018
Selected Quarterly Financial Information [Abstract]
Revenues	$ 1,117.4	$ 1,106.4	$ 1,149.0	$ 1,250.6	$ 1,397.1	$ 1,412.6	$ 1,309.4	$ 1,462.7	$ 1,326.2	$ 4,252.6	$ 4,623.4	$ 5,581.8
Operating profit (loss)	(165.5)	(36.8)	79.5	184.5	126.8	130.3	165.3	239.2	212.5	663.8	61.7	661.6
Income (loss) from continuing operations, net of income taxes	(290.2)	(74.3)	42.9	133.3	233.5	83.9	120.0	208.3	(195.5)	713.1	(188.3)	645.7
Net income (loss)	(276.4)	(78.1)	39.5	129.9	260.6	79.8	116.4	207.0	(211.7)	693.3	(185.1)	663.8
Net income (loss) attributable to common stockholders	$ (289.8)	$ (82.8)	$ 37.1	$ 124.2	$ 252.6	$ 71.5	$ 113.7	$ 106.6	$ (216.5)	$ 498.6	$ (211.3)	$ 544.4
Basic EPS — continuing operations (1)	$ (3.12)	$ (0.77)	$ 0.38	$ 1.18	$ 1.99	$ 0.64	$ 0.94	$ 0.84	$ (10.93)	$ 3.85	$ (2.07)	$ 4.35
Diluted EPS — continuing operations (1)	$ (3.12)	$ (0.77)	$ 0.37	$ 1.15	$ 1.97	$ 0.63	$ 0.93	$ 0.83	$ (10.93)	$ 3.81	$ (2.07)	$ 4.28
Weighted average shares used in calculating basic EPS	97.3	102.2	107.0	108.5	113.1	118.6	124.5	120.9	18.3	101.1	103.7	119.3
Weighted average shares used in calculating diluted EPS	97.3	102.2	108.1	110.5	114.7	120.3	126.0	123.2		33.5		2.1