Shareholders' Equity - RSU Awards and SSAR Awards (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
RSUs
Awards Outstanding
Balance at the beginning of the period (in shares)	1.3	1.6	1.2
Granted (in shares)	0.3	0.2	0.6
Vested (in shares)	(0.4)	(0.3)	(0.2)
Forfeited (in shares)	(0.1)	(0.2)	(0.1)
Balance at the end of the period (in shares)	1.2	1.3	1.6	1.2
Weighted Average Grant date Fair Value Price
Balance at the beginning of the period (in dollars per share)	$ 37.17	$ 41.01	$ 43.28
Granted (in dollars per share)	29.69	22.02	37.74
Vested (in dollars per share)	37.34	46.31	43.06
Forfeited (in dollars per share)	39.86	41.17	42.43
Balance at the end of the period (in dollars per share)	$ 32.50	$ 37.17	$ 41.01	$ 43.28
Aggregate Intrinsic Value	$ 53.2	$ 28.3	$ 43.9	$ 55.7
Weighted Average Remaining Vesting Term	10 months 24 days	1 year	1 year 4 months 24 days	1 year 7 months 6 days
Aggregate intrinsic value of awards issued	$ 10.4	$ 5.8	$ 7.7
SSAR Awards
Weighted Average Grant date Fair Value Price
Aggregate Intrinsic Value	$ 31.3	$ 0.0	$ 0.0	$ 0.3
Weighted Average Remaining Vesting Term	3 years 4 months 24 days	4 years	3 years	2 years 4 months 24 days
SSAR Awards
Balance at the beginning of the period (in shares)	1.5	0.7	0.3
Granted (in shares)	0.7	1.2	0.4
Forfeited (in shares)	0.0	(0.4)	0.0
Exercised (in shares)	0.0	0.0	0.0
Balance at the end of the period (in shares)	2.2	1.5	0.7	0.3
Weighted Average Exercise Price
Balance at the beginning of the period (in dollars per share)	$ 29.75	$ 40.27	$ 44.97
Granted (in dollars per share)	29.68	27.08	36.31
Exercised (in dollars per share)	0	0	0
Forfeited (in dollars per share)	0	38.53	0
Balance at the end of the period (in dollars per share)	$ 29.72	$ 29.75	$ 40.27	$ 44.97
SSAR Awards Exercisable
SSAR Awards (in shares)	0.1	0.0	0.2	0.2
Weighted Average Exercise Price (in dollars per share)	$ 50.12	$ 57.48	$ 42.76	$ 42.15
Aggregate Intrinsic Value	$ 0.0	$ 0.0	$ 0.0	$ 0.7
Weighted Average Remaining Contractual Life	1 year 1 month 6 days	1 year 2 months 12 days	4 months 24 days	1 year 3 months 18 days
Aggregate intrinsic value of SSAR Awards exercised	$ 0.0	$ 0.0
Weighted average fair value of SSAR Awards (in dollars per share)	$ 9.15	$ 6.56	$ 8.82
Expected term	4 years 6 months	4 years 6 months	4 years 3 months 18 days
Volatility	36.10%	30.80%	28.60%
Dividend yields	0.90%	1.00%	0.70%
Risk-free interest rates	2.40%	2.60%	1.80%