Shareholders' Equity - RSU Awards and SSAR Awards (Details) - USD ($) $ / shares in Units, shares in Millions	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
SSAR Awards Exercisable
Aggregate intrinsic value of SSAR Awards exercised	$ 0	$ 0	$ 0
RSUs
Awards Outstanding
Balance at the beginning of the period (in shares)	1.2	1.3	1.6
Granted (in shares)	1.2	0.3	0.2
Vested (in shares)	(0.4)	(0.4)	(0.3)
Forfeited (in shares)	(0.2)	(0.1)	(0.2)
Balance at the end of the period (in shares)	1.8	1.2	1.3	1.6
Weighted Average Grant date Fair Value Price
Balance at the beginning of the period (in dollars per share)	$ 32.50	$ 37.17	$ 41.01
Granted (in dollars per share)	23.30	29.69	22.02
Vested (in dollars per share)	36.12	37.34	46.31
Forfeited (in dollars per share)	32.56	39.86	41.17
Balance at the end of the period (in dollars per share)	$ 25.17	$ 32.50	$ 37.17	$ 41.01
Aggregate Intrinsic Value	$ 57,100,000	$ 53,200,000	$ 28,300,000	$ 43,900,000
Weighted Average Remaining Vesting Term (in Years)	1 year 3 months 18 days	10 months 24 days	1 year	1 year 4 months 24 days
Aggregate intrinsic value of awards issued	$ 10,800,000	$ 10,400,000	$ 5,800,000
SSAR Awards
Weighted Average Grant date Fair Value Price
Aggregate Intrinsic Value	$ 7,300,000	$ 31,300,000	$ 0	$ 0
Weighted Average Remaining Vesting Term (in Years)	2 years 6 months	3 years 4 months 24 days	4 years	3 years
SSAR Awards
Balance at the beginning of the period (in shares)	2.2	1.5	0.7
Granted (in shares)	0.1	0.7	1.2
Exercised (in shares)	0.0	0.0	0.0
Forfeited (in shares)	0.0	0.0	(0.4)
Balance at the end of the period (in shares)	2.3	2.2	1.5	0.7
Weighted Average Exercise Price
Balance at the beginning of the period (in dollars per share)	$ 29.72	$ 29.75	$ 40.27
Granted (in dollars per share)	23.39	29.68	27.08
Exercised (in dollars per share)	0	0	0
Forfeited (in dollars per share)	57.48	0	38.53
Balance at the end of the period (in dollars per share)	$ 29.08	$ 29.72	$ 29.75	$ 40.27
SSAR Awards Exercisable
SSAR Awards (in shares)	0.2	0.1	0.0	0.2
Weighted Average Exercise Price (in dollars per share)	$ 41.85	$ 50.12	$ 57.48	$ 42.76
Aggregate Intrinsic Value	$ 0	$ 0	$ 0	$ 0
Weighted Average Remaining Contractual Life (in Years)	9 months 18 days	1 year 1 month 6 days	1 year 2 months 12 days	4 months 24 days
Weighted average fair value of SSAR Awards (in dollars per share)	$ 6.88	$ 9.15	$ 6.56
Expected term	4 years 6 months	4 years 6 months	4 years 6 months
Volatility	38.60%	36.10%	30.80%
Dividend yields	1.20%	0.90%	1.00%
Risk-free interest rates	0.70%	2.40%	2.60%

The aggregate intrinsic value of outstanding awards of equity-based plans excluding option plans for which the employer is contingently obligated to issue equity instruments or transfer assets to an employee who has not yet satisfied service or performance criteria necessary to gain title to proceeds from the sale of the award or underlying shares or units, as calculated by applying the disclosed pricing methodology.

No definition available.