Share-based Compensation (Stock Award Activity, Options, SARs & PSARs) (Schedules) (Details) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2019 USD ($) $ / shares shares
Options | Class A
Number of awards
Options outstanding at beginning of period (in shares) | shares	580,254
Options granted (in shares) | shares	61,244
Options exercised (in dollars per share) | shares	(53,240)
Options outstanding at end of period (in shares) | shares	588,258
Options exercisable and end of period (in shares) | shares	447,042
Weighted average exercise or base price
Options outstanding at beginning of period (in dollars per shares) | $ / shares	$ 27.51
Options granted (in dollars per shares) | $ / shares	26.47
Options exercised (in dollars per share) | $ / shares	7.10
Options outstanding at end of period (in dollars per shares) | $ / shares	29.25
Options exercisable at end of period (in dollars per share) | $ / shares	$ 29.40
Weighted average remaining contractual term
Options outstanding at end of period	3 years 8 months 12 days
Options exercisable at end of period	2 years 7 months 6 days
Aggregate intrinsic value
Options outstanding at end of period | $	$ 0.7
Options exercisable at end of period | $	$ 0.7
Options | Class C
Number of awards
Options outstanding at beginning of period (in shares) | shares	2,667,506
Options granted (in shares) | shares	1,364,721
Options expired, cancelled or forfeited (in shares) | shares	(349,474)
Options exercised (in dollars per share) | shares	(176,185)
Options outstanding at end of period (in shares) | shares	3,506,568
Options exercisable and end of period (in shares) | shares	2,820,918
Weighted average exercise or base price
Options outstanding at beginning of period (in dollars per shares) | $ / shares	$ 25.09
Options granted (in dollars per shares) | $ / shares	24.52
Options expired, cancelled or forfeited (in dollars per shares) | $ / shares	24.79
Options exercised (in dollars per share) | $ / shares	6.92
Options outstanding at end of period (in dollars per shares) | $ / shares	25.81
Options exercisable at end of period (in dollars per share) | $ / shares	$ 25.68
Weighted average remaining contractual term
Options outstanding at end of period	3 years
Options exercisable at end of period	2 years 1 month 6 days
Aggregate intrinsic value
Options outstanding at end of period | $	$ 1.7
Options exercisable at end of period | $	$ 1.7
SARs | Class A
Number of awards
Options outstanding at beginning of period (in shares) | shares	15,308,562
Options granted (in shares) | shares	3,350,635
Options expired, cancelled or forfeited (in shares) | shares	(1,520,202)
Options exercised (in dollars per share) | shares	(509,520)
Impact of the sale of the Vodafone Disposal Group (in shares) | shares	(377,858)
Options outstanding at end of period (in shares) | shares	16,251,617
Options exercisable and end of period (in shares) | shares	10,951,161
Weighted average exercise or base price
Options outstanding at beginning of period (in dollars per shares) | $ / shares	$ 32.41
Options granted (in dollars per shares) | $ / shares	24.92
Options expired, cancelled or forfeited (in dollars per shares) | $ / shares	32.62
Options exercised (in dollars per share) | $ / shares	19.91
Impact of the sale of the Vodafone Disposal Group (in dollars per share) | $ / shares	34.89
Options outstanding at end of period (in dollars per shares) | $ / shares	31.18
Options exercisable at end of period (in dollars per share) | $ / shares	$ 32.66
Weighted average remaining contractual term
Options outstanding at end of period	3 years 10 months 24 days
Options exercisable at end of period	2 years 4 months 24 days
Aggregate intrinsic value
Options outstanding at end of period | $	$ 0.0
Options exercisable at end of period | $	$ 0.0
SARs | Class C
Number of awards
Options outstanding at beginning of period (in shares) | shares	34,401,980
Options granted (in shares) | shares	6,701,270
Options expired, cancelled or forfeited (in shares) | shares	(3,042,500)
Options exercised (in dollars per share) | shares	(1,599,608)
Impact of the sale of the Vodafone Disposal Group (in shares) | shares	(778,280)
Options outstanding at end of period (in shares) | shares	35,682,862
Options exercisable and end of period (in shares) | shares	25,082,821
Weighted average exercise or base price
Options outstanding at beginning of period (in dollars per shares) | $ / shares	$ 30.61
Options granted (in dollars per shares) | $ / shares	24.17
Options expired, cancelled or forfeited (in dollars per shares) | $ / shares	31.49
Options exercised (in dollars per share) | $ / shares	19.25
Impact of the sale of the Vodafone Disposal Group (in dollars per share) | $ / shares	33.57
Options outstanding at end of period (in dollars per shares) | $ / shares	29.77
Options exercisable at end of period (in dollars per share) | $ / shares	$ 30.83
Weighted average remaining contractual term
Options outstanding at end of period	3 years 7 months 6 days
Options exercisable at end of period	2 years 1 month 6 days
Aggregate intrinsic value
Options outstanding at end of period | $	$ 0.0
Options exercisable at end of period | $	$ 0.0
PSARs | Class A
Number of awards
Options outstanding at beginning of period (in shares) | shares	0
Options granted (in shares) | shares	4,477,343
Options expired, cancelled or forfeited (in shares) | shares	(405,727)
Options outstanding at end of period (in shares) | shares	4,071,616
Options exercisable and end of period (in shares) | shares	1,118
Weighted average exercise or base price
Options outstanding at beginning of period (in dollars per shares) | $ / shares	$ 0
Options granted (in dollars per shares) | $ / shares	25.97
Options expired, cancelled or forfeited (in dollars per shares) | $ / shares	25.97
Options outstanding at end of period (in dollars per shares) | $ / shares	25.97
Options exercisable at end of period (in dollars per share) | $ / shares	$ 25.97
Weighted average remaining contractual term
Options outstanding at end of period	9 years 2 months 12 days
Options exercisable at end of period	9 months 18 days
Aggregate intrinsic value
Options outstanding at end of period | $	$ 0.0
Options exercisable at end of period | $	$ 0.0
PSARs | Class C
Number of awards
Options outstanding at beginning of period (in shares) | shares	0
Options granted (in shares) | shares	8,954,686
Options expired, cancelled or forfeited (in shares) | shares	(811,454)
Options outstanding at end of period (in shares) | shares	8,143,232
Options exercisable and end of period (in shares) | shares	2,236
Weighted average exercise or base price
Options outstanding at beginning of period (in dollars per shares) | $ / shares	$ 0
Options granted (in dollars per shares) | $ / shares	25.22
Options expired, cancelled or forfeited (in dollars per shares) | $ / shares	25.22
Options outstanding at end of period (in dollars per shares) | $ / shares	25.22
Options exercisable at end of period (in dollars per share) | $ / shares	$ 25.22
Weighted average remaining contractual term
Options outstanding at end of period	9 years 2 months 12 days
Options exercisable at end of period	9 months 18 days
Aggregate intrinsic value
Options outstanding at end of period | $	$ 0.0
Options exercisable at end of period | $	$ 0.0
Options and SARs | Class A | Former Employees
Number of awards
Options outstanding at end of period (in shares) | shares	1,509,447
Options exercisable and end of period (in shares) | shares	1,429,022
Weighted average exercise or base price
Options outstanding at end of period (in dollars per shares) | $ / shares	$ 33.96
Options exercisable at end of period (in dollars per share) | $ / shares	$ 33.95
Weighted average remaining contractual term
Options outstanding at end of period	2 years
Options exercisable at end of period	1 year 9 months 18 days
Aggregate intrinsic value
Options outstanding at end of period | $	$ 0.0
Options exercisable at end of period | $	$ 0.0
Options and SARs | Class C | Former Employees
Number of awards
Options outstanding at end of period (in shares) | shares	3,374,752
Options exercisable and end of period (in shares) | shares	3,213,870
Weighted average exercise or base price
Options outstanding at end of period (in dollars per shares) | $ / shares	$ 32.08
Options exercisable at end of period (in dollars per share) | $ / shares	$ 32.02
Weighted average remaining contractual term
Options outstanding at end of period	1 year 9 months 18 days
Options exercisable at end of period	1 year 8 months 12 days
Aggregate intrinsic value
Options outstanding at end of period | $	$ 0.0
Options exercisable at end of period | $	$ 0.0