Long-term Debt (Details) £ in Millions, $ in Millions, ¥ in Billions	3 Months Ended	6 Months Ended
Jun. 30, 2019 USD ($)	Jun. 30, 2019 USD ($)	Jun. 30, 2019 GBP (£)	Jun. 30, 2019 JPY (¥)
Debt Instrument [Line Items]
Redemption Premium	$ 40	$ 40
Debt Issuance Costs, Gross	$ 9	9
Senior Debt GBP 400 Million June 2020 [Member]
Debt Instrument [Line Items]
Repayments of Debt		$ 509	£ 400
Debt Instrument, Interest Rate, Stated Percentage	5.25%	5.25%		5.25%
Debt Instrument, Maturity Date		Jun. 29, 2020	Jun. 29, 2020
Senior Debt $368 Million February 2021 [Member]
Debt Instrument [Line Items]
Repayments of Debt		$ 368
Debt Instrument, Interest Rate, Stated Percentage	4.75%	4.75%		4.75%
Debt Instrument, Maturity Date		Feb. 08, 2021	Feb. 08, 2021
Senior Debt Yen 25.2 Billion May 2026 [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 230	$ 230		¥ 25.2
Debt Instrument, Interest Rate, Stated Percentage	0.495%	0.495%		0.495%
Debt Instrument, Maturity Date		May 22, 2026	May 22, 2026
Senior Debt Yen 64.9 Billion May 2029 [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 591	$ 591		¥ 64.9
Debt Instrument, Interest Rate, Stated Percentage	0.769%	0.769%		0.769%
Debt Instrument, Maturity Date		May 23, 2029	May 23, 2029
Senior Debt Yen 10.7 Billion May 2031 [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 98	$ 98		¥ 10.7
Debt Instrument, Interest Rate, Stated Percentage	0.898%	0.898%		0.898%
Debt Instrument, Maturity Date		May 23, 2031	May 23, 2031
Senior Debt Yen 26.5 Billion May 2034 [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 241	$ 241		¥ 26.5
Debt Instrument, Interest Rate, Stated Percentage	1.189%	1.189%		1.189%
Debt Instrument, Maturity Date		May 23, 2034	May 23, 2034
Senior Debt Yen 24.4 Billion May 2039 [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 222	$ 222		¥ 24.4
Debt Instrument, Interest Rate, Stated Percentage	1.385%	1.385%		1.385%
Debt Instrument, Maturity Date		May 23, 2039	May 23, 2039

Face (par) amount of debt instrument at time of issuance.

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Contractual interest rate for funds borrowed, under the debt agreement.

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