Commitments and Contingencies (Tables)

12 Months Ended

Dec. 31, 2017

Commitments And Contingencies [Abstract]

Future Minimum Rental Commitments for All Long-Term Noncancelable Operating Leases

($ in millions)	Operating Leases
Year ending December 31:
2018	$	80
2019		25
2020		29
2021		26
2022		23
Thereafter		388
Total minimum lease payments	$	571

Future Payments for Obligations under Noncancelable Long Distance Contracts and Service Agreements

($ in millions)	Amount
Year ending December 31:
2018	$	37
2019		40
2020		31
2021		7
2022		2
Thereafter		9
Total	$	126

Outstanding Performance Letters of Credit

($ in millions)	Amount
CNA Financial Corporation (CNA)	$	49
AIG Insurance		114
Zurich		28
All other		1
Total	$	192