Debt Debt Obligation Maturities (Details) - USD ($) $ in Millions		Dec. 31, 2016	Dec. 31, 2015
Debt Maturities [Abstract]
Debt maturities - 2017		$ 735
Debt maturities - 2018		739
Debt maturities - 2019		836
Debt maturities - 2020		570
Debt maturities - 2021		918
Debt maturities - Thereafter		18,246
Total Debt	[1]	22,044	$ 21,737
Total Debt excluding capital leases	[2],[3]	21,509
Total Debt excluding capital leases, Fair Value	[3]	23,618	$ 21,996
Outstanding variable rate debt		$ 0
Weighted Average Interest Rate on Debt and Capital Lease Obligations [Abstract]
Weighted Average Interest Rate On Debt And Capital Lease Obligations - 2017		5.60%
Weighted Average Interest Rate On Debt And Capital Lease Obligations - 2018		5.70%
Weighted Average Interest Rate On Debt And Capital Lease Obligations - 2019		4.80%
Weighted Average Interest Rate On Debt And Capital Lease Obligations - 2020		5.70%
Weighted Average Interest Rate On Debt And Capital Lease Obligations - 2021		4.30%
Weighted Average Interest Rate On Debt And Capital Lease Obligations - Thereafter		4.80%
Total Debt, Weighted Average Interest Rate		4.80%
Junior Subordinated Debt [Member]
Debt Instrument [Line Items]
Subordinated notes related to financial covenants		$ 500

[1] Amounts represent debt outstanding and weighted average effective interest rates for 2016 and 2015, respectively. Maturities are as of December 31, 2016.

[2] Amount also excludes unamortized fair value adjustment under acquisition method accounting related to capital leases.

[3] Amount also excludes unamortized gains on interest rate swaps.