Derivative and Hedging Activities - Components of Interest Income and Interest Expense Table (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Interest expense on senior notes	$ 135	$ 141	$ 407	$ 446
Interest expense on term loan	34	14	98	14
Amortization of loan discount, issuance costs and other	13	9	28	27
Amortization of premium associated with troubled debt restructuring	(29)	(41)	(112)	(124)
Interest expense on revolving credit facility	11	10	28	27
Gains on terminated fair value hedges	(1)	(1)	(1)	(2)
Losses on undesignated interest rate derivatives	0	0	1	0
Capitalized interest	(49)	(59)	(147)	(191)
Total interest expense	$ 114	$ 73	$ 302	$ 197