Earnings Per Share - Antidilutive Securities Excluded from Computation of EPS Table (Details) - shares shares in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Common stock equivalent of our preferred stock outstanding prior to exchange
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Shares of common stock that were excluded from the calculation of diluted EPS (in shares)	1	0	1	0
Common stock equivalent of our convertible senior notes outstanding
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Shares of common stock that were excluded from the calculation of diluted EPS (in shares)	124	146	124	146
Participating securities
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Shares of common stock that were excluded from the calculation of diluted EPS (in shares)	0	2	0	1
Common stock equivalent of our preferred stock outstanding
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Shares of common stock that were excluded from the calculation of diluted EPS (in shares)	58	60	58	60