Related Party Transactions (Schedule of Dividends Paid to Manager) (Details) - USD ($) $ / shares in Units, $ in Millions	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016
Related Party Transactions [Abstract]
Cash dividend declared per share (in dollars per share)	$ 1.00	$ 1.00	$ 1.00	$ 1.00	$ 1.00	$ 1.00	$ 1.00	$ 1.00	$ 1.44	$ 1.42	$ 1.38	$ 1.32	$ 1.31
Cash Paid to Manager		$ 13	$ 13	$ 13	$ 13	$ 12	$ 11	$ 6	$ 8	$ 7	$ 7	$ 6	$ 6