Organization, Basis of Presentation and Summary of Significant Accounting Policies (Details - Adoption of New Accounting Standards) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2018	Sep. 30, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Losses on early extinguishment of debt		$ (58)	$ (4)	$ (58)	$ 0
Cumulative effect of accounting change				3
Transfer of held-to-maturity securities to available-for-sale securities			4,672	0	0
Other comprehensive income, transfers from held-to-maturity to available-for-sale securities, before tax			7	0	$ 0
Operating Lease, Right-of-Use Asset			193
Operating Lease, Liability			211
Retained Earnings (Accumulated Deficit)
Cumulative effect of accounting change				3
Accounting Standards Update 2016-15 [Member]
Losses on early extinguishment of debt				$ 49
Accounting Standards Update 2017-12 [Member]
Transfer of held-to-maturity securities to available-for-sale securities			4,700
Other comprehensive income, transfers from held-to-maturity to available-for-sale securities, before tax			7
Accounting Standards Update 2017-12 [Member] | Retained Earnings (Accumulated Deficit)
Cumulative effect of accounting change			7
Accounting Standards Update 2018-02 [Member] | Retained Earnings (Accumulated Deficit)
Cumulative effect of accounting change	$ 14		$ 14