Recent Accounting Pronouncements (Narrative) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Jan. 01, 2019
SubsequentEvent [Member]
Operating lease right of use		$ 23
ASU 2016-01 [Member] | Financial Liabilities [Member]
Cumulative effect of prospective application of new accounting principle	$ 162
ASU 2016-01 [Member] | Equity Investments [Member]
Cumulative effect of prospective application of new accounting principle	2
ASU 2018-02 [Member]
Cumulative effect of prospective application of new accounting principle	$ 3