Insurance Premiums (Undiscounted Future Amount Of Premiums Expected To Be Collected And Period Which Those Collections Are Expected To Occur) (Detail) $ in Millions	Dec. 31, 2018 USD ($)
Insurance Premiums [Abstract]
Three months ending, March 31, 2019, Expected Collection of Premiums	$ 4
Three months ending, June 30, 2019, Expected Collection of Premiums	12
Three months ending, September 30, 2019, Expected Collection of Premiums	6
Three months ending, December 31, 2019, Expected Collection of Premiums	12
Twelve months ending, December 31, 2020, Expected Collection of Premiums	32
Twelve months ending, December 31, 2021, Expected Collection of Premiums	30
Twelve months ending, December 31, 2022, Expected Collection of Premiums	26
Twelve months ending, December 31, 2023, Expected Collection of Premiums	23
Five years ending, December 31, 2028, Expected Collection of Premiums	86
Five years ending, December 31, 2033, Expected Collection of Premiums	54
Five years ending, December 31, 2038 and thereafter, Expected Collection of Premiums	72
Total, Expected Collection of Premiums	$ 357