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, 2016 USD ($)
Insurance Premiums [Abstract]
Three months ending, March 31, 2017, Expected Collection of Premiums	$ 7
Three months ending, June 30, 2017, Expected Collection of Premiums	16
Three months ending, September 30, 2017, Expected Collection of Premiums	8
Three months ending, December 31, 2017, Expected Collection of Premiums	15
Twelve months ending, December 31, 2018, Expected Collection of Premiums	41
Twelve months ending, December 31, 2019, Expected Collection of Premiums	37
Twelve months ending, December 31, 2020, Expected Collection of Premiums	34
Twelve months ending, December 31, 2021, Expected Collection of Premiums	31
Five years ending, December 31, 2026, Expected Collection of Premiums	126
Five years ending, December 31, 2031, Expected Collection of Premiums	82
Five years ending, December 31, 2036 and thereafter, Expected Collection of Premiums	109
Total, Expected Collection of Premiums	$ 506