Insurance Premiums (Undiscounted Future Amount Of Premiums Expected To Be Collected And Period Which Those Collections Are Expected To Occur) (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012
Three months ended, March 31, 2013, Expected Collection of Premiums	$ 30
Three months ended, June 30, 2013, Expected Collection of Premiums	43
Three months ended, September 30, 2013, Expected Collection of Premiums	30
Three months ended, December 31, 2013, Expected Collection of Premiums	36
Twelve months ended, December 31, 2014, Expected Collection of Premiums	125
Twelve months ended, December 31, 2015, Expected Collection of Premiums	117
Twelve months ended, December 31, 2016, Expected Collection of Premiums	109
Twelve months ended, December 31, 2017, Expected Collection of Premiums	99
Five years ended, December 31, 2022, Expected Collection of Premiums	378
Five years ended, December 31, 2027, Expected Collection of Premiums	264
Five years ended, December 31, 2032 and thereafter, Expected Collection of Premiums	303
Total, Expected Collection of Premiums	$ 1,534