Fair Value Of Financial Instruments (Narrative) (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Percentage of level 3 assets at fair value in total assets measured at fair value value	27.00%		27.00%		21.00%
Percentage of level 3 liabilities at fair value in total liabilities measured at fair value	41.00%		41.00%		37.00%
Transfers into or out of Level 1	$ 0	$ 0	$ 0	$ 0