Employee Benefit Plans - Plan's Assets Carried at Fair Value (Detail) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Defined Benefit Plan Disclosure [Line Items]
Total Fair Value Measurements	$ 601	$ 660
Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Fair Value Measurements	186	116
Bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Fair Value Measurements	259	323
Other Contract [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Fair Value Measurements	156	221
Fair Value, Inputs, Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Fair Value Measurements	502	552
Fair Value, Inputs, Level 2 [Member] \| Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Fair Value Measurements	186	116
Fair Value, Inputs, Level 2 [Member] \| Bonds [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Fair Value Measurements	259	323
Fair Value, Inputs, Level 2 [Member] \| Other Contract [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Fair Value Measurements	57	113
Fair Value, Inputs, Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Fair Value Measurements	99	108	$ 107
Fair Value, Inputs, Level 3 [Member] \| Other Contract [Member]
Defined Benefit Plan Disclosure [Line Items]
Total Fair Value Measurements	$ 99	$ 108