Employee Benefit Plans - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plan Disclosure [Line Items]
Contributions	$ 36	$ 33	$ 32
Amortized from accumulated other comprehensive income into net periodic benefit cost	7
Defined Benefit Plan, Plan with Benefit Obligation in Excess of Plan Assets, Benefit Obligation	453	720
Defined Benefit Plan, Plan with Benefit Obligation in Excess of Plan Assets, Fair Value of Plan Assets	264	523
Defined Benefit Plan, Accumulated Benefit Obligation	769	712
Estimated future benefit payments, 2014	26
Estimated future benefit payments, 2015	28
Estimated future benefit payments, 2016	28
Estimated future benefit payments, 2017	29
Estimated future benefit payments, 2018	31
Estimated future benefit payments, 2019 to 2023	170
Contribution to multiemployer plans	$ 9	$ 9	$ 9