Leases - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014 Contract	Mar. 31, 2014	Dec. 31, 2013
Operating Leased Assets [Line Items]
Other current liabilities (liabilities held-for-sale)	0	$ 46	$ 46
Present value of net minimum lease payments associated with capital leases			51
Lower Limit
Operating Leased Assets [Line Items]
Number of lease renewal options	1
Renewal option period	5 years
Upper Limit
Operating Leased Assets [Line Items]
Leases, initial terms	20 years
Renewal option period	10 years
Primary Obligations Operating Leases
Operating Leased Assets [Line Items]
Obligations of consolidated subsidiaries	1,077
Consolidated Subsidiaries Non Recourse to Parent | Primary Obligations Operating Leases
Operating Leased Assets [Line Items]
Obligations of consolidated subsidiaries	233