Commitments - Other Commitments (Detail) (USD $) In Billions, unless otherwise specified	12 Months Ended
	Dec. 31, 2013
Unrecorded Unconditional Purchase Obligation [Line Items]
Aggregate future payments	$ 11.5
Aggregate future payments expected to be paid in 2014	2.3
Aggregate future payments expected to be paid in 2015	1.8
Aggregate future payments expected to be paid in 2016	1.4
Aggregate future payments expected to be paid in 2017	1.2
Aggregate future payments expected to be paid in 2018	1.1
Aggregate future payments expected to be paid thereafter	$ 3.7
Maximum [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Other commitments, expiration date	Dec. 31, 2030