Equity (Narrative) (Detail) (USD $) In Millions, except Share data, unless otherwise specified	3 Months Ended	9 Months Ended
	Sep. 30, 2014	Sep. 30, 2014	Feb. 12, 2014
Equity Contract [Member]
Equity Distribution Agreement, shares issued	2	11
Equity distribution agreement amount			$ 500
Fees and commissions	1	4
Stock Issued During Period Value Under Equity Distribution Agreement	67	496
401K Plan, DRSPP, and Shared Based Compensation Plans [Member]
Stock issued during period for stock options exercised and under 401(K) plan and DRSPP, shares		7
Stock Issued During Period Value Stock Options Exercised		$ 247