Equity (Narrative) (Detail) - USD ($) $ in Millions	3 Months Ended
	Jun. 30, 2015	Mar. 31, 2015
Fees and commissions		$ 1
Equity Contract [Member]
Equity Distribution Agreement, shares issued		1,400,000
Equity distribution agreement amount	$ 500
Stock Issued During Period Value Under Equity Distribution Agreement		$ 74
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	4,300,000
Stock Issued During Period Value Stock Options Exercised	$ 178