Capital Ratios and Other Regulatory Matters - Actual Capital Amounts and Ratios (Parenthetical) (Detail)	3 Months Ended
	Mar. 31, 2015
Regulated Operations [Abstract]
Capital conservation buffer ratio	0.625%
Capital conversion description	This capital conservation buffer will increase in subsequent years by 0.625% annually until it is fully phased in on January 1, 2019 at 2.50%.