Securities - Available for Sale Securities (Unrealized Loss Position) (Parenthetical) (Detail) (Maximum [Member], USD $)	3 Months Ended		12 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014
Other Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross unrealized losses, available for sale securities	$ 1,000,000	$ 1,000,000	$ 1,000,000
Gross unrealized losses, held-to-maturity securities	1,000,000	1,000,000
Other Mortgage-Backed Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Gross unrealized losses, available for sale securities	$ 1,000,000