Other short-term borrowings (Detail) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Short-term Debt [Line Items]
Advances with the FHLB paying interest at maturity	$ 0	$ 400,000
Others	1,200	1,200
Total other short-term borrowings	$ 1,200	$ 401,200