Cash and Cash Equivalents (Detail) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Cash and Cash Equivalents [Abstract]
Cash and due from banks	$ 2,352,469	$ 1,372,743
Securities purchased under agreements to resell	163,719	125,391
Other short-term investment securities	5,131	5,123
Total cash and cash equivalents	$ 2,521,319	$ 1,503,257