Cash and Cash Equivalents (Detail) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016	Mar. 31, 2016	Dec. 31, 2015
Cash and Cash Equivalents [Abstract]
Cash and due from banks	$ 3,612,954	$ 2,476,588
Securities purchased under agreements to resell	178,037	64,028
Other short-term investment securities	4,688	5,134
Total cash and cash equivalents	$ 3,795,679	$ 2,545,750	$ 1,868,512	$ 1,503,257