Mergers and Acquisitions - Schedule of Acquired Loans Accounted for at Fair value (Detail) (USD $) In Thousands, unless otherwise specified	Jan. 31, 2014
Business Acquisition [Line Items]
Contractually required principal and interest at acquisition	$ 405,109
Expected cash flows at acquisition	166,874
Basis in acquired loans at acquisition - estimated fair value	157,759
Virginia Commerce Bancorp, Inc. [Member]
Business Acquisition [Line Items]
Contractually required principal and interest at acquisition	2,683,966
Contractual cash flows not expected to be collected	(396,983)
Expected cash flows at acquisition	2,286,983
Interest component of expected cash flows	(274,462)
Basis in acquired loans at acquisition - estimated fair value	$ 2,012,521