Acquisition (Summary of Loans Acquired) (Detail) (Tower [Member], USD $) In Thousands, unless otherwise specified	Feb. 17, 2012
Business Acquisition [Line Items]
Contractually required principal and interest at acquisition	$ 2,724,960
Contractual cash flows not expected to be collected	(263,054)
Expected cash flows at acquisition	2,461,906
Interest component of expected cash flows	(486,418)
Basis in acquired loans at acquisition - estimated fair value	1,975,488
Purchased Credit Impaired Loans [Member]
Business Acquisition [Line Items]
Contractually required principal and interest at acquisition	348,889
Contractual cash flows not expected to be collected	(127,318)
Expected cash flows at acquisition	221,571
Interest component of expected cash flows	(54,418)
Basis in acquired loans at acquisition - estimated fair value	167,153
Purchased Non Impaired Loans [Member]
Business Acquisition [Line Items]
Contractually required principal and interest at acquisition	2,376,071
Contractual cash flows not expected to be collected	(135,736)
Expected cash flows at acquisition	2,240,335
Interest component of expected cash flows	(432,000)
Basis in acquired loans at acquisition - estimated fair value	$ 1,808,335