Borrowed Funds - Schedule of Long-Term Borrowings (Detail) - USD ($) $ in Thousands		Dec. 31, 2015	Dec. 31, 2014
Debt Instrument [Line Items]
Total long-term borrowings		$ 1,810,728	$ 2,525,044
Deferred issuance costs		2,200	1,400
Long-term borrowings [Member]
Debt Instrument [Line Items]
FHLB advances		1,272,591	1,832,166
Securities sold under agreements to repurchase		307,500	462,500
Subordinated debt, net	[1]	230,573	229,944
Other		64	434
Total long-term borrowings		$ 1,810,728	$ 2,525,044

[1] Subordinated debt is presented net of debt issuance costs totaling $2.2 million and $1.4 million at December 31, 2015 and 2014, respectively.