Schedule of the Remaining Contractual Maturity by Collateral Type of Securities Sold Under Agreements To Repurchase (Details) - USD ($)	Sep. 30, 2015	Dec. 31, 2014	Sep. 30, 2014
Transfer Of Certain Financial Assets Accounted For As Secured Borrowings [Line Items]
Securities sold under agreements to repurchase	$ 332,329,000	$ 562,214,000	$ 479,384,000
U.S. treasuries
Transfer Of Certain Financial Assets Accounted For As Secured Borrowings [Line Items]
Securities sold under agreements to repurchase	23,812,000
Government agency issued CMO
Transfer Of Certain Financial Assets Accounted For As Secured Borrowings [Line Items]
Securities sold under agreements to repurchase	308,517,000
Overnight and Continuous
Transfer Of Certain Financial Assets Accounted For As Secured Borrowings [Line Items]
Securities sold under agreements to repurchase	321,390,000
Overnight and Continuous | U.S. treasuries
Transfer Of Certain Financial Assets Accounted For As Secured Borrowings [Line Items]
Securities sold under agreements to repurchase	23,812,000
Overnight and Continuous | Government agency issued CMO
Transfer Of Certain Financial Assets Accounted For As Secured Borrowings [Line Items]
Securities sold under agreements to repurchase	297,578,000
Up to 30 Days
Transfer Of Certain Financial Assets Accounted For As Secured Borrowings [Line Items]
Securities sold under agreements to repurchase	10,939,000
Up to 30 Days | U.S. treasuries
Transfer Of Certain Financial Assets Accounted For As Secured Borrowings [Line Items]
Securities sold under agreements to repurchase	0
Up to 30 Days | Government agency issued CMO
Transfer Of Certain Financial Assets Accounted For As Secured Borrowings [Line Items]
Securities sold under agreements to repurchase	$ 10,939,000