Note Borrowings (Notes payable) (Detail) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Others	$ 18,316	$ 18,642
Notes payable	1,564,204	1,536,356
Advances due 2018 To 2029 with fixed Rates 0.84% to 4.19%
Debt Instrument [Line Items]
Advances with the FHLB	599,954	572,307
Floating Rate from 0.22% to 0.34% over the 1 month LIBOR with maturities ranging from 2018 to 2019
Debt Instrument [Line Items]
Advances with the FHLB	34,164	34,164
Floating Rate from 0.09% to 0.24% over the 3 month LIBOR with maturities ranging from 2018 to 2019)
Debt Instrument [Line Items]
Advances with the FHLB	25,019	25,019
Fixed Rate 7.00% Percent Notes Due July 2019 paying interest semiannually, net of debt issuance costs of $2,606
Debt Instrument [Line Items]
Long Term Debt	447,394	446,873
Fixed Rate 6.125% to 8.327% Junior Subordinated Deferrable Interest Debentures Due 2027 to 2034, net of debt issuance costs of $443
Debt Instrument [Line Items]
Long Term Debt	$ 439,357	$ 439,351