Note Borrowings (Notes payable) (Detail) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Debt Instrument [Line Items]
Others	$ 18,234	$ 18,642
Notes payable	1,561,663	1,536,356
Advances due 2018 To 2029 with fixed Rates 0.89% to 4.19%
Debt Instrument [Line Items]
Advances with the FHLB	602,262	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 0.12% to 0.24% over the 3 month LIBOR with maturities ranging from 2018 to 2019)
Debt Instrument [Line Items]
Advances with the FHLB	19,724	25,019
Fixed Rate 7.00% Percent Notes Due July 2019 paying interest semiannually, net of debt issuance costs of $2,085
Debt Instrument [Line Items]
Long Term Debt	447,915	446,873
Fixed Rate 6.125% to 8.327% Junior Subordinated Deferrable Interest Debentures Due 2027 to 2034, net of debt issuance costs of $436
Debt Instrument [Line Items]
Long Term Debt	$ 439,364	$ 439,351