Investment Securities, AFS and HTM Contractual Maturities (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Amortized Cost
Available for Sale, Due in one year or less	$ 3,001
Available for Sale, Due after one year through five years	1,000
Available for Sale, Due after five years through ten years	0
Available for Sale, Due after ten years	0
Available for Sale, Total debt securities	4,001
Investment securities available for sale, amortized cost	4,377,443	$ 4,100,417
Fair Value
Available for Sale, Due in one year or less	2,996
Available for Sale, Due after one year through five years	1,000
Available for Sale, Due after five years through ten years	0
Available for Sale, Due after ten years	0
Available for Sale, Total debt securities	3,996
Investment securities available for sale, at fair value	$ 4,261,651	4,043,446
Ratio of Fair Value to Amortized Cost	97.40%
Amortized Cost
Held to Maturity, Due in one year or less	$ 46,938
Held to Maturity, Due after one year through five years	200,725
Held to Maturity, Due after five years through ten years	366,997
Held to Maturity, Due after ten years	978,487
Held to Maturity, Debt Securities, Amortized Cost Basis	1,593,147
Held to Maturity Amortized Cost	2,602,247	2,282,853
Fair Value
Held to Maturity, Due in one year or less	47,269
Held to Maturity, Due after one year through five years	199,266
Held to Maturity, Due after five years through ten years	361,260
Held to Maturity, Due after ten years	972,504
Held to Maturity, Securities, Debt Securities	1,580,300
Held to Maturity, Total debt securities	$ 2,560,943	2,283,574
Ratio of Fair Value to Amortized Cost	98.40%
Private Label
Amortized Cost
Investment securities available for sale, amortized cost	$ 1,037	1,067
Fair Value
Investment securities available for sale, at fair value	1,031	1,059
Amortized Cost
Held to Maturity Amortized Cost	0
Fair Value
Held to Maturity, Total debt securities	0
GNMA Commercial Mortgage-Related Securities
Amortized Cost
Investment securities available for sale, amortized cost	1,400,680	1,547,173
Fair Value
Investment securities available for sale, at fair value	1,348,282	1,513,277
Amortized Cost
Held to Maturity Amortized Cost	523,103
Fair Value
Held to Maturity, Total debt securities	507,813
Asset backed Securities
Amortized Cost
Investment securities available for sale, amortized cost	298,263
Fair Value
Investment securities available for sale, at fair value	299,831
Amortized Cost
Held to Maturity Amortized Cost	0
Fair Value
Held to Maturity, Total debt securities	0
Equity Securities [Member]
Amortized Cost
Investment securities available for sale, amortized cost	1,613	1,519
Fair Value
Investment securities available for sale, at fair value	1,613	1,632
Amortized Cost
Held to Maturity Amortized Cost	0
Fair Value
Held to Maturity, Total debt securities	0
FNMA and FHLMC \| Residential Related Securities
Amortized Cost
Investment securities available for sale, amortized cost	396,368	457,680
Fair Value
Investment securities available for sale, at fair value	396,709	464,768
Amortized Cost
Held to Maturity Amortized Cost	97,822	40,995
Fair Value
Held to Maturity, Total debt securities	95,707	40,904
GNMA \| Residential Related Securities
Amortized Cost
Investment securities available for sale, amortized cost	2,275,481	1,944,453
Fair Value
Investment securities available for sale, at fair value	2,210,189	1,913,350
Amortized Cost
Held to Maturity Amortized Cost	388,174	414,440
Fair Value
Held to Maturity, Total debt securities	$ 377,123	410,740
GNMA \| GNMA Commercial Mortgage-Related Securities
Amortized Cost
Held to Maturity Amortized Cost		546,098
Fair Value
Held to Maturity, Total debt securities		$ 539,888

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Namespace Prefix:	us-gaap_
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- Definition

Fair value of investment in debt security measured at amortized cost (held-to-maturity).

+ References

+ Details

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- Details

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- Details

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- Details

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- Details

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- Details

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- Details

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- Details

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