Investment Securities, AFS and HTM Contractual Maturities (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Amortized Cost
Available for Sale, Due in one year or less	$ 1,500
Available for Sale, Due after one year through five years	4,204
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	5,704
Investment securities available for sale, amortized cost	3,713,769	$ 4,724,895
Fair Value
Available for Sale, Due in one year or less	1,506
Available for Sale, Due after one year through five years	4,175
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	5,681
Investment securities available for sale, at fair value	$ 3,687,470	4,680,226
Ratio of Fair Value to Amortized Cost	99.30%
Amortized Cost
Held to Maturity, Due in one year or less	$ 41,085
Held to Maturity, Due after one year through five years	239,986
Held to Maturity, Due after five years through ten years	261,149
Held to Maturity, Due after ten years	620,700
Held to Maturity, Debt Securities, Amortized Cost Basis	1,162,920
Held to Maturity Amortized Cost	2,255,395	1,273,536
Fair Value
Held to Maturity, Due in one year or less	33,447
Held to Maturity, Due after one year through five years	246,760
Held to Maturity, Due after five years through ten years	265,255
Held to Maturity, Due after ten years	626,904
Held to Maturity, Securities, Debt Securities	1,172,366
Held to Maturity, Total debt securities	$ 2,263,322	1,264,674
Ratio of Fair Value to Amortized Cost	100.40%
Private Label
Amortized Cost
Investment securities available for sale, amortized cost	$ 1,102	1,134
Fair Value
Investment securities available for sale, at fair value	1,086	1,121
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	1,443,501	2,064,508
Fair Value
Investment securities available for sale, at fair value	1,419,872	2,028,898
Amortized Cost
Held to Maturity Amortized Cost	575,383
Fair Value
Held to Maturity, Total debt securities	573,166
Equity Securities [Member]
Amortized Cost
Investment securities available for sale, amortized cost	18
Fair Value
Investment securities available for sale, at fair value	128
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	534,058	625,234
Fair Value
Investment securities available for sale, at fair value	546,525	639,930
Amortized Cost
Held to Maturity Amortized Cost	43,575	37,697
Fair Value
Held to Maturity, Total debt securities	43,439	37,443
GNMA \| Residential Related Securities
Amortized Cost
Investment securities available for sale, amortized cost	1,729,386	2,028,301
Fair Value
Investment securities available for sale, at fair value	1,714,178	2,004,475
Amortized Cost
Held to Maturity Amortized Cost	473,517	89,996
Fair Value
Held to Maturity, Total debt securities	$ 474,351	$ 89,556

Held-to-maturity Debt Securities, Amortized Cost Basis

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