Investment Securities (Contractual Maturities and Narrative) (Details 2) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Available-for-sale Securities, Debt Maturities, Single Maturity Date, Amortized Cost Basis Rolling Maturity[Abstract]
Due in One Year or Less	$ 86,725
Due After One Year Through Five Years	585,928
Due After Five Years Through Ten Years	214,366
Due After Ten Years	31,629
Amortized Cost, Total	918,648
Available-for-sale Securities, Debt Maturities, Single Maturity Date, Rolling Maturities [Abstract]
Due in One Year or Less	86,878
Due After One Year Through Five Years	589,580
Due After Five Years Through Ten Years	223,309
Due After Ten Years	33,904
Fair Value, Total	933,671
Available-for-Sale: Amortized Cost	2,302,408	$ 2,183,943
Available-for-Sale: Fair Value	2,316,728	2,186,041
Held-to-maturity Securities, Debt Maturities, Single Maturity Date, Amortized Cost Basis, Rolling Maturities (Abstract]
Due in One Year or Less	235,104
Due After One Year Through Five Years	335,763
Due After Five Years Through Ten Years	258,942
Due After Ten Years	38,381
Amortized Cost, Total	868,190
Held-to-Maturity Securities, Debt Maturities, Single Maturity Date, Fair Value, Rolling Maturities [Abstract]
Due in One Year or Less	234,882
Due After One Year Through Five Years	338,517
Due After Five Years Through Ten Years	266,850
Due After Ten Years	41,219
Fair Value, Total	881,468
Held-to-Maturity: Amortized Cost	3,782,702
Held-to-Maturity: Fair Value	3,785,641	3,827,527
Carrying value of investment securities which were pledged to secure deposits of gov't entities and repos	2,700,000	2,400,000
Debt Securities Issued by Government Agencies
Available-for-sale Securities, Debt Maturities, Single Maturity Date, Rolling Maturities [Abstract]
Available-for-sale Securities, Debt Securities Issued by Government Agencies and Mortgage-Backed Securities: Amortized Cost	429,657
Available-for-sale Securities, Debt Securities Issued by Government Agencies and Mortgage-Backed Securities: Fair Value	432,436
Residential - Government Agencies
Available-for-sale Securities, Debt Maturities, Single Maturity Date, Rolling Maturities [Abstract]
Available-for-sale Securities, Debt Securities Issued by Government Agencies and Mortgage-Backed Securities: Amortized Cost	262,834
Available-for-sale Securities, Debt Securities Issued by Government Agencies and Mortgage-Backed Securities: Fair Value	265,542
Available-for-Sale: Amortized Cost	262,834	240,412
Available-for-Sale: Fair Value	265,542	243,844
Residential - U.S. Government-Sponsored Enterprises
Available-for-sale Securities, Debt Maturities, Single Maturity Date, Rolling Maturities [Abstract]
Available-for-sale Securities, Debt Securities Issued by Government Agencies and Mortgage-Backed Securities: Amortized Cost	613,512
Available-for-sale Securities, Debt Securities Issued by Government Agencies and Mortgage-Backed Securities: Fair Value	609,901
Available-for-Sale: Amortized Cost	613,512	511,234
Available-for-Sale: Fair Value	609,901	506,987
Commercial - Government Agencies
Available-for-sale Securities, Debt Maturities, Single Maturity Date, Rolling Maturities [Abstract]
Available-for-sale Securities, Debt Securities Issued by Government Agencies and Mortgage-Backed Securities: Amortized Cost	77,757
Available-for-sale Securities, Debt Securities Issued by Government Agencies and Mortgage-Backed Securities: Fair Value	75,178
Available-for-Sale: Amortized Cost	77,757	89,544
Available-for-Sale: Fair Value	75,178	85,517
Mortgage-Backed Securities
Available-for-sale Securities, Debt Maturities, Single Maturity Date, Rolling Maturities [Abstract]
Available-for-sale Securities, Debt Securities Issued by Government Agencies and Mortgage-Backed Securities: Amortized Cost	954,103
Available-for-sale Securities, Debt Securities Issued by Government Agencies and Mortgage-Backed Securities: Fair Value	950,621
Available-for-Sale: Amortized Cost	954,103	841,190
Available-for-Sale: Fair Value	950,621	836,348
Residential - Government Agencies
Held-to-Maturity Securities, Debt Maturities, Single Maturity Date, Fair Value, Rolling Maturities [Abstract]
Held-to-Maturity: Mortgage-Backed Securities: Amortized Cost	1,928,530
Held-to-Maturity: Mortgage-Backed Securities: Fair Value	1,924,654
Held-to-Maturity: Fair Value	1,924,654	1,936,782
Residential - U.S. Government-Sponsored Enterprises
Held-to-Maturity Securities, Debt Maturities, Single Maturity Date, Fair Value, Rolling Maturities [Abstract]
Held-to-Maturity: Mortgage-Backed Securities: Amortized Cost	772,212
Held-to-Maturity: Mortgage-Backed Securities: Fair Value	766,352
Held-to-Maturity: Fair Value	766,352	742,647
Commercial - Government Agencies
Held-to-Maturity Securities, Debt Maturities, Single Maturity Date, Fair Value, Rolling Maturities [Abstract]
Held-to-Maturity: Mortgage-Backed Securities: Amortized Cost	213,770
Held-to-Maturity: Mortgage-Backed Securities: Fair Value	213,167
Held-to-Maturity: Fair Value	213,167	230,364
Mortgage-Backed Securities
Held-to-Maturity Securities, Debt Maturities, Single Maturity Date, Fair Value, Rolling Maturities [Abstract]
Held-to-Maturity: Mortgage-Backed Securities: Amortized Cost	2,914,512
Held-to-Maturity: Mortgage-Backed Securities: Fair Value	2,904,173
Held-to-Maturity: Fair Value	$ 2,904,173	$ 2,909,793

The carrying value, as of the date of each statement of financial position presented, of investment securities, classified as available for sale or held to maturity, which are owned but transferred to serve as collateral to secure deposits of government entities and securities sold under agreements to repurchase, and payment of the related debt obligation, primarily a secured borrowing or repurchase agreement.

No definition available.