Investment Securities (Summary Of Investment Securities) (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Investment [Line Items]
Held-to-maturity, fair value	$ 850,473	$ 552,088
Held-to-maturity, Amortized cost	867,904
Available-for-sale debt securities, Amortized cost	13,336,309
Available-for-sale debt securities, Gross unrealized gains, Recognized in OCI	18,445
Available-for-sale debt securities, Gross unrealized losses, Recognized in OCI	166,976
Available-for-sale debt securities, Estimated fair value	13,187,778	7,542,480
Available-for-sale equity securities, Gross unrealized gains, Recognized in OCI		27,163
Available-for-sale equity securities, Gross unrealized losses, Recognized in OCI		56,661
Available-for-sale, at fair value	13,372,194	7,643,116
Available-for-sale Equity Securities, Amortized Cost Basis		7,571,978
Available-for-sale Securities, Amortized Cost Basis	13,520,716	7,672,590
Available-for-sale, Gross unrealized gains, Recognized in OCI	18,454	27,224
Available-for-sale, Gross unrealized losses, Recognized in OCI	166,976	56,698
amortized cost of investment securities	14,388,620	8,218,238
Gross Unrealized Gains of Investment Securities Recognized in OCI	24,429	38,442
Gross Unrealized Losses of Investment Securities Recognized in OCI	190,382	61,476
Estimated Fair Value of Investment Securities	14,222,667	8,195,204
Held-to-maturity Securities	867,904	545,648
Municipal Securities [Member]
Investment [Line Items]
Held-to-maturity, fair value	850,473	552,088
Held To Maturity Securities Gross Unrealized Losses	23,406	4,778
Held-to-maturity, Amortized cost	867,904	545,648
Held To Maturity Securities Gross Unrealized Gains	5,975	11,218
Available-for-sale debt securities, Amortized cost	1,181,560	417,374
Available-for-sale debt securities, Gross unrealized gains, Recognized in OCI	969	2,177
Available-for-sale debt securities, Gross unrealized losses, Recognized in OCI	28,319	856
Available-for-sale debt securities, Estimated fair value	1,154,210	418,695
Available-for-sale, Other debt securities [Member]
Investment [Line Items]
Available-for-sale debt securities, Amortized cost	25,359
Available-for-sale debt securities, Gross unrealized gains, Recognized in OCI	103
Available-for-sale debt securities, Gross unrealized losses, Recognized in OCI	1,570
Available-for-sale debt securities, Estimated fair value	23,892
Other [Member] | Asset-Backed Securities [Member]
Investment [Line Items]
Available-for-sale equity securities, Gross unrealized gains, Recognized in OCI		152
Available-for-sale equity securities, Gross unrealized losses, Recognized in OCI		2,665
Available-for-sale, at fair value		22,941
Available-for-sale Equity Securities, Amortized Cost Basis		25,454
Agency Securities [Member]
Investment [Line Items]
Available-for-sale debt securities, Amortized cost	1,845,825	1,231,740
Available-for-sale debt securities, Gross unrealized gains, Recognized in OCI	2,338	4,313
Available-for-sale debt securities, Gross unrealized losses, Recognized in OCI	9,188	2,658
Available-for-sale debt securities, Estimated fair value	1,838,975	1,233,395
Agency Guaranteed Mortgage-Backed Securities [Member]
Investment [Line Items]
Available-for-sale debt securities, Amortized cost	7,985,630	3,964,593
Available-for-sale debt securities, Gross unrealized gains, Recognized in OCI	6,596	7,919
Available-for-sale debt securities, Gross unrealized losses, Recognized in OCI	109,392	36,037
Available-for-sale debt securities, Estimated fair value	7,882,834	3,936,475
Small Business Administration Loan-Backed Securities [Member]
Investment [Line Items]
Available-for-sale debt securities, Amortized cost	2,297,935	1,932,817
Available-for-sale debt securities, Gross unrealized gains, Recognized in OCI	8,439	12,602
Available-for-sale debt securities, Gross unrealized losses, Recognized in OCI	18,507	14,445
Available-for-sale debt securities, Estimated fair value	2,287,867	1,930,974
Mutual Funds And Other [Member]
Investment [Line Items]
Available-for-sale, at fair value		100,636
Available-for-sale Securities, Amortized Cost Basis		100,612
Available-for-sale, Gross unrealized gains, Recognized in OCI		61
Available-for-sale, Gross unrealized losses, Recognized in OCI		$ 37
Mutual Funds And Stock [Member]
Investment [Line Items]
Available-for-sale, at fair value	184,416
Available-for-sale Securities, Amortized Cost Basis	184,407
Available-for-sale, Gross unrealized gains, Recognized in OCI	9
Available-for-sale, Gross unrealized losses, Recognized in OCI	$ 0