Investment Securities (Schedule Of Maturities Of Investment Securities) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2012
Investment Holdings [Line Items]
Available-for-sale Securities, Three months or less, Amortized Cost	$ 28,517
Available-for-sale Securities, Over three months through twelve months, Amortized Cost	335,264
Available-for-sale Securities, After one through five years, Amortized Cost	2,037,135
Available-for-sale Securities, After five through ten years, Amortized Cost	547,572
Available-for-sale Securities, After ten years, Amortized Cost	85,910
Available-for-sale Securities, Amortized Cost	3,036,357
Available-for-sale Securities, Three months or less, Fair Value	28,689
Available-for-sale Securities, Over three months through twelve months, Fair Value	340,008
Available-for-sale Securities, After one through five years, Fair Value	2,079,376
Available-for-sale Securities, After five through ten years, Fair Value	557,968
Available-for-sale Securities, After ten years, Fair Value	86,901
Available-for-sale Securities, Fair Value	3,095,009
Held-to-maturity Securities, Three months or less, Amortized Cost	85
Held-to-maturity Securities, Over three months through twelve months, Amortized Cost	245
Held-to-maturity Securities, After one through five years, Amortized Cost	345
Held-to-maturity Securities, After five through ten years, Amortized Cost	61
Held-to-maturity Securities, After ten years, Amortized Cost	3,889
Held-to-maturity Securities, Amortized Cost	4,625
Held-to-maturity Securities, Three months or less, Fair Value	85
Held-to-maturity Securities, Over three months through twelve months, Fair Value	246
Held-to-maturity Securities, After one through five years, Fair Value	348
Held-to-maturity Securities, After five through ten years, Fair Value	63
Held-to-maturity Securities, After ten years, Fair Value	3,994
Held-to-maturity Securities, Fair Value	4,736
Other Investments Securities [Member]
Investment Holdings [Line Items]
Available-for-sale Securities, Amortized Cost	1,959
Available-for-sale Securities, Fair Value	2,067
Held-to-maturity Securities, Amortized Cost
Held-to-maturity Securities, Fair Value