Investments (Unrealized Losses) (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Investment securities available for sale:
Fair Value, Less than 12 months	$ 1,107,272	$ 3,104,700
Unrealized Losses, Less than 12 months	2,359	43,715
Fair Value, 12 months or more	1,109,829	56,830
Available For Sale Securities Continuous Unrealized Loss Position 12 Months Or Longer Aggregate Losses Acumulated In Investments	15,135	1,105
Fair Value, Total	2,217,101	3,161,530
Unrealized Losses, Total	17,494	44,820
U. S. Treasury
Investment securities available for sale:
Fair Value, Less than 12 months	135,712	102,105
Unrealized Losses, Less than 12 months	18	45
Fair Value, 12 months or more	0	0
Available For Sale Securities Continuous Unrealized Loss Position 12 Months Or Longer Aggregate Losses Acumulated In Investments	0	0
Fair Value, Total	135,712	102,105
Unrealized Losses, Total	18	45
Government Agency
Investment securities available for sale:
Fair Value, Less than 12 months	242,563	780,552
Unrealized Losses, Less than 12 months	178	761
Fair Value, 12 months or more	0	29,969
Available For Sale Securities Continuous Unrealized Loss Position 12 Months Or Longer Aggregate Losses Acumulated In Investments	0	31
Fair Value, Total	242,563	810,521
Unrealized Losses, Total	178	792
Mortgage Backed Securities, Other [Member]
Investment securities available for sale:
Fair Value, Less than 12 months	728,997	2,221,213
Unrealized Losses, Less than 12 months	2,163	42,876
Fair Value, 12 months or more	1,109,829	26,861
Available For Sale Securities Continuous Unrealized Loss Position 12 Months Or Longer Aggregate Losses Acumulated In Investments	15,135	1,074
Fair Value, Total	1,838,826	2,248,074
Unrealized Losses, Total	17,298	43,950
Other Debt Obligations
Investment securities available for sale:
Fair Value, Less than 12 months		830
Unrealized Losses, Less than 12 months		33
Fair Value, 12 months or more		0
Available For Sale Securities Continuous Unrealized Loss Position 12 Months Or Longer Aggregate Losses Acumulated In Investments		0
Fair Value, Total		830
Unrealized Losses, Total		33
State, County and Municipal
Investment securities available for sale:
Unrealized Losses, Total	$ 0	$ 0