Securities Part 4 (Details) (Available-for-sale Securities [Member], USD $) In Thousands, unless otherwise specified	3 Months Ended	6 Months Ended
	Jun. 30, 2012	Jun. 30, 2012	Dec. 31, 2011	Jun. 30, 2011
Distribution of Amortized Cost and Fair Value For Below Investment Grade Residential Mortgage-Backed Securities [Abstract]
Available-for-sale Securities, Amortized Cost Basis	$ 10,153,162	$ 10,153,162	$ 9,957,205	$ 9,303,808
Available-for-Sale Securities, Fair Value	10,395,415	10,395,415	10,179,365	9,567,008
Residential Mortgage Backed Securities [Member]
Distribution of Amortized Cost and Fair Value For Below Investment Grade Residential Mortgage-Backed Securities [Abstract]
Available-for-sale Securities, Amortized Cost Basis	9,986,158	9,986,158	9,800,457	9,170,211
Available-for-Sale Securities, Fair Value	10,221,293	10,221,293	10,007,343	9,407,011
Mortgage-backed Securities, Issued by Private Enterprises [Member] | Residential Mortgage Backed Securities [Member]
Distribution of Amortized Cost and Fair Value For Below Investment Grade Residential Mortgage-Backed Securities [Abstract]
Number of Securities	49	49
Available-for-sale Securities, Amortized Cost Basis	354,183	354,183	503,068	581,303
Amortized Cost	354,183	354,183
Fair Value	317,761	317,761
Available-for-Sale Securities, Fair Value	317,761	317,761	419,166	513,222
Credit losses Recognized [Abstract]
Number of Securities in Current Period	5
Amount of Credit Losses Recognized in Current Period	858
Number of Securities in Life-to-Date	47	47
Amount of Credit Losses Recognized in Life-to-Date		70,338
Mortgage-backed Securities, Issued by Private Enterprises [Member] | Residential Mortgage Backed Securities [Member] | Alt A [Member]
Distribution of Amortized Cost and Fair Value For Below Investment Grade Residential Mortgage-Backed Securities [Abstract]
Number of Securities	16	16
Available-for-sale Securities, Amortized Cost Basis	134,266	134,266	168,461	195,932
Available-for-Sale Securities, Fair Value	118,414	118,414	132,242	166,757
Credit losses Recognized [Abstract]
Number of Securities in Current Period	3
Amount of Credit Losses Recognized in Current Period	739
Number of Securities in Life-to-Date	16	16
Amount of Credit Losses Recognized in Life-to-Date		47,417
Mortgage-backed Securities, Issued by Private Enterprises [Member] | Residential Mortgage Backed Securities [Member] | Jumbo A Loans [Member]
Distribution of Amortized Cost and Fair Value For Below Investment Grade Residential Mortgage-Backed Securities [Abstract]
Number of Securities	33	33
Available-for-sale Securities, Amortized Cost Basis	219,917	219,917	334,607	385,371
Available-for-Sale Securities, Fair Value	199,347	199,347	286,924	346,465
Credit losses Recognized [Abstract]
Number of Securities in Current Period	2
Amount of Credit Losses Recognized in Current Period	119
Number of Securities in Life-to-Date	31	31
Amount of Credit Losses Recognized in Life-to-Date		$ 22,921