Securities Part 6 (Details) (USD $)	3 Months Ended		12 Months Ended
	Mar. 31, 2012	Mar. 31, 2011	Dec. 31, 2011
Securities [Abstract]
Taxable equivalent basis - effective tax rate (in hundredths)	39.00%
Average expected Life of Mortgage Backed Security (in years)	2.3
Securities Pledged as Collateral, Amortized Cost	$ 4,000,000,000	$ 3,900,000,000	$ 4,400,000,000
Estimated Unemployment Rate , Maximum (in hundredths)	9.50%
Estimated Unemployment Rate, Minimum (in hundredths)	8.00%
Estimated housing price depreciation, Next Twelve Months (in hundredths)	8.00%
Estimated housing price growth per year, Thereafter (in hundredths)	2.00%
Discount Rate Used To Estimate Cash Flow, Minimum (in hundredths)	2.00%
Discount Rate Used To Estimate Cash Flow, Maximum (in hundredths)	6.25%
Distribution of Amortized Cost and Fair Value for Below Investment Grade Residential Mortgage-Backed Securities [Abstract]
Number of Securities	49
Amortized Cost	371,045,000
Fair Value	326,513,000
Credit Losses Recognized [Abstract]
Number of Securities in Current Period	21
Amount of Credit Losses Recognized in Current Period	3,722,000
Number of Securities in Life-to-Date	47
Amount of Credit Losses Recognized in Life-to-Date	69,480,000
Fair value option securities [Abstract]
Fair value, fair value option securities	347,952,000	326,624,000	651,226,000
Net unrealized gain (loss), fair value option securities	2,271,000	(3,698,000)	19,251,000
Jumbo A Loans [Member]
Distribution of Amortized Cost and Fair Value for Below Investment Grade Residential Mortgage-Backed Securities [Abstract]
Number of Securities	33
Amortized Cost	230,903,000
Fair Value	206,326,000
Credit Losses Recognized [Abstract]
Number of Securities in Current Period	12
Amount of Credit Losses Recognized in Current Period	763,000
Number of Securities in Life-to-Date	31
Amount of Credit Losses Recognized in Life-to-Date	22,802,000
US Government Agencies Debt Securities [Member]
Fair value option securities [Abstract]
Fair value, fair value option securities	322,180,000	326,624,000	626,109,000
Net unrealized gain (loss), fair value option securities	1,593,000	(3,698,000)	19,233,000
Private Issue [Member]
Fair value option securities [Abstract]
Fair value, fair value option securities	25,772,000	0	25,117,000
Net unrealized gain (loss), fair value option securities	678,000	0	18,000
Below Investment Grade [Member] | Alt A [Member]
Distribution of Amortized Cost and Fair Value for Below Investment Grade Residential Mortgage-Backed Securities [Abstract]
Number of Securities	16
Amortized Cost	140,142,000
Fair Value	120,187,000
Credit Losses Recognized [Abstract]
Number of Securities in Current Period	9
Amount of Credit Losses Recognized in Current Period	2,959,000
Number of Securities in Life-to-Date	16
Amount of Credit Losses Recognized in Life-to-Date	$ 46,678,000