Loans Receivable and Allowance for Loan Losses (Details 5) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Recorded Investment
Total	$ 12,847,705	$ 13,155,914
Residential Mortgage Loans | Interest-only loans
Recorded Investment
Total	2,873,253
Residential Mortgage Loans | Interest-only loans | Within one year
Recorded Investment
Total	205,246
Residential Mortgage Loans | Interest-only loans | More than one year to three years
Recorded Investment
Total	1,388,990
Residential Mortgage Loans | Interest-only loans | More than three years to five years
Recorded Investment
Total	1,084,140
Residential Mortgage Loans | Interest-only loans | Over five years
Recorded Investment
Total	$ 194,877