Loans and Allowance for Loan Losses (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011
First mortgage loans:
Total first mortgage loans	$ 28,454,792	$ 29,040,116
Consumer and other loans:
Total consumer and other loans	276,506	287,229
Total loans	28,731,298	29,327,345
One- to four-family, Amortizing [Member]
First mortgage loans:
Total first mortgage loans	22,858,188	23,480,909
One- to four-family, Interest-only [Member]
First mortgage loans:
Total first mortgage loans	4,832,558	4,779,863
FHA/VA [Member]
First mortgage loans:
Total first mortgage loans	720,720	734,781
Multi-family and commercial mortgages [Member]
First mortgage loans:
Total first mortgage loans	38,657	39,634
Construction [Member]
First mortgage loans:
Total first mortgage loans	4,669	4,929
Fixed-rate second mortgages [Member]
Consumer and other loans:
Total consumer and other loans	124,826	131,597
Home equity credit lines [Member]
Consumer and other loans:
Total consumer and other loans	130,337	134,502
Other [Member]
Consumer and other loans:
Total consumer and other loans	$ 21,343	$ 21,130