Loans and Allowance for Loan Losses (Details 1) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011
Loan portfolio by credit quality indicator
Performing	$ 27,666,713	$ 28,304,658
Non-performing	1,064,585	1,022,687
Total	28,731,298	29,327,345
Pass	27,532,729	28,165,532
Special mention	170,170	177,031
Substandard	1,028,399	984,782
Total	28,731,298	29,327,345
One- to four-family, Amortizing [Member]
Loan portfolio by credit quality indicator
Performing	22,765,110	23,417,785
Non-performing	813,798	797,905
Total	23,578,908	24,215,690
Pass	22,678,188	23,325,078
Special mention	140,223	146,391
Substandard	760,497	744,221
Total	23,578,908	24,215,690
One- to four-family, Interest-only [Member]
Loan portfolio by credit quality indicator
Performing	4,595,150	4,566,001
Non-performing	237,408	213,862
Total	4,832,558	4,779,863
Pass	4,563,706	4,536,090
Special mention	25,883	26,428
Substandard	242,969	217,345
Total	4,832,558	4,779,863
Multi-family and commercial mortgages [Member]
Loan portfolio by credit quality indicator
Performing	35,536	37,411
Non-performing	3,121	2,223
Total	38,657	39,634
Pass	23,068	23,997
Special mention	2,563	2,989
Substandard	13,026	12,648
Total	38,657	39,634
Construction [Member]
Loan portfolio by credit quality indicator
Performing	373	585
Non-performing	4,296	4,344
Total	4,669	4,929
Pass	80
Substandard	4,589	4,929
Total	4,669	4,929
Fixed-rate second mortgages [Member]
Loan portfolio by credit quality indicator
Performing	123,809	130,869
Non-performing	1,017	728
Total	124,826	131,597
Pass	123,511	130,649
Special mention	298	220
Substandard	1,017	728
Total	124,826	131,597
Home equity credit lines [Member]
Loan portfolio by credit quality indicator
Performing	126,392	130,897
Non-performing	3,945	3,605
Total	130,337	134,502
Pass	125,737	130,487
Special mention	655	410
Substandard	3,945	3,605
Total	130,337	134,502
Other [Member]
Loan portfolio by credit quality indicator
Performing	20,343	21,110
Non-performing	1,000	20
Total	21,343	21,130
Pass	18,439	19,231
Special mention	548	593
Substandard	2,356	1,306
Total	$ 21,343	$ 21,130