Fair Value Measurement (Details) (USD $) In Thousands	Jun. 30, 2011	Dec. 31, 2010
Recurring Fair Value Measurements
Residential loans held for sale	$ 22,951	$ 41,340
Derivative assets	47,809	47,764
Derivative liabilities	72,037	72,824
True-up liability	12,196	12,061
Level 1 [Member] | Recurring [Member]
Recurring Fair Value Measurements
Available for sale securities	3,752
Residential loans held for sale	0
Derivative assets	0
Total assets at fair value on a recurring and nonrecurring basis	3,752
Derivative liabilities	0
True-up liability	0
Total liabilities at fair value on a recurring basis	0
Level 2 [Member] | Recurring [Member]
Recurring Fair Value Measurements
Available for sale securities	3,349,950
Residential loans held for sale	22,951
Derivative assets	47,809
Total assets at fair value on a recurring and nonrecurring basis	3,420,710
Derivative liabilities	72,037
True-up liability	0
Total liabilities at fair value on a recurring basis	72,037
Level 3 [Member] | Recurring [Member]
Recurring Fair Value Measurements
Available for sale securities	144,570
Residential loans held for sale	0
Derivative assets	0
Total assets at fair value on a recurring and nonrecurring basis	144,570
Derivative liabilities	0
True-up liability	12,196
Total liabilities at fair value on a recurring basis	12,196
Recurring [Member]
Recurring Fair Value Measurements
Available for sale securities	3,498,272
Residential loans held for sale	22,951
Derivative assets	47,809
Total assets at fair value on a recurring and nonrecurring basis	3,569,032
Derivative liabilities	72,037
True-up liability	12,196
Total liabilities at fair value on a recurring basis	$ 84,233