Nature of Operations and Summary of Significant Accounting Policies (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Assets
Loans receivable	$ 3,408,094	$ 3,466,135
Premises and equipment, net	159,386	158,872
Accrued interest receivable	39,359	34,961
Other assets	43,046	41,709
Total assets	7,632,205	7,187,906
Liabilities
Other borrowed funds	10,152	9,995
Accrued interest payable	4,654	5,825
Other liabilities	66,906	47,682
Total liabilities	6,742,048	6,337,679
CDE (NMTC) [Member]
Assets
Loans receivable	35,480	32,748
Accrued interest receivable	112	116
Other assets	1,167	1,439
Total assets	36,759	34,303
Liabilities
Other borrowed funds	4,629	4,629
Accrued interest payable	3	4
Other liabilities	92	186
Total liabilities	4,724	4,819
LIHTC [Member]
Assets
Premises and equipment, net	15,726	15,996
Other assets	143	31
Total assets	15,869	16,027
Liabilities
Other borrowed funds	3,639	3,306
Accrued interest payable	5	9
Other liabilities	148	363
Total liabilities	$ 3,792	$ 3,678