Recent Developments Including Mergers and Acquisitions (Details) (USD $)	6 Months Ended
	Jun. 30, 2012	Dec. 31, 2011	Jun. 30, 2011	Jun. 29, 2011
Pretax gain on sale of investments	$ 4,500,000
Gain on sale of investments, Net of tax	2,600,000
Gain on sale of investments, Net of tax shares	$ 0.17
Total assets	5,671,711,000	5,608,825,000	5,267,445,000	10,000,000,000
Loans	3,028,003,000	2,975,842,000	2,824,752,000
Deposits	5,099,648,000	5,037,735,000	4,701,999,000
Equity capital	499,561,000	483,041,000	470,397,000
Recent Transactions Including Mergers Acquisitions (Textual) [Abstract]
Interchange rate				0.21
Basis points	0.05%
FBC Financial Corporation [Member]
Premium paid above equity capital	1,500,000
1st Bank Oklahoma [Member]
Total assets	217,000,000
Loans	116,000,000
Deposits	178,000,000
Equity capital	$ 18,000,000