Recent Developments Including Mergers and Acquisitions - Additional Information (Detail) (USD $)	0 Months Ended	1 Months Ended
	Jan. 19, 2012	Jun. 30, 2013	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Jul. 12, 2011 Fbc Financial Corporation [Member]	Jul. 12, 2011 1st Bank Oklahoma [Member]
Recent Transactions Including Mergers Acquisitions [Line Items]
Pretax gain on sale of investments	$ 4,500,000
Gain on sale of investments, Net of tax	2,600,000
Premium paid above equity capital						1,500,000
Total assets			6,038,974,000	6,022,250,000	5,608,825,000		217,000,000
Loans			3,348,112,000	3,203,702,000			116,000,000
Deposits			5,419,519,000	5,440,830,000			178,000,000
Equity capital			556,997,000	519,567,000	483,041,000		18,000,000
Prepaid deposit insurance				9,700,000
Refunds received for overpayment		$ 9,600,000