Parent Statements of Financial Condition (Details) (USD $)	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Assets
Cash on hand and in banks	$ 109,995,000	$ 123,270,000
Interest bearing cash deposits	35,135,000	63,770,000
Cash and cash equivalents	155,657,000	187,040,000
Investment securities, available-for-sale	3,222,829,000	3,683,005,000
Other assets	55,251,000	41,969,000
Total assets	7,884,350,000	7,747,440,000
Liabilities and Stockholders' Equity
Subordinated debentures	125,562,000	125,418,000
Other liabilities	50,103,000	55,384,000
Total liabilities	6,921,100,000	6,846,491,000
Common stock	744,000	719,000
Paid-in capital	690,918,000	641,737,000
Retained earnings	261,943,000	210,531,000
Accumulated other comprehensive income	9,645,000	47,962,000
Total stockholders’ equity	963,250,000	900,949,000	850,227,000	838,204,000
Total liabilities and stockholders’ equity	7,884,350,000	7,747,440,000
Parent Company
Assets
Cash on hand and in banks	1,582,000	2,540,000
Interest bearing cash deposits	49,097,000	9,887,000
Cash and cash equivalents	50,679,000	12,427,000
Investment securities, available-for-sale	87,000	29,457,000
Other assets	9,050,000	23,221,000
Investment in subsidiaries	1,040,104,000	972,218,000
Total assets	1,099,920,000	1,037,323,000
Liabilities and Stockholders' Equity
Subordinated debentures	125,562,000	125,418,000
Other liabilities	11,108,000	10,956,000
Total liabilities	136,670,000	136,374,000
Common stock	744,000	719,000
Paid-in capital	690,918,000	641,737,000
Retained earnings	261,943,000	210,531,000
Accumulated other comprehensive income	9,645,000	47,962,000
Total stockholders’ equity	963,250,000	900,949,000
Total liabilities and stockholders’ equity	$ 1,099,920,000	$ 1,037,323,000