Securities (Details 3) (USD $)	12 Months Ended
	Dec. 31, 2013 item	Dec. 31, 2012 item	Dec. 31, 2011
Securities
Number of securities held with unrealized loss	109	41
Proceeds from sales of securities available-for-sale	$ 41,640,000	$ 60,318,000	$ 0
Gross realized gains from sale of available for sale securities	2,057,000	8,477,000
Total available-for-sale securities	401,690,000	336,300,000
Held-to-maturity, amortized cost	1,849,526,000	1,700,141,000
Held-to-maturity, fair value	1,811,122,000	1,725,090,000
Callable securities, amortized cost	186,800,000
Accrued interest receivable for securities	6,300,000	5,700,000
Available-for-sale debt securities, excluding mortgage-backed securities
Securities
Available-for-sale debt securities, amortized cost	98,700,000
Total available-for-sale securities	91,200,000
Held-to-maturity debt securities, excluding mortgage-backed securities
Securities
Held-to-maturity, amortized cost	88,700,000
Held-to-maturity, fair value	$ 81,300,000