Securities (Details 3) (USD $)	3 Months Ended	9 Months Ended
	Sep. 30, 2014 security	Sep. 30, 2014 security	Sep. 30, 2013	Dec. 31, 2013 security
Securities
Number of securities held with unrealized loss	101	101		109
Proceeds from sales of securities from the available-for-sale portfolio		$ 14,447,000	$ 41,640,000
Gross realized gains from sale of available for sale securities	141,000	141,000	2,057,000
Total available-for-sale securities	366,026,000	366,026,000		401,690,000
Held-to-maturity, amortized cost	2,053,337,000	2,053,337,000		1,849,526,000
Held-to-maturity, fair value	2,035,378,000	2,035,378,000		1,811,122,000
Callable securities, amortized cost	189,600,000	189,600,000
Accrued interest receivable for securities	6,300,000	6,300,000		6,300,000
Available-for-sale debt securities, excluding mortgage-backed securities
Securities
Available-for-sale debt securities, amortized cost	98,700,000	98,700,000
Total available-for-sale securities	95,500,000	95,500,000
Held-to-maturity debt securities, excluding mortgage-backed securities
Securities
Held-to-maturity, amortized cost	91,500,000	91,500,000
Held-to-maturity, fair value	$ 89,000,000	$ 89,000,000