Securities (Details 3) (USD $)	3 Months Ended	6 Months Ended
	Jun. 30, 2013	Jun. 30, 2014 item	Jun. 30, 2013	Dec. 31, 2013 item
Securities
Number of securities held with unrealized loss		84		109
Proceeds from sales of securities from the available-for-sale portfolio		$ 0	$ 41,640,000
Gross realized gains from sale of available for sale securities	2,057,000		2,057,000
Total available-for-sale securities		392,439,000		401,690,000
Held-to-maturity, amortized cost		1,960,930,000		1,849,526,000
Held-to-maturity, fair value		1,950,622,000		1,811,122,000
Callable securities, amortized cost		189,600,000
Accrued interest receivable for securities		6,400,000		6,300,000
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		95,500,000
Held-to-maturity debt securities, excluding mortgage-backed securities
Securities
Held-to-maturity, amortized cost		91,500,000
Held-to-maturity, fair value		$ 88,800,000