Investment Securities (Details Textuals) - USD ($) $ in Thousands	3 Months Ended			6 Months Ended	9 Months Ended		12 Months Ended
	Sep. 30, 2015	Jun. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Investments, Debt and Equity Securities [Abstract]
Proceeds from sales of investment securities				$ 1,000,000	$ 1,066,957	$ 101,987	$ 102,011
Federal Home Loan Bank Stock	$ 88,000			88,000	88,000		118,000
Federal Reserve Bank Stock	73,000			73,000	73,000		71,000
Investment securities gains, net	2,796		$ 57		4,038	469	494
Proceeds from the sale of FHLB stock		$ 43,000			42,514	0
Payments to Acquire Federal Home Loan Bank Stock		$ 14,000			14,279	$ 7,626
Proceeds including Receivable from Sale of Available-for-sale Securities					1,206,242
Unsettled trades to sell securities	$ 139,286			$ 139,286	$ 139,286		$ 0