Investment Securities Investment Securities Gains, Losses, and Proceeds (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended	9 Months Ended		12 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Investments, Debt and Equity Securities [Abstract]
Gross gains				$ 8,047	$ 1,159	$ 1,184
Gross losses				(4,009)	(690)	(690)
Investment securities gains, net	$ 2,796	$ 57		4,038	469	494
Proceeds from sales of investment securities			$ 1,000,000	1,066,957	$ 101,987	$ 102,011
Proceeds including Receivable from Sale of Available-for-sale Securities				$ 1,206,242