Securities (Details)		3 Months Ended		9 Months Ended
		Sep. 30, 2015 USD ($)	Sep. 30, 2014 USD ($)	Sep. 30, 2015 USD ($) security	Sep. 30, 2014 USD ($) security	Dec. 31, 2014 USD ($)
Securities (Details) - Securities Portfolio [Line Items]
Available-for-sale securities pledged as collateral		$ 1,000,000,000		$ 1,000,000,000		$ 779,400,000
Held-to-maturity securities pledged as collateral		0		0		$ 0
Reduction for sales of securities	[1],[2]	$ 0	$ 0	$ (171,000)	$ (8,570,000)
Collateralized Mortgage Obligations
Securities (Details) - Securities Portfolio [Line Items]
Number of securities sold that previously had other than temporary impairment | security				1
Carrying value of securities sold that previously had other than temporary impairment				$ 1,300,000
Trust-preferred collateralized debt obligations
Securities (Details) - Securities Portfolio [Line Items]
Number of securities sold that previously had other than temporary impairment | security					1
Carrying value of securities sold that previously had other than temporary impairment					$ 1,300,000

[1] During the nine months ended September 30, 2015, the Company sold one CMO with a carrying value of $1.3 million that had OTTI of $171,000 that was previously recognized in earnings. The Company sold one CDO with a carrying value of $1.3 million during the nine months ended September 30, 2014 that had OTTI of $8.6 million that was previously recognized in earnings

[2] Included in net securities gains in the Condensed Consolidated Statements of Income.