Investment Securities - Additional Information (Details) (USD $) In Thousands, unless otherwise specified			9 Months Ended
	Sep. 30, 2013	Dec. 31, 2012	Sep. 30, 2013 Maximum	Sep. 30, 2013 Minimum	Sep. 30, 2013 Trust Preferred Securities	Sep. 30, 2013 Trust Preferred Securities Maximum
Schedule of Available for sale Securities and Held to maturity Securities [Line Items]
Carrying value of securities pledged as collateral	$ 375,411	$ 335,775
Book value of securities sold under agreements to repurchase	111,138	128,094
Investment amortized cost	917,975	859,124			6,300
Fair value of investments					$ 453
Percentage of fair value of investments						1.00%
Spread over LIBOR			1.57%	0.85%