Purchase Credit Impaired ("PCI") Loans - Rollforward of PCI Loans, Net of Allowance for Loan Losses (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Accretable Yield Movement Schedule [Roll Forward]
Balance at beginning of period	$ 83,693	$ 125,100
Principal reductions and interest payments	(19,315)	(25,261)
Accretion of loan discount	(8,604)	12,323
Changes in contractual and expected cash flows due to remeasurement	11,833	5,262
Reductions due to disposals	(12,418)	(19,106)
Balance at end of period	72,397	98,318
Contractual Cashflows
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Accretable Yield Movement Schedule [Roll Forward]
Balance at beginning of period	178,145	266,068
Principal reductions and interest payments	(19,315)	(25,261)
Accretion of loan discount	0	0
Changes in contractual and expected cash flows due to remeasurement	(5,731)	(2,616)
Reductions due to disposals	(19,734)	(30,334)
Balance at end of period	133,365	207,857
Non-accretable Difference
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Accretable Yield Movement Schedule [Roll Forward]
Balance at beginning of period	65,719	87,438
Principal reductions and interest payments	0	0
Accretion of loan discount	0	0
Changes in contractual and expected cash flows due to remeasurement	(26,797)	(7,378)
Reductions due to disposals	(4,183)	(7,379)
Balance at end of period	34,739	72,681
Accretable Yield
Certain Loans Acquired in Transfer Not Accounted for as Debt Securities, Accretable Yield Movement Schedule [Roll Forward]
Balance at beginning of period	28,733	53,530
Principal reductions and interest payments	0	0
Accretion of loan discount	8,604	12,323
Changes in contractual and expected cash flows due to remeasurement	9,233	(500)
Reductions due to disposals	(3,133)	(3,849)
Balance at end of period	$ 26,229	$ 36,858