Purchase Credit Impaired ("PCI") Loans - Rollforward of PCI Loans, Net of Allowance for Loan Losses (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 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	(6,148)	(9,849)
Accretion of loan discount	3,088	4,560
Changes in contractual and expected cash flows due to remeasurement	5,511	(539)
Reductions due to disposals	(2,981)	(9,113)
Balance at end of period	83,163	110,159
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	(6,148)	(9,849)
Accretion of loan discount	0	0
Changes in contractual and expected cash flows due to remeasurement	(12,159)	4,888
Reductions due to disposals	(5,623)	(14,297)
Balance at end of period	154,215	246,810
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	(26,187)	10,503
Reductions due to disposals	(1,709)	(3,142)
Balance at end of period	37,823	94,799
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	(3,088)	(4,560)
Changes in contractual and expected cash flows due to remeasurement	8,517	(5,076)
Reductions due to disposals	(933)	(2,042)
Balance at end of period	$ 33,229	$ 41,852