Loans and Allowance for Loan Losses (Impaired Loans) (Details) - USD ($) $ in Thousands		3 Months Ended	12 Months Ended
		Mar. 31, 2016	Dec. 31, 2014	Dec. 31, 2015
Recorded Investment
Impaired loans, no individually reviewed for impairment		$ 5,009		$ 4,903
Impaired loans, individually reviewed, with no impairment		20,548		22,411
Impaired loans, individually reviewed, with impairment		4,525		3,817
Total impaired loans, excluding purchased impaired	[1]	30,082		31,131
Purchased impaired loans with subsequent deterioration		81,519		84,329
Purchased impaired loans with no subsequent deterioration		3,108		3,235
Impaired financing receivable, simple average balance		30,607	$ 35,290
Associated Reserves
Impaired loan, individually reviewed, with impairment, associated reserves	[1]	384		399
Purchased impaired loans with subsequent deterioration		2,754		2,754
Impaired financing receivable, including deteriorated loans purchased, related allowance		$ 3,138		$ 3,153

[1] * Included at March 31, 2016 and December 31, 2015 were $11.7 million and $13.1 million, respectively, in restructured and performing loans.