Securities - Contractual Maturities of Securities (Details) - USD ($)	3 Months Ended	12 Months Ended
	Mar. 31, 2017	Dec. 31, 2016
Available-for-sale, Amortized Cost
Due in one year or less	$ 40,045,000
Due after one year through five years	151,627,000
Due after ten years	75,000,000
Total	266,672,000
Available-for-sale, Amortized Cost	558,323,000	$ 275,734,000
Available-for-sale, Fair Value
Due in one year or less	40,009,000
Due after one year through five years	151,167,000
Due after five years through ten years	74,933,000
Total	266,109,000
Available-for-sale Securities, Total	555,632,000	274,619,000
Held-to-maturity, Amortized Cost
Held-to-maturity, Amortized Cost	33,836,000	35,505,000
Held-to-maturity, Fair Value
Held-to-maturity, Fair Value	33,246,000	34,844,000
Proceeds from sale of securities
Proceeds from Sale and Maturity of Marketable Securities	0	0
Impairment loss realized in consolidated statements of income	0
Mortgage-backed securities and collateralized mortgage obligations
Available-for-sale, Amortized Cost
Amortized cost	280,411,000
Available-for-sale, Fair Value
Fair value	278,582,000
Held-to-maturity, Amortized Cost
Debt maturities without single maturity date	33,836,000
Held-to-maturity, Fair Value
Debt maturities without single maturity date	33,246,000
CRA qualified investment fund
Available-for-sale, Amortized Cost
Amortized cost	11,240,000
Available-for-sale, Amortized Cost	11,240,000	11,183,000
Available-for-sale, Fair Value
Fair value	10,941,000
Available-for-sale Securities, Total	$ 10,941,000	$ 10,913,000