Fair Value of Financial Instruments - Hierarchy Table - Recurring Basis (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
Fair Value Disclosures
Investment securities available-for-sale, at fair value	$ 863,243	$ 787,429
Agency
Fair Value Disclosures
Investment securities available-for-sale, at fair value	44,164	47,209
Corporate
Fair Value Disclosures
Investment securities available-for-sale, at fair value	104,406	79,546
Municipal bonds
Fair Value Disclosures
Investment securities available-for-sale, at fair value	223,657	232,128
Collateralized mortgage obligation: residential
Fair Value Disclosures
Investment securities available-for-sale, at fair value	31,709	33,781
Mortgage-backed securities: residential
Fair Value Disclosures
Investment securities available-for-sale, at fair value	459,307	394,765
Level 1
Fair Value Disclosures
Investment securities available-for-sale, at fair value	0	0
Level 2
Fair Value Disclosures
Investment securities available-for-sale, at fair value	863,243	787,429
Level 3
Fair Value Disclosures
Investment securities available-for-sale, at fair value	0	0
Recurring basis
Fair Value Disclosures
Investment securities available-for-sale, at fair value	863,243	787,429
Recurring basis | Agency
Fair Value Disclosures
Investment securities available-for-sale, at fair value	44,164	47,209
Recurring basis | Corporate
Fair Value Disclosures
Investment securities available-for-sale, at fair value	104,406	79,546
Recurring basis | Municipal bonds
Fair Value Disclosures
Investment securities available-for-sale, at fair value	223,657	232,128
Recurring basis | Collateralized mortgage obligation: residential
Fair Value Disclosures
Investment securities available-for-sale, at fair value	31,709	33,781
Recurring basis | Mortgage-backed securities: residential
Fair Value Disclosures
Investment securities available-for-sale, at fair value	459,307	394,765
Recurring basis | Level 1
Fair Value Disclosures
Investment securities available-for-sale, at fair value	0	0
Recurring basis | Level 1 | Agency
Fair Value Disclosures
Investment securities available-for-sale, at fair value	0	0
Recurring basis | Level 1 | Corporate
Fair Value Disclosures
Investment securities available-for-sale, at fair value	0	0
Recurring basis | Level 1 | Municipal bonds
Fair Value Disclosures
Investment securities available-for-sale, at fair value	0	0
Recurring basis | Level 1 | Collateralized mortgage obligation: residential
Fair Value Disclosures
Investment securities available-for-sale, at fair value	0	0
Recurring basis | Level 1 | Mortgage-backed securities: residential
Fair Value Disclosures
Investment securities available-for-sale, at fair value	0	0
Recurring basis | Level 2
Fair Value Disclosures
Investment securities available-for-sale, at fair value	863,243	787,429
Recurring basis | Level 2 | Agency
Fair Value Disclosures
Investment securities available-for-sale, at fair value	44,164	47,209
Recurring basis | Level 2 | Corporate
Fair Value Disclosures
Investment securities available-for-sale, at fair value	104,406	79,546
Recurring basis | Level 2 | Municipal bonds
Fair Value Disclosures
Investment securities available-for-sale, at fair value	223,657	232,128
Recurring basis | Level 2 | Collateralized mortgage obligation: residential
Fair Value Disclosures
Investment securities available-for-sale, at fair value	31,709	33,781
Recurring basis | Level 2 | Mortgage-backed securities: residential
Fair Value Disclosures
Investment securities available-for-sale, at fair value	459,307	394,765
Recurring basis | Level 3
Fair Value Disclosures
Investment securities available-for-sale, at fair value	0	0
Recurring basis | Level 3 | Agency
Fair Value Disclosures
Investment securities available-for-sale, at fair value	0	0
Recurring basis | Level 3 | Corporate
Fair Value Disclosures
Investment securities available-for-sale, at fair value	0	0
Recurring basis | Level 3 | Municipal bonds
Fair Value Disclosures
Investment securities available-for-sale, at fair value	0	0
Recurring basis | Level 3 | Collateralized mortgage obligation: residential
Fair Value Disclosures
Investment securities available-for-sale, at fair value	0	0
Recurring basis | Level 3 | Mortgage-backed securities: residential
Fair Value Disclosures
Investment securities available-for-sale, at fair value	$ 0	$ 0