Fair Value Measurements - Measured at Fair Value on Recurring Basis (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	$ 419,300	$ 400,144
U.S. government agency securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	16,490	21,649
State, county and municipals
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	147,786	160,526
Mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	171,877	131,644
Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	83,147	86,325
Fair Value Measurements Using Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0	0
Fair Value Measurements Using Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	416,470	391,654
Fair Value Measurements Using Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	2,830	8,490
Recurring basis fair value measurements
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	419,300	400,144
Recurring basis fair value measurements | U.S. government agency securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	16,490	21,649
Recurring basis fair value measurements | State, county and municipals
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	147,786	160,526
Recurring basis fair value measurements | Mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	171,877	131,644
Recurring basis fair value measurements | Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	83,147	86,325
Recurring basis fair value measurements | Other investments (equity securities)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments (equity securities)	4,080	2,650
Recurring basis fair value measurements | Fair Value Measurements Using Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0	0
Recurring basis fair value measurements | Fair Value Measurements Using Level 1 | U.S. government agency securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0	0
Recurring basis fair value measurements | Fair Value Measurements Using Level 1 | State, county and municipals
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0	0
Recurring basis fair value measurements | Fair Value Measurements Using Level 1 | Mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0	0
Recurring basis fair value measurements | Fair Value Measurements Using Level 1 | Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0	0
Recurring basis fair value measurements | Fair Value Measurements Using Level 1 | Other investments (equity securities)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments (equity securities)	4,080	2,650
Recurring basis fair value measurements | Fair Value Measurements Using Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	416,470	391,654
Recurring basis fair value measurements | Fair Value Measurements Using Level 2 | U.S. government agency securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	16,490	21,649
Recurring basis fair value measurements | Fair Value Measurements Using Level 2 | State, county and municipals
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	147,786	160,460
Recurring basis fair value measurements | Fair Value Measurements Using Level 2 | Mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	171,877	131,644
Recurring basis fair value measurements | Fair Value Measurements Using Level 2 | Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	80,317	77,901
Recurring basis fair value measurements | Fair Value Measurements Using Level 2 | Other investments (equity securities)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments (equity securities)	0	0
Recurring basis fair value measurements | Fair Value Measurements Using Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	2,830	8,490
Recurring basis fair value measurements | Fair Value Measurements Using Level 3 | U.S. government agency securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0	0
Recurring basis fair value measurements | Fair Value Measurements Using Level 3 | State, county and municipals
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0	66
Recurring basis fair value measurements | Fair Value Measurements Using Level 3 | Mortgage-backed securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	0	0
Recurring basis fair value measurements | Fair Value Measurements Using Level 3 | Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Fair Value	2,830	8,424
Recurring basis fair value measurements | Fair Value Measurements Using Level 3 | Other investments (equity securities)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Other investments (equity securities)	$ 0	$ 0