Fair Value Measurements - Assets and Liabilities Measured on Recurring Basis (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total securities available-for-sale	$ 932,070	$ 710,570
U.S. government and agency obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total securities available-for-sale	53,562	39,644
Mortgage-backed securities and collateralized mortgage obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total securities available-for-sale	815,532	606,612
Municipal obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total securities available-for-sale	1,586	1,957
Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total securities available-for-sale	53,567	54,514
Trust preferred securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total securities available-for-sale	4,630	4,656
Equity securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total securities available-for-sale	3,193	3,187
Quoted prices in active markets for identical assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total securities available-for-sale		42,831
Derivative assets	0	0
Derivative liabilities		0
Significant other observable inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total securities available-for-sale		667,739
Derivative assets	965	490
Derivative liabilities		203
Significant unobservable inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total securities available-for-sale	0	0
Derivative assets	0	0
Derivative liabilities		0
Measured on recurring basis
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total securities available-for-sale	932,070	710,570
Derivative assets	965	490
Assets	933,035	711,060
Derivative liabilities		203
Measured on recurring basis | U.S. government and agency obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total securities available-for-sale	53,562	39,644
Measured on recurring basis | Mortgage-backed securities and collateralized mortgage obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total securities available-for-sale	815,532	606,612
Measured on recurring basis | Municipal obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total securities available-for-sale	1,586	1,957
Measured on recurring basis | Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total securities available-for-sale	53,567	54,514
Measured on recurring basis | Trust preferred securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total securities available-for-sale	4,630	4,656
Measured on recurring basis | Equity securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total securities available-for-sale	3,193	3,187
Measured on recurring basis | Quoted prices in active markets for identical assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total securities available-for-sale	56,755	42,831
Derivative assets	0	0
Assets	56,755	42,831
Derivative liabilities		0
Measured on recurring basis | Quoted prices in active markets for identical assets (Level 1) | U.S. government and agency obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total securities available-for-sale	53,562	39,644
Measured on recurring basis | Quoted prices in active markets for identical assets (Level 1) | Mortgage-backed securities and collateralized mortgage obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total securities available-for-sale	0	0
Measured on recurring basis | Quoted prices in active markets for identical assets (Level 1) | Municipal obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total securities available-for-sale	0	0
Measured on recurring basis | Quoted prices in active markets for identical assets (Level 1) | Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total securities available-for-sale	0	0
Measured on recurring basis | Quoted prices in active markets for identical assets (Level 1) | Trust preferred securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total securities available-for-sale	0	0
Measured on recurring basis | Quoted prices in active markets for identical assets (Level 1) | Equity securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total securities available-for-sale	3,193	3,187
Measured on recurring basis | Significant other observable inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total securities available-for-sale	875,315	667,739
Derivative assets	965	490
Assets	876,280	668,229
Derivative liabilities		203
Measured on recurring basis | Significant other observable inputs (Level 2) | U.S. government and agency obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total securities available-for-sale	0	0
Measured on recurring basis | Significant other observable inputs (Level 2) | Mortgage-backed securities and collateralized mortgage obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total securities available-for-sale	815,532	606,612
Measured on recurring basis | Significant other observable inputs (Level 2) | Municipal obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total securities available-for-sale	1,586	1,957
Measured on recurring basis | Significant other observable inputs (Level 2) | Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total securities available-for-sale	53,567	54,514
Measured on recurring basis | Significant other observable inputs (Level 2) | Trust preferred securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total securities available-for-sale	4,630	4,656
Measured on recurring basis | Significant other observable inputs (Level 2) | Equity securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total securities available-for-sale	0	0
Measured on recurring basis | Significant unobservable inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total securities available-for-sale	0	0
Derivative assets	0	0
Assets	0	0
Derivative liabilities		0
Measured on recurring basis | Significant unobservable inputs (Level 3) | U.S. government and agency obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total securities available-for-sale	0	0
Measured on recurring basis | Significant unobservable inputs (Level 3) | Mortgage-backed securities and collateralized mortgage obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total securities available-for-sale	0	0
Measured on recurring basis | Significant unobservable inputs (Level 3) | Municipal obligations
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total securities available-for-sale	0	0
Measured on recurring basis | Significant unobservable inputs (Level 3) | Corporate debt securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total securities available-for-sale	0	0
Measured on recurring basis | Significant unobservable inputs (Level 3) | Trust preferred securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total securities available-for-sale	0	0
Measured on recurring basis | Significant unobservable inputs (Level 3) | Equity securities
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total securities available-for-sale	$ 0	$ 0