Securities - Amortized Cost and Fair Value of Securities by Contractual Maturity (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Held-to-maturity Securities, Debt Maturities, Net Carrying Amount [Abstract]
Held to maturity, amortized cost, total	$ 357,949	$ 416,863
Held-to-maturity Securities, Debt Maturities, Fair Value, Fiscal Year Maturity [Abstract]
Held to maturity, fair value, total	349,895	414,470
Available-for-sale Securities, Debt Maturities, Amortized Cost Basis, Fiscal Year Maturity [Abstract]
Available for sale, amortized cost, total	882,872	953,720
Available-for-sale Securities, Debt Maturities, Fair Value, Fiscal Year Maturity [Abstract]
Available for sale, fair value, total	865,831	949,460
Mortgage-backed securities and collateralized mortgage obligations of US Government Sponsored Entities
Held-to-maturity Securities, Debt Maturities, Net Carrying Amount [Abstract]
Held to maturity, amortized cost, total	304,423
Held-to-maturity Securities, Debt Maturities, Fair Value, Fiscal Year Maturity [Abstract]
Held to maturity, fair value, total	297,099	350,184
Available-for-sale Securities, Debt Maturities, Amortized Cost Basis, Fiscal Year Maturity [Abstract]
Available for sale, amortized cost, total	567,753	560,396
Available-for-sale Securities, Debt Maturities, Fair Value, Fiscal Year Maturity [Abstract]
Available for sale, fair value, total	554,006	553,525
Private mortgage-backed securities and collateralized mortgage obligations
Held-to-maturity Securities, Debt Maturities, Net Carrying Amount [Abstract]
Held to maturity, amortized cost, total	21,526
Held-to-maturity Securities, Debt Maturities, Fair Value, Fiscal Year Maturity [Abstract]
Held to maturity, fair value, total	21,673	23,460
Available-for-sale Securities, Debt Maturities, Amortized Cost Basis, Fiscal Year Maturity [Abstract]
Available for sale, amortized cost, total	55,569	75,152
Available-for-sale Securities, Debt Maturities, Fair Value, Fiscal Year Maturity [Abstract]
Available for sale, fair value, total	55,728	$ 76,021
Collateralized loan obligations
Held-to-maturity Securities, Debt Maturities, Net Carrying Amount [Abstract]
Held to maturity, amortized cost, due in less than one year	0
Held to maturity, amortized cost, due after one year through five years	0
Held to maturity, amortized cost, due after five years through ten years	32,000
Held to maturity, amortized cost, due after ten years	0
Held to maturity, amortized cost, total	32,000
Held-to-maturity Securities, Debt Maturities, Fair Value, Fiscal Year Maturity [Abstract]
Held to maturity, fair value, due in less than one year	0
Held to maturity, fair value, due after one year through five years	0
Held to maturity, fair value, due after five years through ten years	31,123
Held to maturity, fair value, due after ten years
Held to maturity, fair value, total	31,123
Available-for-sale Securities, Debt Maturities, Amortized Cost Basis, Fiscal Year Maturity [Abstract]
Available for sale, amortized cost, due in less than one year	12,190
Available for sale, amortized cost, due after one year through five years	88,402
Available for sale, amortized cost, due after five years through ten years	155,493
Available for sale, amortized cost, due after ten years	3,465
Available for sale, amortized cost, total	259,550
Available-for-sale Securities, Debt Maturities, Fair Value, Fiscal Year Maturity [Abstract]
Available for sale, fair value, due in less than one year	12,131
Available for sale, fair value, due after one year through five years	87,808
Available for sale, fair value, due after five years through ten years	152,707
Available for sale, fair value, due after ten years	3,451
Available for sale, fair value, total	$ 256,097