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Basis of Presentation - Schedule of Reclassification of Debt Securities (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Jan. 01, 2019	Dec. 31, 2018
Schedule of Available-for-sale Securities [Line Items]
Held to maturity, amortized cost	$ 882,557		$ 882,872
Available for sale, fair value	877,549		865,831
Private mortgage-backed securities and collateralized mortgage obligations
Schedule of Available-for-sale Securities [Line Items]
Held to maturity, amortized cost	67,206		55,569
Available for sale, fair value	67,935		55,728
Collateralized loan obligations
Schedule of Available-for-sale Securities [Line Items]
Held to maturity, amortized cost	243,546		212,807
Available for sale, fair value	$ 241,739		$ 209,366
Accounting Standards Update 2017-12
Schedule of Available-for-sale Securities [Line Items]
Held to maturity, amortized cost		$ 53,526
Net Unrealized Gain (Loss) Reflected in OCI		(730)
Available for sale, fair value		52,796
Accounting Standards Update 2017-12 \| Private mortgage-backed securities and collateralized mortgage obligations
Schedule of Available-for-sale Securities [Line Items]
Held to maturity, amortized cost		21,526
Net Unrealized Gain (Loss) Reflected in OCI		147
Available for sale, fair value		21,673
Accounting Standards Update 2017-12 \| Collateralized loan obligations
Schedule of Available-for-sale Securities [Line Items]
Held to maturity, amortized cost		32,000
Net Unrealized Gain (Loss) Reflected in OCI		(877)
Available for sale, fair value		$ 31,123