Derivative Financial Instruments (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Junior subordinated debentures	$ 35,570		$ 35,570		$ 44,384
Notional amount	1,366,244		1,366,244		885,469
Short-term Debt, Total	1,021,500		1,021,500		541,500
Amount reclassified from accumulated other comprehensive loss to interest expense	600	$ 600	800	$ 800
Amount to be reclassified from the accumulated comprehensive income (loss) into earnings			1,600
Not Designated as Hedging Instrument [Member]
Notional amount	23,700		23,700		23,700
Designated as Hedging Instrument [Member]
Notional amount	321,100		321,100		326,000
Designated as Hedging Instrument [Member] | Cash Flow Hedging [Member]
Notional amount	1,021,500		1,021,500		541,500
Interest Rate Swap [Member]
Notional amount	326,700		326,700		326,000
Interest Rate Swap [Member] | Not Designated as Hedging Instrument [Member]
Notional amount	20,842		20,842		18,000
Interest Rate Swap [Member] | Designated as Hedging Instrument [Member] | Cash Flow Hedging [Member]
Notional amount	1,021,500		1,021,500		541,500
Floating Rate Junior Subordinated Debentures [Member]
Amount of hedged item	18,000		18,000		18,000
Junior subordinated debentures	$ 61,900		$ 61,900		$ 61,900