Commitments and Contingencies - Variable Interests (Details)	12 Months Ended
	Dec. 31, 2018 USD ($) investment tranch	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2034 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)
Variable Interest Entity [Line Items]
Number of equity investments in LIHTCs | investment	2
Investments in unconsolidated LIHTCs	$ 50,900,000	$ 54,000,000
Tax benefits	2,400,000	2,900,000	$ 640,000
Commitments	31,500,000	39,800,000
Impairment losses on LIHTC investments	0	0	0
Carrying value of NMTC	25,700,000	25,800,000
Investment income	708,000	$ 735,000	$ 740,000
Subsidiaries | Investment Tax Credit Carryforward
Variable Interest Entity [Line Items]
Qualified Equity Investments	$ 25,000,000
Number of tranches | tranch	3
Percentage of tranche required to fund to claim the entire tax credit	85.00%
Subsidiaries | Investment Tax Credit Carryforward | 2020
Variable Interest Entity [Line Items]
Gross tax credits related to the Company's CDEs	$ 9,800,000
Forecast
Variable Interest Entity [Line Items]
Qualified Affordable Housing Project Investments, future commitment				$ 4,500,000	$ 523,000	$ 26,400,000