Debt - Preferred Securities (Details) - USD ($)	3 Months Ended	6 Months Ended
	Mar. 31, 2021	Jun. 30, 2020	Dec. 31, 2020
NYM Preferred Trust I
Debt Instrument [Line Items]
Principal value of trust preferred securities	$ 25,000,000		$ 25,000,000
NYM Preferred Trust I | LIBOR
Debt Instrument [Line Items]
Interest rate, basis spread	3.75%	3.75%
NYM Preferred Trust II
Debt Instrument [Line Items]
Principal value of trust preferred securities	$ 20,000,000		$ 20,000,000
NYM Preferred Trust II | LIBOR
Debt Instrument [Line Items]
Interest rate, basis spread	3.95%	3.95%