Borrowings - Corporate Revolving Line of Credit (Details) - Revolving credit agreement - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Short-term debt
Interest expense	$ 1,921	$ 1,913	$ 2,368
Unused amount		150,000	150,000
Cash pledged to secure corporate revolver		$ 52,599	$ 108,174