Borrowings - Short-Term Credit Facilities (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Short-Term Credit Facilities
Interest expense	$ 24,593	$ 7,393	$ 40,141	$ 21,569
Short-Term Credit Facilities
Short-Term Credit Facilities
Weighted average interest rate	3.56%		3.56%		3.12%
Interest expense	$ 1,400	$ 1,800	$ 4,800	$ 5,000