Borrowings - Long Term Borrowings (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Line of Credit Facility [Line Items]
Long-term borrowings	$ 2,167,979	$ 579,101
Weighted Average Interest Rate	2.15%	2.10%
Average Balance	$ 1,236,045	$ 253,759
Floating rate borrowings
Line of Credit Facility [Line Items]
Long-term borrowings	$ 1,175,819	$ 337,098
Weighted Average Interest Rate	1.71%	1.38%
Average Balance	$ 687,580	$ 151,373
Fixed rate borrowings
Line of Credit Facility [Line Items]
Long-term borrowings	$ 992,160	$ 242,003
Weighted Average Interest Rate	2.68%	3.11%
Average Balance	$ 548,465	$ 102,386