Borrowings - Summary of Information Pertaining to Borrowings (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Long Term And Short Term Debt [Line Items]
Short-term borrowings	$ 724,923	$ 710,832
Long-term borrowings	58,530	60,332
Total Borrowings	$ 783,453	$ 771,164
Short-term borrowings, Weighted Average Rate	1.25%	0.70%
Long-term borrowings, Weighted Average Rate	3.57%	3.30%
Total Borrowings, Weighted Average Rate	1.42%	0.90%
Securities Sold under Repurchase Agreements
Long Term And Short Term Debt [Line Items]
Short-term borrowings	$ 39,923	$ 50,832
Short-term borrowings, Weighted Average Rate	0.16%	0.01%
Short-Term Borrowings
Long Term And Short Term Debt [Line Items]
Short-term borrowings		$ 660,000
Short-term borrowings, Weighted Average Rate	1.31%	0.76%
Other Long-Term Borrowings
Long Term And Short Term Debt [Line Items]
Long-term borrowings		$ 14,713
Long-term borrowings, Weighted Average Rate	2.97%	2.91%
Junior Subordinated Debt Securities
Long Term And Short Term Debt [Line Items]
Long-term borrowings		$ 45,619
Long-term borrowings, Weighted Average Rate	3.74%	3.42%