Short-Term Borrowings - Components and Selected Information (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2015
Short-term borrowings
Short-term borrowings	$ 34,951		$ 216,151
Federal funds purchased
Short-term borrowings
Highest month-end balance		$ 8,000
Average outstanding balance	$ 154	$ 9,245
Weighted-average interest rate paid (as a percent)	0.09%	0.02%
Securities sold under agreements to repurchase
Short-term borrowings
Short-term borrowings	$ 34,951		$ 216,151
Weighted-average interest rate (as a percent)	0.35%	0.05%
Highest month-end balance	$ 235,451	$ 520,740
Average outstanding balance	$ 213,271	$ 424,235
Weighted-average interest rate paid (as a percent)	0.08%	0.03%