Derivative Financial Instruments (Net gains or losses) (Details 3) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Derivative Instruments, Gain (Loss)
Net gains (losses) recognized in the statements of income	$ 2,296	$ 2,049
Interest Rate Lock Commitments | Mortgage Banking Income
Derivative Instruments, Gain (Loss)
Net gains (losses) recognized in the statements of income	530	1,267
Forward Commitments | Mortgage Banking Income
Derivative Instruments, Gain (Loss)
Net gains (losses) recognized in the statements of income	684	(424)
Interest Rate Swap Agreements | Other Noninterest Income
Derivative Instruments, Gain (Loss)
Net gains (losses) recognized in the statements of income	118	156
Foreign Exchange Contracts | Other Noninterest Income
Derivative Instruments, Gain (Loss)
Net gains (losses) recognized in the statements of income	$ 964	$ 1,050