Commitments and Contingencies - Commitments and Letters of Credit (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2017	Dec. 31, 2016
Other Commitments [Line Items]
Commitments and letters of credit	$ 1,498,011	$ 1,594,230
Commitments to Extend Credit
Other Commitments [Line Items]
Commitments and letters of credit	1,415,003	1,509,696
Standby Letters of Credit
Other Commitments [Line Items]
Commitments and letters of credit	$ 83,008	$ 84,534