Deposits - Categorized by Interest-bearing or Noninterest-bearing (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
U.S.:
Interest-bearing	$ 10,982,814	$ 10,129,958
Noninterest-bearing	5,252,249	5,399,212
Foreign:
Interest-bearing	705,035	671,957
Noninterest-bearing	655,385	593,405
Total deposits	$ 17,595,483	$ 16,794,532