Deposits - Interest-bearing or Noninterest-bearing (Details) - USD ($) $ in Thousands	Sep. 30, 2018	Dec. 31, 2017
U.S.:
Interest-bearing	$ 10,131,252	$ 10,800,140
Noninterest-bearing	5,200,151	5,494,803
Foreign:
Interest-bearing	750,666	685,129
Noninterest-bearing	607,204	632,050
Total deposits	$ 16,689,273	$ 17,612,122