Deposits - Interest-bearing or Noninterest-bearing (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Dec. 31, 2017
U.S.:
Interest-bearing	$ 10,672,224	$ 10,800,140
Noninterest-bearing	5,361,179	5,494,803
Foreign:
Interest-bearing	758,231	685,129
Noninterest-bearing	603,904	632,050
Total deposits	$ 17,395,538	$ 17,612,122