Deposits - Interest-bearing or Noninterest-bearing (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Dec. 31, 2017
U.S.:
Interest-bearing	$ 10,576,408	$ 10,800,140
Noninterest-bearing	5,419,275	5,494,803
Foreign:
Interest-bearing	735,880	685,129
Noninterest-bearing	630,859	632,050
Total deposits	$ 17,362,422	$ 17,612,122