Deposits - Deposits (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Deposits
Non-interest bearing checking	$ 7,948,637	$ 3,921,710
Interest bearing checking	5,966,178	2,459,617
Total checking	13,914,815	6,381,327
Savings	8,521,093	6,122,257
Money market	4,576,999	1,609,422
Certificates of deposit	7,455,556	4,790,680
Total deposits	$ 34,468,463	$ 18,903,686
Year-to-Date Weighted-average Rate
Interest bearing checking	0.36%	0.03%
Total checking	0.15%	0.01%
Savings	0.72%	0.36%
Money market	1.38%	0.75%
Certificates of deposit	2.01%	1.54%
Total deposits	0.88%	0.59%