Deposits - Maturity Distribution of Time Certificates of Deposits (Details) $ in Thousands	Sep. 30, 2020 USD ($)
Maturity distribution of time certificates of deposit
Three months or less	$ 625,577
Over three through six months	576,928
Over six through twelve months	880,095
One to two years	261,826
Two to three years	128,938
Three to four years	89,186
Four to five years	51,415
Thereafter	855
Total	2,614,820
Under $250,000
Maturity distribution of time certificates of deposit
Three months or less	215,127
Over three through six months	215,480
Over six through twelve months	337,669
One to two years	124,819
Two to three years	86,062
Three to four years	79,862
Four to five years	33,808
Thereafter	199
Total	1,093,026
$250,000 or More
Maturity distribution of time certificates of deposit
Three months or less	410,450
Over three through six months	361,448
Over six through twelve months	542,426
One to two years	137,007
Two to three years	42,876
Three to four years	9,324
Four to five years	17,607
Thereafter	656
Total	$ 1,521,794