Deposits - Maturity Distribution of Time Certificates of Deposits (Details) $ in Thousands	Sep. 30, 2016 USD ($)
Maturity distribution of time certificates of deposits
Three months or less	$ 1,789,175
Over three through six months	979,413
Over six through twelve months	617,819
One to two years	149,372
Two to three years	190,157
Three to four years	136,508
Four to five years	142,592
Thereafter	107
Total	4,005,143
Under $250,000
Maturity distribution of time certificates of deposits
Three months or less	250,817
Over three through six months	162,312
Over six through twelve months	377,824
One to two years	82,410
Two to three years	141,117
Three to four years	98,047
Four to five years	102,580
Thereafter	107
Total	1,215,214
$250,000 or More
Maturity distribution of time certificates of deposits
Three months or less	1,538,358
Over three through six months	817,101
Over six through twelve months	239,995
One to two years	66,962
Two to three years	49,040
Three to four years	38,461
Four to five years	40,012
Total	$ 2,789,929