Deposits - Maturity Distribution of Time Certificates of Deposits (Details) $ in Thousands	Mar. 31, 2017 USD ($)
Maturity distribution of time certificates of deposit
Three months or less	$ 1,755,022
Over three through six months	855,537
Over six through twelve months	654,076
2018	225,086
2019	167,679
2020	128,754
2020	131,155
Thereafter	17
Total	3,917,326
Under $250,000
Maturity distribution of time certificates of deposit
Three months or less	210,516
Over three through six months	226,432
Over six through twelve months	332,090
2018	110,471
2019	128,127
2020	87,470
2020	93,886
Thereafter	17
Total	1,189,009
$250,000 or More
Maturity distribution of time certificates of deposit
Three months or less	1,544,506
Over three through six months	629,105
Over six through twelve months	321,986
2018	114,615
2019	39,552
2020	41,284
2020	37,269
Total	$ 2,728,317