Bank Deposits (Scheduled Maturities of Certificates of Deposit) (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Deposits Liabilities Balance Sheet Reported Amounts [Abstract]
Within one year	$ 4,974	$ 4,858
One to three years	480	623
Three to five years	81	140
Certificates of deposit, less than $100,000	5,535	5,621
Within one year	1,002,302	1,535,784
One to three years	142,802	195,159
Three to five years	23,747	26,772
Certificates of deposit, $100,000 and greater	1,168,851	1,757,715
Total certificates of deposit	$ 1,174,386	$ 1,763,336