Consolidated Balance Sheet Parenthetical disclosure - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Available-for-sale Securities, Debt Maturities, Amortized Cost Basis	$ 6,909,984	$ 6,856,277
Equity Securities, Cost	$ 106,021	$ 93,564
Common Stock, Shares, Outstanding	24,659,885	24,718,815
Preferred Stock
Preferred Stock, Shares Authorized	10,000,000	10,000,000
Preferred Stock, Shares Issued	5,000,000	5,000,000
Preferred Stock, Shares Outstanding	5,000,000	5,000,000
Common Class A
Common Stock, Shares Authorized	88,500,000	88,500,000
Common Stock, Shares, Issued	24,648,472	24,707,402
Common Stock, Shares, Outstanding	24,648,472	24,707,402
Common Class B
Common Stock, Shares Authorized	1,500,000	1,500,000
Common Stock, Shares, Issued	11,413	11,413
Common Stock, Shares, Outstanding	11,413	11,413