Consolidated Balance Sheets Parenthetical disclosures - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Available-for-sale Securities, Debt Maturities, Amortized Cost Basis	$ 6,661,711	$ 6,379,919
Available-for-sale Equity Securities, Amortized Cost Basis	$ 130,479	$ 116,336
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 stock, shares outstanding	24,893,955	24,808,176
Common Class A
Common stock, shares authorized	88,500,000	88,500,000
Common Stock, Shares, Issued	24,882,542	24,796,763
Common stock, shares outstanding	24,882,542	24,796,763
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