Consolidated Balance Sheets (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Investments:
Securities held to maturity-fair value	$ 7,175,443	$ 6,656,144
Securities available for sale-amortized cost	2,590,074	2,535,264
Mortgage loans-allowance for possible losses	$ 650	$ 650
Common Class A [Member]
STOCKHOLDERS’ EQUITY:
Common stock, par value	$ 1	$ 1
Common Stock, shares authorized	7,500,000	7,500,000
Common Stock, shares issued	3,436,166	3,434,765
Common Stock, shares outstanding	3,436,166	3,434,765
Common Class B [Member]
STOCKHOLDERS’ EQUITY:
Common stock, par value	$ 1	$ 1
Common Stock, shares authorized	200,000	200,000
Common Stock, shares issued	200,000	200,000
Common Stock, shares outstanding	200,000	200,000