Quarterly Financial Information (Unaudited) (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Revenues	$ 54,070	$ 52,182	$ 49,602	$ 46,905	$ 52,458	$ 48,333	$ 48,296	$ 45,069	$ 202,759	$ 194,156	$ 190,324
Benefits and expenses	54,511	48,137	49,263	44,812	50,779	45,551	43,918	42,578	196,723	182,826	171,935
Federal income tax expense	(144)	1,134	(64)	581	(119)	729	1,369	869	1,507	2,848	3,685
Net income	(297)	2,911	403	1,512	1,798	2,053	3,009	1,622	4,529	8,482	14,704
Common Class A [Member]
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest	$ (297)	$ 2,911	$ 403	$ 1,512	$ 1,798	$ 2,053	$ 3,009	$ 1,622
Basic earnings per share	$ (0.01)	$ 0.06	$ 0.01	$ 0.03	$ 0.04	$ 0.04	$ 0.06	$ 0.03		$ 0.17	$ 0.30
Diluted earnings per share	$ (0.01)	$ 0.06	$ 0.01	$ 0.03	$ 0.04	$ 0.04	$ 0.04	$ 0.03		$ 0.17	$ 0.30
Common Class B [Member]
Basic earnings per share	$ 0.00	$ 0.03	$ 0.00	$ 0.02	$ 0.02	$ 0.02	$ 0.03	$ 0.02
Diluted earnings per share	$ 0.00	$ 0.03	$ 0.00	$ 0.02	$ 0.02	$ 0.02	$ 0.03	$ 0.01