Schedule II - Condensed Financial Information of Registrant (Parent Company Only) (Balance Sheet) (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
ASSETS
Cash and cash equivalents	$ 79,632	$ 114,446	$ 130,985	$ 141,666
Investment in subsidiaries	1,702	1,702
Deferred federal income taxes	1,365	3,360
Federal income tax recoverable	3,951	1,779
Other assets	13,801	10,192
Total assets	1,162,460	1,075,547
LIABILITIES AND STOCKHOLDERS' EQUITY
Revolving credit facility payable	30,000	30,000
Subordinated debt securities (less unamortized debt issuance cost of $1,001 in 2016 and $1,053 in 2015)	55,701	55,649
Accounts payable and other accrued expenses	25,296	23,253
Total liabilities	896,724	813,521
Stockholders' equity:
Common stock, $.18 par value, authorized 33,333,333 shares; issued 20,872,831 shares in 2016 and 2015	3,757	3,757
Capital in excess of par value	123,166	123,480
Retained earnings	148,027	141,501
Accumulated other comprehensive income	10,371	7,418
Treasury stock (2,260,849 shares in 2016 and 1,775,512 in 2015), at cost	(19,585)	(14,130)
Total stockholders equity	265,736	262,026	252,037	238,118
Total liabilities and stockholders' equity	1,162,460	1,075,547
Parent Company [Member]
ASSETS
Cash and cash equivalents	9,034	8,014	$ 11,839	$ 8,063
Investment in subsidiaries	363,078	361,769
Deferred federal income taxes	333	942
Federal income tax recoverable	2,756
Other assets	3,878	3,435
Total assets	379,079	374,160
LIABILITIES AND STOCKHOLDERS' EQUITY
Revolving credit facility payable	30,000	30,000
Subordinated debt securities (less unamortized debt issuance cost of $1,001 in 2016 and $1,053 in 2015)	55,701	55,649
Current federal income tax payable		72
Accounts payable and other accrued expenses	27,642	26,413
Total liabilities	113,343	112,134
Stockholders' equity:
Common stock, $.18 par value, authorized 33,333,333 shares; issued 20,872,831 shares in 2016 and 2015	3,757	3,757
Capital in excess of par value	123,166	123,480
Retained earnings	148,027	141,501
Accumulated other comprehensive income	10,371	7,418
Treasury stock (2,260,849 shares in 2016 and 1,775,512 in 2015), at cost	(19,585)	(14,130)
Total stockholders equity	265,736	262,026
Total liabilities and stockholders' equity	$ 379,079	$ 374,160