Earnings Per Share (Details)	3 Months Ended								12 Months Ended
	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2010	Sep. 30, 2010	Jun. 30, 2010	Mar. 31, 2010	Dec. 31, 2011		Dec. 31, 2010		Dec. 31, 2009
Basic computation	36,271,000	36,262,000	36,258,000	36,242,000	36,217,000	36,196,000	36,179,000	36,169,000	36,258,463		36,190,373		36,091,362
Restricted stock and performance share awards (1)									288,746	[1]	28,748	[1]
Diluted computation									36,547,209		36,219,121
Performance Share Awards [Member]
Antidilutive securities excluded from computation of earnings per share, amount											107,516

[1] Performance share awards are included in diluted weighted average number of shares outstanding based upon what would be issued if the end of the most recent reporting period was the end of the term of the award. The dilutive share calculation for 2010 excludes 107,516 shares under outstanding performance share awards because the inclusion of these awards would have been antidilutive under the treasury stock method.