Quarterly Financial Data (Unaudited) (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Selected quarterly financial data and earnings per share [Abstract]
Revenues	$ 968,096	$ 1,060,340	$ 965,098	$ 952,435	$ 875,666	$ 794,404	$ 830,110	$ 875,905	$ 3,945,969	$ 3,376,085	$ 3,038,737
Earnings from continuing operations	289	7,238	6,521	8,073	7,840	8,355	5,333	5,944	22,121	27,472	22,718
Earnings from continuing operations, Per Share (in dollars per share)	$ 0.06	$ 1.72	$ 1.55	$ 1.91	$ 1.86	$ 1.98	$ 1.26	$ 1.41	$ 5.24	$ 6.51	$ 5.39
Net Earnings	109	7,156	6,330	8,015	7,567	8,263	5,386	6,575	21,610	27,791	22,931
Net Earnings, Per Share (in dollars per share)	$ 0.02	$ 1.70	$ 1.50	$ 1.90	$ 1.79	$ 1.96	$ 1.28	$ 1.56	$ 5.12	$ 6.59	$ 5.44
Dividends	$ 928	$ 927	$ 928	$ 0	$ 2,615	$ 0	$ 0	$ 0	$ 2,783	$ 2,615	$ 2,404
Dividends, Per share (in dollars per share)	$ 0.22	$ 0.22	$ 0.22	$ 0	$ 0.62	$ 0	$ 0	$ 0	$ 0.66	$ 0.62