Selected Quarterly Financial Data - (Unaudtited) (Tables)

12 Months Ended

Dec. 31, 2011

Quarterly Financial Information Disclosure [Abstract]

Schedule of Quarterly Financial Information

	First   Quarter		Second   Quarter		Third   Quarter		Fourth   Quarter		2011
	(In thousands, except per share data)
Revenues	$	115,281	$	165,301	$	192,321	$	165,890	$	638,793
Operating income	$	25,679	$	45,122	$	62,400	$	38,662	$	171,863
Income before income taxes	$	21,923	$	42,114	$	56,966	$	37,054	$	158,057
Net income	$	15,730	$	27,578	$	42,302	$	24,786	$	110,396
Per basic share:
Net income	$	0.26	$	0.46	$	0.71	$	0.42	$	1.86
Per diluted share:
Net income	$	0.26	$	0.46	$	0.71	$	0.42	$	1.85
	First   Quarter		Second   Quarter		Third   Quarter		Fourth   Quarter		2010
	(In thousands, except per share data)
Revenues	$	107,421	$	149,848	$	183,801	$	155,006	$	596,076
Operating income	$	23,837	$	43,607	$	54,877	$	38,441	$	160,762
Income before income taxes	$	24,646	$	42,024	$	55,026	$	36,515	$	158,211
Net income	$	15,793	$	27,011	$	40,494	$	24,143	$	107,441
Per basic share:
Net income	$	0.27	$	0.45	$	0.68	$	0.41	$	1.80
Per diluted share:
Net income	$	0.26	$	0.45	$	0.68	$	0.40	$	1.80