Selected Quarterly Financial Data - (Unaudited) (Tables)

12 Months Ended

Dec. 31, 2012

Quarterly Financial Information Disclosure [Abstract]

Schedule of Quarterly Financial Data - (Unaudited)

	First   Quarter		Second   Quarter		Third   Quarter		Fourth   Quarter		2012
	(In thousands, except per share data)
Revenues	$	129,169	$	173,621	$	210,413	$	178,306	$	691,509
Operating income	$	31,065	$	51,590	$	65,253	$	45,234	$	193,142
Income before income taxes	$	30,233	$	47,939	$	55,668	$	35,328	$	169,168
Net income	$	19,997	$	31,862	$	44,377	$	24,451	$	120,687
Per basic share:
Net income	$	0.34	$	0.55	$	0.77	$	0.42	$	2.08
Per diluted share:
Net income	$	0.34	$	0.55	$	0.76	$	0.42	$	2.07
	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