Segments (Reconciliation of reportable segment adjusted EBITDA) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Segment Reporting Information [Line Items]
Reportable segment Adjusted EBITDA	$ 84,471	$ 62,139	$ 159,268	$ 120,788
Less depreciation and amortization expense	(43,786)	(34,396)	(86,138)	(68,395)
Less share-based compensation expense			(3,971)	(2,906)
Other	1,049	(53)	1,146	(53)
Operating income	38,414	25,695	68,679	48,755
Less other expense	(19,219)	(17,474)	(37,527)	(34,378)
Income before income tax expense	19,195	8,221	31,152	14,377
Segment Reconciling Items [Member]
Segment Reporting Information [Line Items]
Reportable segment Adjusted EBITDA	84,471	62,139	159,268	120,788
Less depreciation and amortization expense	(43,786)	(34,396)	(86,138)	(68,395)
Less share-based compensation expense	(2,193)	(1,647)	(3,971)	(2,906)
Less accretion expense	(301)	(155)	(602)	(282)
Other	223	(246)	122	(450)
Operating income	38,414	25,695	68,679	48,755
Less other expense	(19,219)	(17,474)	(37,527)	(34,378)
Income before income tax expense	$ 19,195	$ 8,221	$ 31,152	$ 14,377