Supplemental Selected Quarterly Financial Information (Schedule Of Supplemental Selected Quarterly Financial Information) (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
Supplemental Selected Quarterly Financial Information [Abstract]
Total revenues	$ 241,945		$ 228,819		$ 207,984		$ 197,738		$ 198,360		$ 199,029		$ 192,020		$ 191,040		$ 876,486		$ 780,449		$ 624,576
Gross profit	78,326	[1]	68,550	[1]	70,274	[1]	64,049	[1]	64,510	[2]	62,300	[2]	58,920	[2]	58,632	[2]	281,199	[1]	244,362	[2]	204,461
Net income (loss)	5,716		(8,982)		14,765		9,148		10,934		12,706		9,579		10,043		20,647		43,262		70,146
Net income (loss) attributable to controlling interests and available to common stockholders	7,467		(8,408)		15,327		9,430		11,201		12,897		9,664		9,829		23,816		43,591		70,233
Basic net income (loss) per common share	$ 0.16		$ (0.19)		$ 0.34		$ 0.21		$ 0.25		$ 0.29		$ 0.22		$ 0.22		$ 0.52		$ 0.97		$ 1.60
Diluted net income (loss) per common share	$ 0.16		$ (0.19)		$ 0.33		$ 0.21		$ 0.25		$ 0.28		$ 0.21		$ 0.22		$ 0.52		$ 0.96		$ 1.58
Depreciation, accretion, and amortization expense	$ 24,500		$ 22,800		$ 19,900		$ 20,000		$ 20,000		$ 19,100		$ 18,200		$ 17,400		$ 87,177		$ 74,740		$ 59,278

[1] Excludes $20.0 million, $19.9 million, $22.8 million and $24.5 million of depreciation, accretion, and amortization for the quarters ended March 31, June 30, September 30, and December 31, respectively.

[2] Excludes $17.4 million, $18.2 million, $19.1 million and $20.0 million of depreciation, accretion, and amortization for the quarters ended March 31, June 30, September 30, and December 31, respectively.