Business Segments (Summarized Geographic Information Related to the Company's Operating Revenues) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Segment revenues	$ 768,374	$ 713,335	$ 697,734	$ 696,517	$ 653,199	$ 630,403	$ 597,235	$ 562,695	$ 2,875,960	$ 2,443,532	$ 1,985,335
UNITED STATES
Segment revenues									2,013,159	1,801,607	1,614,436
International [Member]
Segment revenues									862,801	641,925	370,899
International [Member] | BRAZIL
Segment revenues									198,068	177,526	104,922
International [Member] | CHILE
Segment revenues									22,114	7,380	735
International [Member] | COLOMBIA
Segment revenues									48,424	13,690	1,553
International [Member] | GERMANY
Segment revenues									4,030	0	0
International [Member] | GHANA
Segment revenues									81,818	41,464	0
International [Member] | INDIA
Segment revenues									181,863	170,680	98,799
International [Member] | MEXICO
Segment revenues									217,473	183,175	164,039
International [Member] | PERU
Segment revenues									5,310	4,546	851
International [Member] | SOUTH AFRICA
Segment revenues									80,202	43,464	0
International [Member] | UGANDA
Segment revenues									$ 23,499	$ 0	$ 0