Segment and Geographic Area Information Operating Revenues by Geographic Area (Details) (USD $) In Thousands, 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
Segment Reporting Information [Line Items]
Operating revenues	$ 391,674	$ 401,388	$ 400,741	$ 375,208	$ 227,316	$ 222,745	$ 217,419	$ 207,436	$ 1,569,011	$ 874,916	$ 829,096
Percent of total operating revenues									100.00%	100.00%	100.00%
United States [Member]
Segment Reporting Information [Line Items]
Operating revenues									1,083,773	489,157	478,511
Percent of total operating revenues									69.10%	55.90%	57.70%
Australian Operations [Member]
Segment Reporting Information [Line Items]
Operating revenues									325,164	289,023	271,475
Percent of total operating revenues									20.70%	33.00%	32.70%
Canada [Member]
Segment Reporting Information [Line Items]
Operating revenues									145,399	81,948	64,155
Percent of total operating revenues									9.30%	9.40%	7.80%
Europe [Member]
Segment Reporting Information [Line Items]
Operating revenues									14,675	14,788	14,955
Percent of total operating revenues									0.90%	1.70%	1.80%
Total Non-United States
Segment Reporting Information [Line Items]
Operating revenues									$ 485,238	$ 385,759	$ 350,585
Percent of total operating revenues									30.90%	44.10%	42.30%