Commitments and Contingencies - Colombia-Related - Tort Lawsuits (Details) (USD $)	3 Months Ended		9 Months Ended		12 Months Ended	1 Months Ended		46 Months Ended	9 Months Ended				37 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2007 Colombia ATS lawsuits count	Nov. 30, 2012 Colombia ATA lawsuits lawsuit	Feb. 28, 2010 Colombia ATA lawsuits lawsuit	Mar. 31, 2011 Colombia Pending litigation ATS lawsuits lawsuit	Sep. 30, 2014 Colombia Pending litigation ATS lawsuits Minimum plaintiff	Sep. 30, 2014 Colombia Pending litigation Unspecified compensatory and punitive damages and attorney's fees and costs lawsuit	Sep. 30, 2014 Colombia Pending litigation Treble damages and disgorgement of profits without explanation lawsuit	Sep. 30, 2014 Colombia Pending litigation Specific demand	Mar. 31, 2011 Colombia Pending litigation ATA lawsuits lawsuit
Loss Contingencies [Line Items]
Interest income	$ 600,000	$ 690,000	$ 1,905,000	$ 2,197,000
Number of new claims filed								9					4
Minimum number of alleged victims									6,000
Number of lawsuits plead or dismissed after the parties reached a confidential settlement agreement					1	1
Number of pending lawsuits										8	1
Specific demand for compensatory damages												10,000,000
Specific demand for punitive damages												$ 10,000,000
Number of lawsuits for which the motion to dismiss was granted in part and denied in part							1