Commitments and Contingencies - Colombia-Related Matters - Insurance Recovery (Details) (USD $)	3 Months Ended		12 Months Ended	1 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2008 insurer	Jun. 30, 2013 insurer	Dec. 31, 2009 insurer
Gain Contingencies [Line Items]
Interest income	$ 664,000	$ 664,000
Colombia | Insurance recovery coverage suit
Gain Contingencies [Line Items]
Initial number of primary general liability insurers involved in coverage suit		1	3
Number of primary insurers with which the company reached settlement agreements					3
Percent of defense costs in the ATA and ATS lawsuits to be paid by primary insurers					40.00%
Expense reimbursement received to date which is deferred in Other liabilities	12,000,000
Interest income	$ 1,000,000
Colombia | Two insurers who had been placed in liquidation
Gain Contingencies [Line Items]
Initial number of primary general liability insurers involved in coverage suit				2
Percent of defense costs in the ATA and ATS lawsuits to be paid by primary insurers					1.00%
Colombia | Defendant seeking a declaratory judgment relieving coverage obligation
Gain Contingencies [Line Items]
Initial number of primary general liability insurers involved in coverage suit	1
Percent of defense costs in the ATA and ATS lawsuits to be paid by primary insurers					40.00%