Related Party Transactions (Narrative) (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Related Party Transaction [Line Items]
Rent expense	$ 17,200,000	$ 12,900,000	$ 8,400,000
Net charter income	969,703,000	902,960,000	880,010,000
Percentage Under Tax Receivable Agreement	85.00%
Tax Receivable Agreement Liability	58,700,000
Tax Receivable Agreement Liability Discount Rate	5.47%
Affiliated Entity
Related Party Transaction [Line Items]
Rent expense	7,400,000	5,800,000	3,400,000
Western Airlines
Related Party Transaction [Line Items]
Net charter income	$ 1,500,000	$ 1,000,000	$ 1,000,000