Related-Party Transactions (Details) (Zions Bancorporation, USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2014 aircraft	Dec. 31, 2013
Related Party Transactions
Cash balance with related party		90.6	$ 81.8
Minimum
Related Party Transactions
Refinancing term	3 years
Maximum
Related Party Transactions
Refinancing term	4 years
CRJ 200
Related Party Transactions
Equity participation in leveraged leases on number of aircraft		2
Number of refinanced aircraft	6
CRJ 700
Related Party Transactions
Equity participation in leveraged leases on number of aircraft		2
Number of refinanced aircraft	2
Brasilia turboprop aircraft
Related Party Transactions
Equity participation in leveraged leases on number of aircraft		4