Debt Covenant Ratios (Details) - Credit Agreement	Sep. 30, 2016	Dec. 31, 2015
Debt Instrument [Line Items]
Net total lease adjusted leverage ratio	5.7	5.6
Net secured debt lease adjusted leverage ratio	2.6	2.6
Bond leverage ratio, per indentures	5.4	5.5
Fixed charge coverage ratio	2.5	2.4
Maximum
Debt Instrument [Line Items]
Net total lease adjusted leverage ratio	6.5
Net secured debt lease adjusted leverage ratio	4.0
Bond leverage ratio, per indentures	6.5
Minimum
Debt Instrument [Line Items]
Fixed charge coverage ratio	1.5