Summary of Significant Accounting Policies (Additional Information 2) (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2016 USD ($) segment	Jun. 30, 2015	Dec. 31, 2015 USD ($)
Summary Of Significant Accounting Policies [Line Items]
Capital lease obligations	$ 21,700		$ 26,900
Lease financing obligations	21,700		22,800
Net book value of assets associated with leases	$ 45,500		51,000
Number of operating segments | segment	1
Number of reportable segments | segment	1
Financial assets	$ 0		0
Financial liability	$ 0		0
Effective tax rate	38.20%	(23.40%)
Accounts Receivable [Member]
Summary Of Significant Accounting Policies [Line Items]
Aggregate allowance for doubtful accounts	$ 4,100		$ 5,100
Customer One [Member] | Rental Revenue [Member] | Maximum [Member]
Summary Of Significant Accounting Policies [Line Items]
Percentage of total revenue	11.60%
Two Customers [Member] | Accounts Receivable [Member] | Minimum [Member]
Summary Of Significant Accounting Policies [Line Items]
Percentage of total accounts receivable	10.00%
Other Customers [Member] | Rental Revenue [Member] | Maximum [Member]
Summary Of Significant Accounting Policies [Line Items]
Percentage of total revenue	4.00%
Six Customers [Member] | Accounts Receivable [Member] | Minimum [Member]
Summary Of Significant Accounting Policies [Line Items]
Percentage of total accounts receivable	5.00%
Six Customers [Member] | Accounts Receivable [Member] | Maximum [Member]
Summary Of Significant Accounting Policies [Line Items]
Percentage of total accounts receivable	55.00%