Lease Commitments (Details) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Operating Leased Assets [Line Items]
Reduction in rent income	$ (800,000)
Future minimum payments under non-cancelable agreements [Abstract]
2014	13,114,000
2015	13,120,000
2016	13,048,000
2017	13,187,000
2018	12,872,000
2019 and beyond	75,478,000
Total future lease payments	140,819,000
Rent expense	15,600,000	13,100,000	12,400,000
Operating Leases, Future Minimum Payments Receivable [Abstract]
2014	5,038,000
2015	4,523,000
2016	2,968,000
2017	2,005,000
2018	727,000
2019 and beyond	1,037,000
Total minimum rental receipts	16,298,000
Rent income	$ 5,600,000	$ 6,100,000	$ 6,100,000
Towers [Member]
Operating Leased Assets [Line Items]
Number of renewals	4
Term of renewals	5 years
Towers [Member] | Minimum [Member]
Operating Leased Assets [Line Items]
Terms of leases	5 years
Towers [Member] | Maximum [Member]
Operating Leased Assets [Line Items]
Terms of leases	10 years
Other [Member] | Minimum [Member]
Operating Leased Assets [Line Items]
Terms of leases	5 years
Other [Member] | Maximum [Member]
Operating Leased Assets [Line Items]
Terms of leases	20 years