Commitments and Contingencies (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Other Commitments [Line Items]
Rent expense	$ 8,509,000	$ 8,444,000	$ 8,513,000
Boulder Station Lease [Member]
Other Commitments [Line Items]
Land subject to ground leases	27
Ground lease, monthly rental payments	222,933
Ground lease, intervals between options to purchase land	5 years
Boulder Station Lease [Member] | Fair Market Value [Member]
Other Commitments [Line Items]
Ground lease, period between rent adjustments	10 years
Ground lease, minimum increase to fair market value adjustment (percent)	8.00%
Boulder Station Lease [Member] | Cost of Living Factor [Member]
Other Commitments [Line Items]
Ground lease, period between rent adjustments	10 years
Texas Station Lease [Member]
Other Commitments [Line Items]
Land subject to ground leases	47
Ground lease, monthly rental payments	337,417
Ground lease, intervals between options to purchase land	5 years
Texas Station Lease [Member] | Fair Market Value [Member]
Other Commitments [Line Items]
Ground lease, period between rent adjustments	10 years
Ground lease, minimum increase to fair market value adjustment (percent)	8.00%
Texas Station Lease [Member] | Cost of Living Factor [Member]
Other Commitments [Line Items]
Ground lease, period between rent adjustments	10 years
Wild Wild West Lease [Member]
Other Commitments [Line Items]
Land subject to ground leases	20
Ground lease, monthly rental payments	$ 125,637
After January 2020 [Member] | Wild Wild West Lease [Member]
Other Commitments [Line Items]
Ground lease, period between rent adjustments	3 years
Maximum [Member] | Boulder Station Lease [Member]
Other Commitments [Line Items]
Ground lease, term	65 years
Maximum [Member] | Texas Station Lease [Member]
Other Commitments [Line Items]
Ground lease, term	65 years