Corporate Income Taxes - Components of Deferred Tax Assets, Net (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Deferred tax assets
Basis differences in depreciation and amortization	$ 10,073	$ 6,578
Deferred lease liabilities	23,527	24,345
Deferred revenue	8,247	10,974
Deferred compensation expense incurred in connection with stock options	994	1,589
Federal and state net operating loss carry-forwards	8,473	10,430
Accruals, reserves and other	7,297	7,654
Deferred tax assets, gross	58,611	61,570
Deferred tax liabilities
Deferred costs	803	1,751
Change in accounting method	3,147	6,621
Undistributed foreign earnings and other	529	622
Deferred tax liabilities, gross	4,479	8,994
Gross deferred tax assets	54,132	52,576
Valuation allowance	(54,193)	(52,637)
Deferred tax liabilities, net	$ (61)	$ (61)