Business Combinations - Assets Acquired and Liabilities Assumed (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Apr. 05, 2017	Dec. 31, 2016
Business Acquisition [Line Items]
Goodwill	$ 787,803		$ 615,433
Community Education Centers
Business Acquisition [Line Items]
Accounts Receivable		$ 29,936
Prepaid and other current assets		5,032
Property and equipment		126,510
Intangible assets		76,000
Favorable lease assets		3,110
Deferred income tax assets		2,223
Other non-current assets		4,327
Total assets acquired		247,138
Accounts payable and accrued expenses		53,800
Unfavorable lease liabilities		1,299
Other non-current liabilities		9,917
Total liabilities assumed		65,016
Total identifiable net assets		182,122
Goodwill		172,343
Total consideration paid, net of cash acquired		$ 354,465