Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Cash flows from operating activities:
Net income	$ 67,535	$ 23,560
Adjustments to reconcile net income to net cash provided by operating activities:
Deferred income taxes	(3,277)	(8,682)
Depreciation and amortization of property and equipment	62,688	60,482
Stock-based compensation expense	10,290	21,544
Amortization of debt issuance costs	2,367	3,618
Accretion of asset retirement obligations	146	138
Loss on extinguishment of debt	3,183	16,417
Changes in operating assets and liabilities:
Restricted cash	665	539
Accounts receivable	(13,201)	(4,489)
Other assets	(730)	(1,141)
Customer deposits	(665)	(539)
Accrued compensation	(18,673)	(1,382)
Accounts payable and accrued other expenses	1,144	(4,352)
Estimated liability for refunds and appeals	(4,568)	2,821
Other long-term liabilities	337	146
Other	(78)	(335)
Net cash provided by operating activities	107,163	108,345
Cash flows from investing activities:
Expenditures for property and equipment	(23,610)	(22,578)
Business combinations, net of cash acquired	(69,731)
Other investing activities		1,181
Net cash used in investing activities	(93,341)	(21,397)
Cash flows from financing activities:
Net proceeds from issuance of common stock		226,963
Proceeds from exercise of stock options	12,349	56
Proceeds from issuance of debt		800,000
Dividends paid		(150,000)
Payment of debt issuance costs	(661)	(6,327)
Repayment of debt	(13,500)	(1,062,850)
Net cash used in financing activities	(1,812)	(192,158)
Effect of foreign exchanges on cash and cash equivalents	363	(385)
Net increase (decrease) in cash and cash equivalents	12,373	(105,595)
Cash and cash equivalents at beginning of period	110,635	149,365
Cash and cash equivalents at end of the period	123,008	43,770
Supplemental disclosures of cash flow information:
Cash paid for income taxes	22,357	24,377
Cash paid for interest	22,161	35,927
Noncash investing activities (accrued property and equipment purchases)	12,611	12,000
Noncash investing activities (business combinations)	$ 286
Noncash financing activities (accrued debt issuance costs)		$ 979