Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Cash flows from operating activities:
Net income (loss)	$ 86,268	$ 81,138	$ (15,671)
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Amortization of deferred financing costs	466	333	292
Amortization of investment discount/premium	146	296	298
Depreciation and amortization	109,154	104,861	54,543
Deferred income taxes	(13,431)	(8,037)	(16,322)
Stock-based compensation	14,610	12,160	15,532
Impairment of right-of-use lease assets	848	6,046	0
Impairment of intangible assets	0	0	19,909
Changes in assets and liabilities:
Tuition receivable, net	19,659	1,770	7,880
Other assets	(32,326)	(2,129)	3,633
Accounts payable and accrued expenses	(22,685)	245	1,140
Income taxes payable and income taxes receivable	(4,020)	1,198	(516)
Contract liabilities	(10,095)	7,716	(19,329)
Other long-term liabilities	(5,689)	(3,451)	(4,522)
Net cash provided by operating activities	142,905	202,146	46,867
Cash flows from investing activities:
Cash paid for acquisition, net of cash acquired	(628,759)	0	167,859
Purchases of property and equipment	(46,812)	(38,689)	(27,547)
Purchases of marketable securities	(1,863)	(40,481)	(25,304)
Proceeds from marketable securities	36,192	43,762	16,367
Other investments	(950)	(2,658)	(1,238)
Net cash provided by (used in) investing activities	(642,192)	(38,066)	130,137
Cash flows from financing activities:
Net proceeds from issuance of common stock	220,248	0	0
Proceeds from long-term debt	145,630	0	0
Common dividends paid	(55,956)	(46,625)	(27,842)
Net payments for stock awards	(24,741)	(9,195)	7,789
Payments on long-term debt	(3,807)	0	0
Payment of deferred financing costs	(1,940)	0	(1,162)
Repurchase of common stock	(247)	0	0
Net cash provided by (used in) financing activities	279,187	(55,820)	(21,215)
Effect of exchange rate changes on cash, cash equivalents, and restricted cash	1,623	0	0
Net increase (decrease) in cash, cash equivalents, and restricted cash	(218,477)	108,260	155,789
Cash, cash equivalents, and restricted cash - beginning of period	420,497	312,237	156,448
Cash, cash equivalents, and restricted cash - end of period	202,020	420,497	312,237
Noncash transactions:
Non-cash additions to property and equipment	$ 4,079	$ 5,562	$ 1,029