Condensed Statements of Cash Flows (Unaudited) - USD ($)	6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
Cash flows from operating activities:
Net income	$ 468,935,000	$ 280,982,000
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	127,942,000	131,170,000
Loss on disposal of property and equipment	701,000	140,000
Other, net	15,352,000	(9,118,000)
Changes in operating assets and liabilities, net	(104,639,000)	113,042,000
Net cash provided by operating activities	508,291,000	516,216,000
Cash flows from investing activities:
Purchase of property and equipment	(206,109,000)	(120,128,000)
Proceeds from sale of property and equipment	15,512,000	2,570,000
Purchase of short-term investments	(89,965,000)
Proceeds from maturities of short-term investments	255,072,000
Net cash used in investing activities	(25,490,000)	(117,558,000)
Cash flows from financing activities:
Proceeds from issuance of long-term debt		99,923,000
Payments for share repurchases	(280,215,000)	(306,791,000)
Forward contract for accelerated share repurchases	(68,750,000)	(37,500,000)
Dividends paid	(46,408,000)	(35,892,000)
Other financing activities, net	(4,654,000)	(3,345,000)
Net cash used in financing activities	(400,027,000)	(283,605,000)
Increase in cash and cash equivalents	82,774,000	115,053,000
Cash and cash equivalents at beginning of period	401,430,000	403,571,000
Cash and cash equivalents at end of period	$ 484,204,000	$ 518,624,000