Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015
Cash flow from operating activities:
Net income	$ 35,226	$ 65,374
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	113,440	52,103
Stock-based compensation expense	27,913	8,314
Income tax benefit related to exercise of stock options	(23,760)	(5,065)
Amortization and write-offs of loan origination costs	5,312	2,874
Loss on sale or disposition of property and equipment	150	209
Deferred income taxes	(24,056)	(7,395)
Provision for doubtful accounts	1,257	299
Changes in operating assets and liabilities, excluding effects from acquisitions:
Accounts receivable	(13,458)	(1,804)
Prepaid expenses and other assets	(1,516)	2,488
Accounts payable	7,870	(2,405)
Accrued expenses	(25,851)	(20,186)
Income taxes prepaid and payable	23,757	11,064
Deferred revenue	13,052	(5,148)
Net cash provided by operating activities	139,336	100,722
Cash flow from investing activities:
Additions to property and equipment	(13,593)	(5,750)
Proceeds from sale of property and equipment	43
Cash paid for business acquisitions, net of cash acquired	(317,554)	(7,863)
Additions to capitalized software	(3,306)	(1,792)
Purchase of long-term investment	(1,000)
Net cash used in investing activities	(335,410)	(15,405)
Cash flow from financing activities:
Repayments of debt	(155,325)	(174,000)
Proceeds from exercise of stock options	19,212	8,735
Withholding taxes related to equity award net share settlement	(4,615)
Income tax benefit related to exercise of stock options	23,760	5,065
Proceeds from common stock issuance, net		717,866
Purchase of common stock for treasury	(11)
Payment of fees related to refinancing activities	(222)
Dividends paid on common stock	(24,790)	(21,101)
Net cash (used in) provided by financing activities	(141,991)	536,565
Effect of exchange rate changes on cash and cash equivalents	(872)	(1,651)
Net (decrease) increase in cash and cash equivalents	(338,937)	620,231
Cash and cash equivalents, beginning of period	434,159	109,577
Cash and cash equivalents, end of period	$ 95,222	$ 729,808