Consolidated Statements of Cash Flows (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Cash Flows From Operating Activities
Net income	$ 28.4	$ 25.4
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	96.9	87.8
Deferred income taxes	(14.7)	(10.1)
Share-based compensation expense	20.0	12.7
Excess tax benefits from share-based compensation arrangements	(20.2)	(15.1)
Other operating activities	2.8	2.0
Changes in operating assets and liabilities:
Accounts receivable	(1.8)	3.9
Prepaid expenses and other current assets	0.8	3.3
Accounts payable, accrued expenses, and other current liabilities	26.9	30.3
Deferred revenue	4.3	(2.1)
Deferred rent	0.4	2.3
Other non-current assets and liabilities	1.5	1.3
Net cash provided by operating activities	145.3	141.7
Cash Flows From Investing Activities
Purchases of property and equipment	(92.5)	(85.0)
All other investing activities	0.7	0.5
Net cash used in investing activities	(91.8)	(84.5)
Cash Flows From Financing Activities
Principal payments of capital and build-to-suit leases	(5.6)	(12.5)
Repayments of debt	(25.1)	(0.1)
Payments for deferred acquisition obligations	(0.1)	(0.1)
Receipt of Texas Enterprise Fund grant	0	5.5
Shares of common stock withheld for employee taxes	0	(13.6)
Proceeds from employee stock plans	21.8	2.1
Excess tax benefits from share-based compensation arrangements	20.2	15.1
Net cash provided by (used in) financing activities	11.2	(3.6)
Effect of exchange rate changes on cash and cash equivalents	(2.5)	0.5
Increase in cash and cash equivalents	62.2	54.1
Cash and cash equivalents, beginning of period	213.5	259.7
Cash and cash equivalents, end of period	275.7	313.8
Supplemental Cash Flow Information
Cash payments for interest, net of amount capitalized	0.3	0.5
Cash payments for income taxes, net of refunds	$ 3.8	$ 0.9