Consolidated Statements of Cash Flows - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	$ 26.5	$ 23.3	$ 18.5
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization expense	267.2	280.7	239.7
Stock-based compensation expense, net of capitalized stock-based compensation expense	18.2	18.8	14.7
Amortization of aerial image library, deferred contract costs and lease incentive	18.5	17.8	18.1
Deferred income taxes	18.0	9.2	6.7
Excess tax benefit from share-based compensation	(1.3)	(1.0)	(3.0)
Loss from early extinguishment of debt	35.7
Amortization of debt issuance costs, accretion of debt discount, and other	11.2	5.8	1.8
Changes in working capital, net of assets acquired and liabilities assumed in business combinations:
Accounts receivable, net	(4.8)	42.8	(14.7)
Deferred contract costs	(16.9)	(18.5)	(7.2)
Other current and non-current assets	(15.1)	3.2	2.0
Accounts payable	(2.5)	(3.7)	(23.1)
Accrued liabilities	8.7	13.1	4.2
Deferred revenue	(61.8)	(61.8)	(32.8)
Net cash flows provided by operating activities	301.6	329.7	224.9
CASH FLOWS FROM INVESTING ACTIVITIES:
Construction in progress additions	(191.7)	(160.9)	(222.2)
Property and equipment additions	(0.3)	(2.5)	(11.8)
Acquisition of businesses, net of cash acquired	(140.0)		(35.7)
Decrease (increase) in restricted cash	0.7	(1.6)	5.1
Investment in joint venture	(10.0)	(5.0)
Other	3.0	0.1
Net cash flows used in investing activities	(338.3)	(169.9)	(264.6)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from issuance of debt	1,275.0
Cash received from revolving credit facility	110.0
Repayment of debt, revolving credit facility and capital lease obligations	(1,212.3)	(6.6)	(6.6)
Cash paid for debt issuance costs, original issue discount, modification and early extinguishment of long-term debt	(37.6)	(3.0)
Repurchase of common stock	(115.7)	(144.5)	(75.1)
Proceeds from exercise of stock options	3.2	5.6	11.1
Preferred stock dividend payment	(4.0)	(4.0)	(4.0)
Excess tax benefit from share-based compensation	1.3	1.0	3.0
Net cash flows provided by (used in) financing activities	19.9	(151.5)	(71.6)
Net (decrease) increase in cash and cash equivalents	(16.8)	8.3	(111.3)
Cash and cash equivalents, beginning of period	126.1	117.8	229.1
Cash and cash equivalents, end of period	109.3	126.1	117.8
SUPPLEMENTAL CASH FLOW INFORMATION:
Cash paid for interest, net of capitalized amounts of $55.6, $32.1 million and $49.5, respectively	14.0	24.0
Cash paid (refunded) for income taxes	0.1	(0.5)	(11.0)
NON-CASH INVESTING AND FINANCING ACTIVITIES:
Changes to non-cash property, equipment and construction in progress accruals, including interest	11.2	(9.2)	16.5
Additions to capital lease obligations		(6.9)	(3.1)
Non-cash preferred stock dividend accrual	$ (1.0)	$ (1.0)	$ (1.0)