Consolidated Statements of Stockholders Equity and Other Comprehensive Income (Loss) - USD ($) $ in Thousands	Total	Common stock	Treasury stock	Additional Paid-in Capital	Accumulated Dividends	Accumulated Other Comprehensive Income (Loss)	Retained Earnings (Accumulated Deficit)	Public offering	Public offering Common stock	Public offering Additional Paid-in Capital	At The Market (ATM)	At The Market (ATM) Common stock	At The Market (ATM) Additional Paid-in Capital
Beginning balance at Dec. 31, 2014	$ 2,270,131	$ 57	$ (11,411)	$ 3,334,305	$ (424,387)	$ (332,443)	$ (295,990)
Beginning Balance, shares at Dec. 31, 2014		56,505,122	(53,867)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	187,774						187,774
Total other comprehensive income (loss), net of tax	(176,616)					(176,616)
Issuance of common stock in public offering of common stock, net								$ 829,496	$ 3	$ 829,493
Issuance of common stock in public offering of common stock, shares									2,994,792
Issuance of common stock and release of treasury stock for employee equity awards	30,040	$ 1	$ 1,546	28,493
Issuance of common stock and release of treasury stock for employee equity awards, shares		856,406	7,348
Issuance of common stock and release of treasury stock for the exchanges and conversions of 4.75% convertible debt	7,884		$ 2,492	5,392
Issuance of common stock and release of treasury stock for the exchanges and conversions of 4.75% convertible debt (in shares)		90,163	11,784
Issuance of common stock and cash payment for special distribution	(125,707)	$ (1)		(501,513)	627,221
Issuance of common stock for special distribution, shares		1,688,411
Dividend distributions	(393,584)				(393,584)
Settlement of accrued dividends on vested equity awards	3,775			3,775
Accrued dividends on unvested equity awards	(23,280)				(23,280)
Tax benefit from employee stock plans	30			30
Stock-based compensation, net of estimated forfeitures	135,443			135,443
Ending balance at Dec. 31, 2015	2,745,386	$ 62	$ (7,373)	4,838,444	(1,468,472)	(509,059)	(108,216)
Ending Balance, shares at Dec. 31, 2015		62,134,894	(34,735)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	126,800						126,800
Total other comprehensive income (loss), net of tax	(440,083)					(440,083)
Issuance of common stock and release of treasury stock for employee equity awards	34,675	$ 1	$ 1,502	33,172
Issuance of common stock and release of treasury stock for employee equity awards, shares		847,374	7,099
Issuance of common stock for TelecityGroup acquisition	2,077,912	$ 7		2,077,905
Issuance of common stock for TelecityGroup acquisition (in shares)		6,853,500
Issuance of common stock and release of treasury stock for the exchanges and conversions of 4.75% convertible debt	150,025	$ 2	$ (141,688)	291,711
Issuance of common stock and release of treasury stock for the exchanges and conversions of 4.75% convertible debt (in shares)		1,981,662	(380,779)
Dividend distributions	(492,403)				(492,403)
Settlement of accrued dividends on vested equity awards	7,270			8,270	(1,000)
Accrued dividends on unvested equity awards	(7,770)				(7,770)
Tax benefit from employee stock plans	2,773			2,773
Stock-based compensation, net of estimated forfeitures	161,244			161,244
Ending balance at Dec. 31, 2016	$ 4,365,829	$ 72	$ (147,559)	7,413,519	(1,969,645)	(949,142)	18,584
Ending Balance, shares at Dec. 31, 2016	71,409,015	71,817,430	(408,415)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Adjustment from adoption of new accounting standard	$ 1,123						1,123
Net income	232,982						232,982
Total other comprehensive income (loss), net of tax	163,953					163,953
Issuance of common stock in public offering of common stock, net								$ 2,126,339	$ 6	$ 2,126,333	$ 355,082		$ 355,082
Issuance of common stock in public offering of common stock, shares									6,069,444		763,201	763,201
Issuance of common stock and release of treasury stock for employee equity awards	41,689	$ 1	$ 1,239	40,449
Issuance of common stock and release of treasury stock for employee equity awards, shares		790,329	6,073
Dividend distributions	(612,085)				(612,085)
Settlement of accrued dividends on vested equity awards	3,390			4,280	(890)
Accrued dividends on unvested equity awards	(10,172)				(10,172)
Stock-based compensation, net of estimated forfeitures	181,660			181,660
Ending balance at Dec. 31, 2017	$ 6,849,790	$ 79	$ (146,320)	$ 10,121,323	$ (2,592,792)	$ (785,189)	$ 252,689
Ending Balance, shares at Dec. 31, 2017	79,038,062	79,440,404	(402,342)