Consolidated Statements of Equity and Redeemable Non-controlling Interest - USD ($) $ in Thousands	Total		Common shares	Additional Paid- in Capital	Retained Earnings	Accumulated Other Comprehensive Income (Loss)	Redeemable non-controlling interest	Total Equity
Beginning balance, value (in shares) at Dec. 31, 2013			231,262,576
Beginning balance, value at Dec. 31, 2013	$ 1,324,068		$ 2,310	$ 1,268,344	$ 511,699	$ (459,614)	$ 1,329
Net settlement on issuance of common shares on exercise of options (in shares)	3,972,535	[1]	3,319,760
Net settlement on issuance of common shares on exercise of options	$ 16,051		$ 33	16,018
Issuance of common shares under the employee stock purchase plan (in shares)			151,461
Issuance of common shares under the employee stock purchase plan	2,347		$ 2	2,345
Net settlement on vesting of restricted share units	(2,358)		$ 3	(2,361)
Net settlement on vesting of restricted share units, shares			329,311
Net settlement on vesting of performance units	(15,672)		$ 9	(15,681)
Net settlement on vesting of performance units, shares			913,939
Stock repurchased and retired	(302,625)		$ (173)		(302,452)
Stock repurchased and retired, shares			(17,292,842)
Excess tax benefit on stock-based Compensation	0
Expenses related to stock purchase	(2,543)				(2,543)
Distribution to non-controlling interest	(1,487)						(1,487)
Stock-based compensation expense	28,065			28,065
Comprehensive income:
Net income (loss)	192,171				192,002		169	$ 192,002
Other comprehensive income	47,119					47,130	(11)	47,130
End balance, value (in shares) at Dec. 31, 2014			218,684,205
End balance, value at Dec. 31, 2014	1,285,136		$ 2,184	1,296,730	398,706	(412,484)
Comprehensive income:
Net income (loss)	$ 192,171				192,002		169	192,002
Net settlement on issuance of common shares on exercise of options (in shares)	1,428,605		1,428,605
Net settlement on issuance of common shares on exercise of options	$ 13,564		$ 14	13,550
Issuance of common shares under the employee stock purchase plan (in shares)			121,485
Issuance of common shares under the employee stock purchase plan	2,524		$ 1	2,523
Net settlement on vesting of restricted share units	(2,306)		$ 3	(2,309)
Net settlement on vesting of restricted share units, shares			259,776
Net settlement on vesting of performance units			$ 8	(8)
Net settlement on vesting of performance units, shares			846,114
Stock repurchased and retired	$ (226,917)		$ (99)		(226,818)
Stock repurchased and retired, shares	(9,867,873)		(9,867,873)
Excess tax benefit on stock-based Compensation	$ 6,560			6,560
Expenses related to stock purchase	(197)				(197)
Stock-based compensation expense	24,976			24,976
Net income (loss)	239,817				239,817			239,817
Other comprehensive income	$ (38,801)					(38,801)		(38,801)
End balance, value (in shares) at Dec. 31, 2015	211,472,312		211,472,312
End balance, value at Dec. 31, 2015	$ 1,304,356		$ 2,111	1,342,022	411,508	(451,285)		1,304,356
Comprehensive income:
Net income (loss)	$ 239,817				239,817			239,817
Net settlement on issuance of common shares on exercise of options (in shares)	994,155		994,155
Net settlement on issuance of common shares on exercise of options			$ 10	14,886				14,896
Issuance of common shares under the employee stock purchase plan (in shares)			146,685
Issuance of common shares under the employee stock purchase plan			$ 1	3,331				3,332
Net settlement on vesting of restricted share units			$ 1	(884)				(883)
Net settlement on vesting of restricted share units, shares			121,682
Stock repurchased and retired			$ (139)		(345,061)			(345,200)
Stock repurchased and retired, shares	(13,940,782)		(13,940,782)
Excess tax benefit on stock-based Compensation	$ 0
Expenses related to stock purchase	(279)				(279)			(279)
Stock-based compensation expense				25,113				25,113
Redeemable non-controlling interest							3,910
Change in fair value of redeemable non-controlling interest					(2,643)		2,643	(2,643)
Deferred tax assets recognized on early adoption of ASU 2016-09					24,912			24,912
Net income (loss)	$ 267,547				269,684		(2,137)	269,684
Other comprehensive income						(6,640)	104	(6,640)
End balance, value (in shares) at Dec. 31, 2016	198,794,052		198,794,052
End balance, value at Dec. 31, 2016			$ 1,984	$ 1,384,468	358,121	$ (457,925)	4,520	1,286,648
Comprehensive income:
Net income (loss)	$ 267,547				$ 269,684		$ (2,137)	$ 269,684

[1] 2,138,601 of these options were net settled upon exercise by issuing 1,485,826 shares (net of minimum statutory withholding taxes).