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Consolidated Statements of Equity - USD ($) shares in Thousands, $ in Thousands | Total | Common Stock [Member] | Additional Paid-in Capital [Member] | Retained Earnings [Member]
--- | --- | --- | --- | ---
Balance at Dec. 31, 2016 |  | $ 2,760,767 | $ 937 | $ 974,304 | $ 1,785,526
Balance, Shares at Dec. 31, 2016 |  |  | 93,718 |  |
Net income (loss) |  | 320,372 |  |  | 320,372
Common stock issued under employee stock option, employee stock purchase plan and stock purchase plan |  | 23,276 | $ 5 | 23,271 |
Common stock issued under employee stock option, employee stock purchase plan and stock purchase plan, shares |  |  | 528 |  |
Issuance of restricted stock |  |  | $ 5 | (5) |
Issuance of restricted stock, shares |  |  | 536 |  |
Issuance of restricted stock for acquisition consideration |  | 2,658 | $ 1 | 2,657 |
Issuance of restricted stock for acquisition consideration, shares |  |  | 69 |  |
Stock-based compensation expense |  | 29,573 |  | 29,573 |
Forfeitures of restricted stock |  |  | $ (1) | 1 |
Forfeitures of restricted stock, shares |  |  | (92) |  |
Repurchased common stock |  | (70,192) | $ (10) | (12,473) | (57,709)
Repurchased common stock, shares |  |  | (1,038) |  |
Balance at Dec. 31, 2017 |  | 3,066,454 | $ 937 | 1,017,328 | 2,048,189
Balance, Shares at Dec. 31, 2017 |  |  | 93,721 |  |
Net income (loss) |  | 268,629 |  |  | 268,629
Common stock issued under employee stock option, employee stock purchase plan and stock purchase plan |  | 18,919 | $ 5 | 18,914 |
Common stock issued under employee stock option, employee stock purchase plan and stock purchase plan, shares |  |  | 495 |  |
Issuance of restricted stock |  |  | $ 8 | (8) |
Issuance of restricted stock, shares |  |  | 770 |  |
Stock-based compensation expense |  | 38,703 |  | 38,703 |
Stock swaps |  | (2,661) | $ (1) | (2,660) |
Stock swaps, shares |  |  | (56) |  |
Forfeitures of restricted stock |  |  | $ (1) | 1 |
Forfeitures of restricted stock, shares |  |  | (69) |  |
Repurchased common stock |  | (302,160) | $ (70) | (79,631) | (222,459)
Repurchased common stock, shares |  |  | (7,041) |  |
Balance at Dec. 31, 2018 |  | 3,087,884 | $ 878 | 992,647 | 2,094,359
Balance, Shares at Dec. 31, 2018 |  |  | 87,820 |  |
Net income (loss) |  | (1,497,702) |  |  | (1,497,702)
Unrealized holding gain on investments, net of tax | [1] | 78 |  |  | 78
Common stock issued under employee stock option, employee stock purchase plan and stock purchase plan |  | 11,947 | $ 5 | 11,942 |
Common stock issued under employee stock option, employee stock purchase plan and stock purchase plan, shares |  |  | 533 |  |
Issuance of restricted stock |  |  | $ 11 | (11) |
Issuance of restricted stock, shares |  |  | 1,113 |  |
Stock-based compensation expense |  | 42,758 |  | 42,758 |
Stock swaps |  | (689) | $ 0 | (689) |
Stock swaps, shares |  |  | (20) |  |
Forfeitures of restricted stock |  |  | $ (1) | 1 |
Forfeitures of restricted stock, shares |  |  | (132) |  |
Repurchased common stock |  | (145,280) | $ (51) | (58,706) | (86,523)
Repurchased common stock, shares |  |  | (5,066) |  |
Balance at Dec. 31, 2019 |  | $ 1,498,996 | $ 842 | $ 987,942 | $ 510,212
Balance, Shares at Dec. 31, 2019 |  |  | 84,248 |  |
[1] | Presented within retained earnings on both the Consolidated Balance Sheets and the Consolidated Statements of Equity as the balance is immaterial.

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