Convertible Senior Notes (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016	Dec. 31, 2014
Debt Instrument [Line Items]
Temporary equity	$ 0	$ 79,495
Additional paid-in capital	4,882,838	4,761,588
Senior Notes Due 2019 [Member]
Debt Instrument [Line Items]
Principal	1,437,483	1,437,500
Less: note discount and issuance costs	(79,903)	(89,344)
Net carrying amount	1,357,580	1,348,156	$ 1,440,000
Temporary equity	0	79,495
Additional paid-in capital	162,869	83,374
Total equity (including temporary equity)	$ 162,869	$ 162,869