Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Statement of Financial Position [Abstract]
Accounts receivable, allowance for doubtful accounts	$ 32,506	$ 21,903
Par value (in usd per share)	$ 0.001	$ 0.001
Shares authorized (in shares)	475,000,000	475,000,000
Shares issued (in shares)	121,259,960	120,539,041
Shares outstanding (in shares)	91,836,938	92,376,335
Treasury stock, shares	29,423,022	28,162,706