Consolidated Statements of Financial Position (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Statement of Financial Position [Abstract]
Accounts receivable, allowances	$ 27,678	$ 33,181
Preferred stock, par value (usd per share)	$ 0.001	$ 0.001
Preferred stock, authorized (in shares)	5,000,000	5,000,000
Preferred stock, issued (in shares)	0	0
Preferred stock, outstanding (in shares)	0	0
Common stock, par value (usd per share)	$ 0.001	$ 0.001
Common stock, authorized (in shares)	260,000,000	260,000,000
Common stock, issued (in shares)	119,078,491	124,261,458
Common stock, outstanding (in shares)	119,078,491	124,261,458