CONSOLIDATED BALANCE SHEETS (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Statement of Financial Position [Abstract]
Property and equipment, Accumulated depreciation	$ 59,404	$ 57,103
Common stock, shares authorized (in shares)	180,000,000	180,000,000
Common stock, issued (in shares)	74,342,826	92,332,565
Common stock, outstanding (in shares)	74,342,826	75,329,557
Treasury stock, shares (in shares)		17,003,008