Summary of Significant Accounting Policies (Tables)

9 Months Ended

Sep. 30, 2016

The following table presents the number of shares or units outstanding for each award type as of September 30, 2016 and December 31, 2015, respectively, (in thousands):



Award type	September 30, 2016	December 31, 2015
Stock options	768	829
Restricted stock units (time-based)	2,250	1,915
Restricted stock units (performance-based)	—	24
Restricted stock units (market-based)	460	—
Stock appreciation rights	516	522
Market stock units	342	563

Fair value assumptions - market-based RSUs [Table Text Block]

The assumptions used to value the market-based RSUs granted during the three and nine months ended September 30, 2016 were as follows:



		September 30, 2016
Volatility		44.98%
Risk-free interest rate		1.08%
Dividend yield		—

The fair value of the market-based RSUs is expensed over the derived service period for each separate vesting tranche. The derived service period for the vesting tranches of the market-based RSUs ranges between 1.01 and 1.98 years.

Market Stock Units Valuation Assumptions [Table Text Block]

The weighted average assumptions used to value the MSUs granted during the three and nine months ended September 30, 2016 were as follows:



		September 30, 2016
Volatility		44.06%
Risk-free interest rate		1.04%
Expected option life in years		2.93
Dividend yield		—