Stock-Based Compensation (Tables)

As of March 31, 2016, the unrecognized compensation cost and remaining weighted-average amortization period related to stock-based awards were as follows:

							Performance-
							based
					Restricted		Restricted
		Stock	Restricted		Stock		Stock
(in thousands)		Options	Shares		Units		Units⁽¹⁾
Unrecognized compensation cost		$ 3,616		$ 1		$ 11,627		$ 5,852
Remaining weighted-average
amortization period	1.8 years		0.1 years			2.9 years		2.2 years

⁽¹⁾ Based on the probable achievement of the performance goals identified in each award.

The weighted-average assumptions used to value the options granted during the three months ended March 31, 2015 were as follows (in thousands):

Options granted			289
Expected term of options			6.4 years
Expected volatility			35%
Risk-free interest rate			1.886%
Dividend yield			zero

The following table summarizes activities relating to the Company’s stock options:

			Weighted-
		Weighted-	Average
		Average	Remaining	Aggregate
	Number of	Exercise	Contractual	Intrinsic
(in thousands, except per share data)	Options	Price	Term (Years)	Value
Outstanding as of December 31, 2015	2,580	$20.49
Exercised	(47)	15.97
Forfeited or expired	(270)	23.20
Outstanding as of March 31, 2016	2,263	$20.27	4.91	$ 7,738
Exercisable as of March 31, 2016	1,789	$19.79	3.43	$ 7,256

The following table summarizes activities related to the Company’s restricted shares:

		Weighted-
		Average
	Number of	Grant Date
(in thousands, except per share data)	Shares	Fair Value
Non-vested shares outstanding as of December 31, 2015	38	$15.38
Vested	(37)	15.38
Non-vested shares outstanding as of March 31, 2016	1	$14.78

The following table summarizes the activities related to the Company’s time-based restricted stock units:

		Weighted-
		Average
	Number of	Grant Date
(in thousands, except per share data)	Units	Fair Value
Non-vested awards outstanding as of December 31, 2015	467	$21.59
Granted	266	21.64
Vested	(149)	20.69
Forfeited	(8)	22.61
Non-vested awards outstanding as of March 31, 2016	576	$21.83

The following table summarizes the activities related to the Company’s performance-based restricted stock units:

		Weighted-
		Average
	Number of	Grant Date
(in thousands, except per share data)	Units	Fair Value
Non-vested units outstanding as of December 31, 2015	306	$19.77
Granted ⁽¹⁾	183	21.64
Forfeited or expired	(98)	16.91
Non-vested units outstanding as of March 31, 2016	391	$21.36

⁽¹⁾Represents target number of units that can vest based on the achievement of the performance goals.