Equity Incentive Awards (Tables)

12 Months Ended

Dec. 31, 2017

Disclosure of Compensation Related Costs, Share-based Payments [Abstract]

Schedule of Share-based Compensation, Restricted Stock and Restricted Stock Units Activity

A summary of our restricted stock activity, and related information for the years ended December 31, 2017, 2016, and 2015 follows:

	Number of Shares		Weighted Average Grant Date Fair Value
Balance at December 31, 2014	102,225		41.09
Shares granted	158,014		54.68
Shares vested	(174,739	)	49.17
Balance at December 31, 2015	85,500		49.72
Shares granted	133,717		68.21
Shares vested	(153,610	)	59.85
Balance at December 31, 2016	65,607		63.68
Shares granted	130,426		76.25
Shares forfeited	(990	)	80.54
Shares vested	(125,271	)	68.79
Balance at December 31, 2017	69,772		77.77

Summary of Stock Option Activity

Note 14—Equity Incentive Awards (continued)

A summary of our stock option activity, and related information for the years ended December 31, 2017, 2016 and 2015 follows:

	Shares Subject To Options		Weighted Average Exercise Price Per Share		Weighted Average Outstanding Contractual Life (in years)
Balance at December 31, 2014	1,085,600		$	21.95	2.1
Options exercised	(220,000	)	17.35
Balance at December 31, 2015	865,600		23.12		1.6
Options issued	7,550		10.70
Options exercised	(440,000	)	25.66
Balance at December 31, 2016	433,150		21.44		1.7
Options issued	6,930		11.00
Options exercised	(220,000	)	22.05
Balance at December 31, 2017	220,080		18.32		1.5
Exercisable at December 31, 2017	212,966		20.84		1.4

Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions

The fair value of each grant is estimated on the grant date using the Black-Scholes-Merton model. The following table includes the assumptions that were made and the estimated fair values:                

	2017
Dividend Yield	2.4		%
Risk-free interest rate	1.9		%
Expected Life	5.5 years
Expected Volatility	17.8		%
Estimated Grant Date Fair Value of Options	$	76,230