Equity Incentive Plan (Details) - Restricted Stock [Member] shares in Thousands	6 Months Ended
	Jun. 30, 2018 $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares Outstanding, Unvested restricted stock at beginning of the period | shares	227
Shares Outstanding, Restricted stock granted | shares	50
Shares Outstanding, Restricted stock vested | shares	(65)
Shares Outstanding, Restricted stock forfeited | shares	0
Shares Outstanding, Unvested restricted stock at end of the period | shares	212
Weighted Average Grant Date Fair Value, Unvested restricted stock at beginning of the period (in dollars per share) | $ / shares	$ 39.47
Weighted Average Grant Date Fair Value, Restricted stock granted (in dollars per share) | $ / shares	47.73
Weighted Average Grant Date Fair Value, Restricted stock vested (in dollars per share) | $ / shares	35.41
Weighted Average Grant Date Fair Value, Restricted stock forfeited (in dollars per share) | $ / shares	48.62
Weighted Average Grant Date Fair Value, Unvested restricted stock at end of the period (in dollars per share) | $ / shares	$ 42.74