Income Taxes (Narrative) (Details) - USD ($)	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Operating Loss Carryforwards [Line Items]
Income before taxes	$ 56,408,000	$ 62,197,000	$ 70,126,000	$ 63,035,000	$ 61,802,000	$ 65,258,000	$ 63,031,000	$ 56,340,000	$ 251,765,000	$ 246,431,000	$ 224,440,000
Tax benefits from stock-based compensation arrangements									(1,900,000)	(594,000)	(831,000)
AMT credt carryforward	1,498,000				1,177,000				1,498,000	1,177,000
Unrecognized Tax Benefits	0				$ 0				0	0
Unrecognized Tax Benefits, Period Increase (Decrease)									0
Unrecognized Tax Benefits, Income Tax Penalties and Interest Accrued	0								0
Domestic Tax Authority
Operating Loss Carryforwards [Line Items]
Operating Loss Carryforwards	13,400,000								13,400,000
Foreign Tax Authority
Operating Loss Carryforwards [Line Items]
Operating Loss Carryforwards	$ 25,100,000								25,100,000
Geographic distribution, foreign
Operating Loss Carryforwards [Line Items]
Income before taxes									$ 3,900,000	$ 3,800,000	$ 4,300,000
Minimum | Domestic Tax Authority
Operating Loss Carryforwards [Line Items]
Operating Loss Carryforwards, Expiration Date									Jan. 01, 2028
Minimum | Foreign Tax Authority
Operating Loss Carryforwards [Line Items]
Operating Loss Carryforwards, Expiration Date									Jan. 01, 2034
Maximum | Domestic Tax Authority
Operating Loss Carryforwards [Line Items]
Operating Loss Carryforwards, Expiration Date									Dec. 31, 2034
Maximum | Foreign Tax Authority
Operating Loss Carryforwards [Line Items]
Operating Loss Carryforwards, Expiration Date									Dec. 31, 2035