Available for Sale Investments of Insurance Subsidiary which have Unrealized Losses (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Schedule Of Available For Sale Securities [Line Items]
Fair value, Less than one year	$ 108,012	$ 67,678
Unrealized losses, Less than one year	896	431
Fair value, One year or greater	878	159
Unrealized losses, One year or greater	18	3
Fair value, Total	108,890	67,837
Unrealized losses, Total	914	434
Debt securities
Schedule Of Available For Sale Securities [Line Items]
Fair value, Less than one year	96,133	63,779
Unrealized losses, Less than one year	202	86
Fair value, One year or greater	878
Unrealized losses, One year or greater	18
Fair value, Total	97,011	63,779
Unrealized losses, Total	220	86
Equity by industry
Schedule Of Available For Sale Securities [Line Items]
Fair value, Less than one year	7,031	3,899
Unrealized losses, Less than one year	692	345
Fair value, One year or greater		159
Unrealized losses, One year or greater		3
Fair value, Total	7,031	4,058
Unrealized losses, Total	692	348
Equity by industry | Consumer
Schedule Of Available For Sale Securities [Line Items]
Fair value, Less than one year	381	372
Unrealized losses, Less than one year	36	13
Fair value, Total	381	372
Unrealized losses, Total	36	13
Equity by industry | Healthcare
Schedule Of Available For Sale Securities [Line Items]
Fair value, Less than one year	700	321
Unrealized losses, Less than one year	37	8
Fair value, Total	700	321
Unrealized losses, Total	37	8
Equity by industry | Industrial
Schedule Of Available For Sale Securities [Line Items]
Fair value, Less than one year	1,026	339
Unrealized losses, Less than one year	157	22
Fair value, Total	1,026	339
Unrealized losses, Total	157	22
Equity by industry | Financial Services
Schedule Of Available For Sale Securities [Line Items]
Fair value, Less than one year	860	110
Unrealized losses, Less than one year	81	3
Fair value, One year or greater		159
Unrealized losses, One year or greater		3
Fair value, Total	860	269
Unrealized losses, Total	81	6
Equity by industry | Technology
Schedule Of Available For Sale Securities [Line Items]
Fair value, Less than one year	892	470
Unrealized losses, Less than one year	98	34
Fair value, Total	892	470
Unrealized losses, Total	98	34
Equity by industry | Energy
Schedule Of Available For Sale Securities [Line Items]
Fair value, Less than one year	182	944
Unrealized losses, Less than one year	15	159
Fair value, Total	182	944
Unrealized losses, Total	15	159
Equity by industry | Other
Schedule Of Available For Sale Securities [Line Items]
Fair value, Less than one year	2,990	1,343
Unrealized losses, Less than one year	268	106
Fair value, Total	2,990	1,343
Unrealized losses, Total	268	106
Corporate bonds | Debt securities
Schedule Of Available For Sale Securities [Line Items]
Fair value, Less than one year	42,299	34,859
Unrealized losses, Less than one year	104	60
Fair value, One year or greater	878
Unrealized losses, One year or greater	18
Fair value, Total	43,177	34,859
Unrealized losses, Total	122	60
Debt securities issued by US government agencies | Debt securities
Schedule Of Available For Sale Securities [Line Items]
Fair value, Less than one year	20,503	13,294
Unrealized losses, Less than one year	43	19
Fair value, Total	20,503	13,294
Unrealized losses, Total	43	19
U.S. Treasury notes | Debt securities
Schedule Of Available For Sale Securities [Line Items]
Fair value, Less than one year	33,331	15,626
Unrealized losses, Less than one year	55	7
Fair value, Total	33,331	15,626
Unrealized losses, Total	55	$ 7
Certificates of deposit
Schedule Of Available For Sale Securities [Line Items]
Fair value, Less than one year	4,848
Unrealized losses, Less than one year	2
Fair value, Total	4,848
Unrealized losses, Total	$ 2