Fair Value Measurement (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Assets and liabilities measured at fair value
Total	$ 43,011	$ 45,302
Total investments at fair value	66,625	69,017
Level 1
Assets and liabilities measured at fair value
Total	43,011	45,302
Level 2
Assets and liabilities measured at fair value
Total	0	0
Level 3
Assets and liabilities measured at fair value
Total	0	0
Interest in registered investment companies
Assets and liabilities measured at fair value
Deferred compensation investments valued using net asset value as a practical expedient:	10,016	10,140
Fixed income fund
Assets and liabilities measured at fair value
Deferred compensation investments valued using net asset value as a practical expedient:	13,598	13,575
Deferred compensation investments
Assets and liabilities measured at fair value
Total	28,560	28,558
Deferred compensation investments | Level 1
Assets and liabilities measured at fair value
Total	28,560	28,558
Deferred compensation investments | Level 2
Assets and liabilities measured at fair value
Total	0	0
Deferred compensation investments | Level 3
Assets and liabilities measured at fair value
Total	0	0
Available for sale investment
Assets and liabilities measured at fair value
Total	14,451	16,744
Available for sale investment | Level 1
Assets and liabilities measured at fair value
Total	14,451	16,744
Available for sale investment | Level 2
Assets and liabilities measured at fair value
Total	0	0
Available for sale investment | Level 3
Assets and liabilities measured at fair value
Total	$ 0	$ 0