Fair Value Measurement Financial Assets and Liabilities Accounted for at Fair Value on Recurring Basis (Details) - USD ($)	Jun. 30, 2017	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Transfers between levels 1 and 2	$ 0
Investments under executive deferred compensation plan	23,432,000	$ 22,037,000
Private equity securities	35,000	35,000
Private equity securities measured at net asset value	5,489,000	5,498,000
Foreign currency forward contracts, assets	370,000
Obligations under executive deferred compensation plan	23,432,000	22,037,000
Foreign currency forward contracts, liabilities		182,000
Quoted Prices in Active Markets for Identical Items (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments under executive deferred compensation plan	23,432,000	22,037,000
Private equity securities	35,000	35,000
Private equity securities measured at net asset value	0	0
Foreign currency forward contracts, assets	0
Obligations under executive deferred compensation plan	23,432,000	22,037,000
Foreign currency forward contracts, liabilities		0
Quoted Prices in Active Markets for Similar Items (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments under executive deferred compensation plan	0	0
Private equity securities	0	0
Private equity securities measured at net asset value	0	0
Foreign currency forward contracts, assets	370,000
Obligations under executive deferred compensation plan	0	0
Foreign currency forward contracts, liabilities		182,000
Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Investments under executive deferred compensation plan	0	0
Private equity securities	0	0
Private equity securities measured at net asset value	0	0
Foreign currency forward contracts, assets	0
Obligations under executive deferred compensation plan	$ 0	0
Foreign currency forward contracts, liabilities		$ 0