Revenue Recognition (Details) - USD ($)	3 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Increase to opening retained earnings	$ 123,393,000	$ 124,442,000
Contract liabilities	31,500,000	17,600,000
Increase in deferred revenue	6,500,000
Contract assets	0	0
Revenue recognized from deferred revenue	8,700,000
Capitalized contract costs	600,000
Capitalized contract costs amortization	100,000
Capitalized contract cost impairment loss	$ 0
Accounting Standards Update 2014-09
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Increase to opening retained earnings		$ 500,000