Organization, Basis of Presentation and Summary of Significant Accounting Policies - Narrative (Details) - USD ($) $ / shares in Units, $ in Millions	1 Months Ended	3 Months Ended			6 Months Ended
	Feb. 28, 2017	Jun. 30, 2017	Mar. 31, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Organization, Basis of Presentation and Summary of Significant Accounting Policies [Line Items]
Period of exemptions under JOBS Act					5 years
Annual gross revenue					$ 1,070.0
Market value of common stock held by non-affiliates					$ 700.0
Number of stock options exercised during the period (in shares)		10,800		1,600	18,800	15,300
Excess tax benefits related to vested and exercised share-based compensation awards			$ 3.3
Increase in basic earnings per share (in USD per share)			$ 0.38
SARs
Organization, Basis of Presentation and Summary of Significant Accounting Policies [Line Items]
Number of stock options exercised during the period (in shares)	1,000,000	212,700		0	1,300,000	0