Stockholders' Equity (Details) - USD ($)		1 Months Ended	3 Months Ended		9 Months Ended
	Aug. 06, 2015	Aug. 31, 2017	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Jun. 30, 2018
Equity [Abstract]
Stock repurchase program, authorized amount	$ 100,000,000
Stock repurchase program, period in force	3 years
Shares repurchased (in shares)		134,900	0	0	0	0
Average sale price (in dollars per share)		$ 58.82
Cost of shares repurchased		$ 7,900,000
Stock repurchase program, remaining authorized repurchase amount							$ 77,700,000