Company Information and Significant Accounting Policies - Income Statement (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Feb. 01, 2018
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenues	$ 209,394	$ 188,868
Operating expenses	163,145	143,465
Income before income taxes	30,461	34,279
Income taxes	5,375	10,010
Net income	$ 25,086	$ 24,269
Diluted earnings per share (in dollars per share)		$ 0.43
As Previously Reported
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenues		$ 197,898
Operating expenses		145,391
Income before income taxes		41,383
Income taxes		12,639
Net income		$ 28,744
Diluted earnings per share (in dollars per share)		$ 0.51
Accounting Standards Update 2014-09 | Adoption of Topic 606
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Revenues		$ (9,030)
Operating expenses		(1,926)
Income before income taxes		(7,104)
Income taxes		(2,629)
Net income		$ (4,475)
Diluted earnings per share (in dollars per share)		$ (0.08)
WoodSpring
Revenue, Initial Application Period Cumulative Effect Transition [Line Items]
Business acquisition, percentage of voting interests acquired			100.00%