Income Taxes - Pretax Income (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax Examination [Line Items]
Income before income taxes	$ 40,330	$ 102,443	$ 100,024	$ 30,461	$ 54,781	$ 83,743	$ 76,414	$ 34,279	$ 273,258	$ 249,217	$ 148,140
U.S.
Income Tax Examination [Line Items]
Income before income taxes									251,056	217,725	116,852
Outside the U.S.
Income Tax Examination [Line Items]
Income before income taxes									$ 22,202	$ 31,492	$ 31,288