Stockholders' Equity (Details Textual) - USD ($)	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Feb. 29, 2020	Feb. 28, 2019	Feb. 14, 2018	Nov. 15, 2017	Oct. 17, 2016
Treasury Stock, Shares, Acquired	218,531	181,642	188,870
Treasury Stock Acquired, Average Cost Per Share	$ 38.66	$ 50.37	$ 50.17
Stock Repurchase Program, Authorized Amount					$ 225,000,000	$ 350,000,000	$ 150,000,000	$ 400,000,000
Stock Repurchased and Retired During Period, Shares	3,987,945	5,849,234	2,081,227
Stock Repurchased and Retired During Period, Value	$ 154,516,000	$ 306,393,000	$ 99,677,000
Stock Repurchase and Retired During Period, Weighted Average Price	$ 38.75	$ 52.38	$ 47.89
Stock Repurchase Program, Remaining Authorized Repurchase Amount	$ 124,700,000
Subsequent Event [Member]
Stock Repurchase Program, Authorized Amount				$ 200,000,000