CONSOLIDATED BALANCE SHEETS (Unaudited) (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Statement Of Financial Position [Abstract]
Accounts receivable, allowance	$ 13,773	$ 13,360
Contract assets, allowance	576	576
Total contract assets, long-term	$ 1,534	$ 1,534
Preferred stock, par value	$ 0.01	$ 0.01
Preferred stock, shares authorized	1,000,000	1,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	349,000,000	349,000,000
Common stock, shares issued	277,696,000	276,705,000
Common stock, shares outstanding	114,792,000	116,114,000
Treasury stock at cost, shares	162,904,000	160,591,000