Note 12 - Fair Value Measurements - Carrying Amounts and Fair Values (Details) $ in Thousands	Dec. 31, 2019 USD ($)
Interest rate swaps	$ 89,700
Fair Value, Inputs, Level 2 [Member] | Reported Value Measurement [Member]
Interest rate swaps	89,657
Fair Value, Inputs, Level 2 [Member] | Reported Value Measurement [Member] | Senior Credit Facilities [Member]
Long-term debt, including current portion	1,753,045
Fair Value, Inputs, Level 2 [Member] | Estimate of Fair Value Measurement [Member]
Interest rate swaps	89,657
Fair Value, Inputs, Level 2 [Member] | Estimate of Fair Value Measurement [Member] | Senior Credit Facilities [Member]
Long-term debt, including current portion	1,751,241
Money Market Funds [Member] | Fair Value, Inputs, Level 1 [Member] | Reported Value Measurement [Member]
Cash and cash equivalents	46,051
Money Market Funds [Member] | Fair Value, Inputs, Level 1 [Member] | Estimate of Fair Value Measurement [Member]
Cash and cash equivalents	46,051
Commercial Paper [Member] | Fair Value, Inputs, Level 2 [Member] | Reported Value Measurement [Member]
Cash and cash equivalents	54,919
Commercial Paper [Member] | Fair Value, Inputs, Level 2 [Member] | Estimate of Fair Value Measurement [Member]
Cash and cash equivalents	$ 54,824