Derivative Instruments - Changes in consolidated statements of comprehensive income related to interest rate derivatives (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Interest rate swaps designated as cash flow hedges:
Unrealized gain (loss) recognized in accumulated other comprehensive income before reclassifications	$ 515	$ 1,249	$ 5,875	$ (17,554)
Amounts reclassified from accumulated other comprehensive income	921	821	2,796	1,154
Income tax (expense) benefit on items recognized in accumulated other comprehensive income	(321)	(451)	(1,918)	3,654
Unrealized gains (losses) on interest rate swaps, net of tax	$ 1,115	$ 1,619	$ 6,753	$ (12,746)