Derivatives (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Derivative [Line Items]
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, before Tax	$ 2,717,000	$ (39,000)	$ 16,511,000	$ (3,911,000)
Amount reclassified from accumulated other comprehensive loss	(1,148,000)	(2,329,000)	(4,701,000)	(8,054,000)
Cash Flow Hedge Gain (Loss) to be Reclassified within Twelve Months			$ 600,000
Derivative $300M Term [Member]
Derivative [Line Items]
Derivative, Inception Date			Apr. 03, 2017
Derivative, Maturity Date			Dec. 02, 2020
Derivative, Notional Amount	$ 300,000,000		$ 300,000,000
Derivative, Description of Variable Rate Basis			1 Month LIBOR with Floor
Derivative, Fixed Interest Rate	1.824%		1.824%
Interest Rate Cash Flow Hedge Asset at Fair Value	$ (6,410,000)		$ (6,410,000)		$ (1,804,000)
Derivatives 200K @ 1.04770% and 65K @ 1.07000% [Member] [Domain]
Derivative [Line Items]
Derivative, Inception Date			Aug. 01, 2016
Derivative, Maturity Date			Jan. 05, 2022
Derivative, Notional Amount	$ 265,000,000		$ 265,000,000
Derivative, Description of Variable Rate Basis			1 Month LIBOR with Floor
Derivative, Fixed Interest Rate	1.053%		1.053%
Interest Rate Cash Flow Hedge Asset at Fair Value	$ (15,286,000)		$ (15,286,000)		(10,744,000)
Derivative @ 1.30250% 20.0M [Member]
Derivative [Line Items]
Derivative, Inception Date			Apr. 07, 2016
Derivative, Maturity Date			Apr. 01, 2023
Derivative, Notional Amount	$ 20,000,000		$ 20,000,000
Derivative, Description of Variable Rate Basis			1 Month LIBOR
Derivative, Fixed Interest Rate	1.3025%		1.3025%
Interest Rate Cash Flow Hedge Asset at Fair Value	$ (1,310,000)		$ (1,310,000)		(801,000)
Derivative $33M Swap [Member]
Derivative [Line Items]
Derivative, Inception Date			Dec. 01, 2016
Derivative, Maturity Date			Nov. 01, 2023
Derivative, Notional Amount	$ 33,000,000		$ 33,000,000
Derivative, Description of Variable Rate Basis			1 Month LIBOR
Derivative, Fixed Interest Rate	1.49%		1.49%
Interest Rate Cash Flow Hedge Asset at Fair Value	$ (2,151,000)		$ (2,151,000)		(1,166,000)
Derivative @ 2.36600% 37.5K [Member] [Domain]
Derivative [Line Items]
Derivative, Inception Date			Jun. 02, 2017
Derivative, Maturity Date			Jun. 02, 2027
Derivative, Notional Amount	$ 37,500,000		$ 37,500,000
Derivative, Description of Variable Rate Basis			1 Month LIBOR with Floor
Derivative, Fixed Interest Rate	2.366%		2.366%
Interest Rate Cash Flow Hedge Asset at Fair Value	$ (1,645,000)		$ (1,645,000)
Interest Rate Cash Flow Hedge Liability at Fair Value					177,000
Swap [Member]
Derivative [Line Items]
Cash Flow Hedge Gain (Loss) to be Reclassified within Twelve Months			7,900,000
Fair Value, Measurements, Recurring [Member]
Derivative [Line Items]
Interest Rate Cash Flow Hedge Asset at Fair Value	(26,802,000)		(26,802,000)		(14,515,000)
Interest Rate Cash Flow Hedge Liability at Fair Value					177,000
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member]
Derivative [Line Items]
Interest Rate Cash Flow Hedge Asset at Fair Value	(26,802,000)		(26,802,000)		(14,515,000)
Interest Rate Cash Flow Hedge Liability at Fair Value					177,000
Interest Rate Cash Flow Hedge Derivative at Fair Value, Net	26,802,000		26,802,000		$ 14,338,000
Parent Company [Member]
Derivative [Line Items]
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, before Tax	2,717,000	(39,000)	16,511,000	(3,911,000)
Interest Expense	$ 36,618,000	$ 34,679,000	$ 111,477,000	$ 97,285,000