Derivatives and Hedging (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2015
Interest Rate Derivatives
Notional value	$ 1,790,751,000		$ 1,790,751,000		$ 1,792,251,000
Unrealized gains (losses) included in accumulated other comprehensive loss	(42,200,000)		(42,200,000)		(16,600,000)
Amount of ineffectiveness on hedges	0	$ 0	0	$ 0
Net unrealized losses in accumulated other comprehensive loss expected to be reclassified into interest expense within the next 12 months	15,700,000		15,700,000
Interest Rate Cash Flow Hedge Derivative at Fair Value, Net	42,216,000		42,216,000		16,602,000
Designated as Hedging Instrument | Swap-cash flow, hedge type one
Derivatives and Hedging
Interest rate swap liability	(2,459,000)		(2,459,000)		(1,014,000)
Interest Rate Derivatives
Notional value	$ 275,000,000		$ 275,000,000		275,000,000
Interest rate	1.1175%		1.1175%
Designated as Hedging Instrument | Swap-cash flow, hedge type two
Derivatives and Hedging
Interest rate swap liability	$ (3,189,000)		$ (3,189,000)		(2,190,000)
Interest Rate Derivatives
Notional value	$ 175,000,000		$ 175,000,000		175,000,000
Interest rate	1.5625%		1.5625%
Designated as Hedging Instrument | Swap-cash flow, hedge type three
Derivatives and Hedging
Interest rate swap liability	$ (3,415,000)		$ (3,415,000)		(2,478,000)
Interest Rate Derivatives
Notional value	$ 175,000,000		$ 175,000,000		175,000,000
Interest rate	1.635%		1.635%
Designated as Hedging Instrument | Swap-cash flow, hedge type four
Derivatives and Hedging
Interest rate swap liability	$ (460,000)		$ (460,000)		(312,000)
Interest Rate Derivatives
Notional value	$ 16,253,000		$ 16,253,000		16,418,000
Interest rate	1.825%		1.825%
Designated as Hedging Instrument | Swap-cash flow, hedge type five
Derivatives and Hedging
Interest rate swap liability	$ (433,000)		$ (433,000)		(279,000)
Interest Rate Derivatives
Notional value	$ 16,253,000		$ 16,253,000		16,418,000
Interest rate	1.751%		1.751%
Designated as Hedging Instrument | Swap-cash flow, hedge type six
Derivatives and Hedging
Interest rate swap liability	$ (1,129,000)		$ (1,129,000)		(765,000)
Interest Rate Derivatives
Notional value	$ 39,893,000		$ 39,893,000		40,298,000
Interest rate	1.825%		1.825%
Designated as Hedging Instrument | Swap-cash flow, hedge type seven
Derivatives and Hedging
Interest rate swap liability	$ (1,088,000)		$ (1,088,000)		(701,000)
Interest Rate Derivatives
Notional value	$ 40,877,000		$ 40,877,000		41,292,000
Interest rate	1.751%		1.751%
Designated as Hedging Instrument | Swap-cash flow, hedge type eight
Derivatives and Hedging
Interest rate swap liability	$ (502,000)		$ (502,000)		(340,000)
Interest Rate Derivatives
Notional value	$ 17,730,000		$ 17,730,000		17,910,000
Interest rate	1.825%		1.825%
Designated as Hedging Instrument | Swap-cash flow, hedge type nine
Derivatives and Hedging
Interest rate swap liability	$ (446,000)		$ (446,000)		(287,000)
Interest Rate Derivatives
Notional value	$ 16,745,000		$ 16,745,000		16,915,000
Interest rate	1.751%		1.751%
Designated as Hedging Instrument | Swap-cash flow, hedge type ten
Derivatives and Hedging
Interest rate swap liability	$ (4,860,000)		$ (4,860,000)		(3,186,000)
Interest Rate Derivatives
Notional value	$ 125,000,000		$ 125,000,000		125,000,000
Interest rate	2.018%		2.018%
Designated as Hedging Instrument | Swap-cash flow, hedge type eleven
Derivatives and Hedging
Interest rate swap liability	$ (3,682,000)		$ (3,682,000)		(2,308,000)
Interest Rate Derivatives
Notional value	$ 100,000,000		$ 100,000,000		100,000,000
Interest rate	1.944%		1.944%
Designated as Hedging Instrument | Swap-cash flow, hedge type twelve
Derivatives and Hedging
Interest rate swap liability	$ (2,281,000)		$ (2,281,000)		(115,000)
Interest Rate Derivatives
Notional value	$ 125,000,000		$ 125,000,000		125,000,000
Interest rate	1.2715%		1.2715%
Designated as Hedging Instrument | Swap-cash flow, hedge type thirteen
Derivatives and Hedging
Interest rate swap liability	$ (1,622,000)		$ (1,622,000)		(321,000)
Interest Rate Derivatives
Notional value	$ 100,000,000		$ 100,000,000		100,000,000
Interest rate	1.9615%		1.9615%
Designated as Hedging Instrument | Swap-cash flow, hedge type fourteen
Derivatives and Hedging
Interest rate swap liability	$ (737,000)		$ (737,000)		(87,000)
Interest Rate Derivatives
Notional value	$ 50,000,000		$ 50,000,000		50,000,000
Interest rate	1.85%		1.85%
Designated as Hedging Instrument | Swap-cash flow, hedge type fifteen
Derivatives and Hedging
Interest rate swap liability	$ (711,000)		$ (711,000)		(62,000)
Interest Rate Derivatives
Notional value	$ 50,000,000		$ 50,000,000		50,000,000
Interest rate	1.8115%		1.8115%
Designated as Hedging Instrument | Swap-cash flow, hedge type sixteen
Derivatives and Hedging
Interest rate swap liability	$ (333,000)		$ (333,000)		(9,000)
Interest Rate Derivatives
Notional value	$ 25,000,000		$ 25,000,000		25,000,000
Interest rate	1.7445%		1.7445%
Designated as Hedging Instrument | Swap-cash flow, hedge type seventeen
Derivatives and Hedging
Interest rate swap asset					98,000
Interest rate swap liability	$ (504,000)		$ (504,000)
Interest Rate Derivatives
Notional value	$ 33,000,000		$ 33,000,000		33,000,000
Interest rate	1.80%		1.80%
Designated as Hedging Instrument | Swap-cash flow, hedge type eighteen
Derivatives and Hedging
Interest rate swap asset					245,000
Interest rate swap liability	$ (1,253,000)		$ (1,253,000)
Interest Rate Derivatives
Notional value	$ 82,000,000		$ 82,000,000		82,000,000
Interest rate	1.80%		1.80%
Designated as Hedging Instrument | Swap-cash flow, hedge type nineteen
Derivatives and Hedging
Interest rate swap asset					104,000
Interest rate swap liability	$ (535,000)		$ (535,000)
Interest Rate Derivatives
Notional value	$ 35,000,000		$ 35,000,000		35,000,000
Interest rate	1.80%		1.80%
Designated as Hedging Instrument | Swap-cash flow, hedge type twenty
Derivatives and Hedging
Interest rate swap liability	$ (6,558,000)		$ (6,558,000)		(2,196,000)
Interest Rate Derivatives
Notional value	$ 143,000,000		$ 143,000,000		143,000,000
Interest rate	1.80816%		1.80816%
Designated as Hedging Instrument | Swap-cash flow, hedge type twenty one
Derivatives and Hedging
Interest rate swap liability	$ (1,971,000)		$ (1,971,000)		(97,000)
Interest Rate Derivatives
Notional value	$ 50,000,000		$ 50,000,000		50,000,000
Interest rate	1.6125%		1.6125%
Designated as Hedging Instrument | Swap-cash flow, hedge type twenty two
Derivatives and Hedging
Interest rate swap asset					59,000
Interest rate swap liability	$ (1,828,000)		$ (1,828,000)
Interest Rate Derivatives
Notional value	$ 50,000,000		$ 50,000,000		50,000,000
Interest rate	1.5555%		1.5555%
Designated as Hedging Instrument | Swap-cash flow, hedge type twenty three
Derivatives and Hedging
Interest rate swap liability	$ (2,220,000)		$ (2,220,000)		(361,000)
Interest Rate Derivatives
Notional value	$ 50,000,000		$ 50,000,000		50,000,000
Interest rate	1.7095%		1.7095%
Interest Expense
Interest Rate Derivatives
Amount reclassified from accumulated other comprehensive income into interest expense	$ 4,100,000	$ 4,200,000	$ 8,300,000	$ 8,300,000
Accounts payable and other liabilities | Interest rate swap
Derivatives and Hedging
Interest rate swap liability	$ (42,200,000)		$ (42,200,000)		(17,100,000)
Prepaid expenses and other assets | Interest rate swap
Derivatives and Hedging
Interest rate swap asset					$ 500,000