Comprehensive income (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Apr. 01, 2018	Jan. 01, 2018
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance			$ 4,886,066
Ending balance	$ 4,029,262		4,029,262
Interest rate cap and swap agreements
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	(11,258)	$ (14,502)	(12,408)	$ (12,029)
Cumulative Effect of New Accounting Principle in Period of Adoption					$ 0	$ (2,706)
Unrealized gains (losses)	50	(782)	1,103	(8,967)
Related income tax (expense)	(13)	304	(284)	3,488
Unrealized (losses) gains net	37	(478)	819	(5,479)
Reclassification from accumulated other comprehensive income into net income	2,163	2,070	6,303	6,208
Related income tax (expense)	(557)	(805)	(1,623)	(2,415)
Reclassification from accumulated other comprehensive income into net income net of tax	1,606	1,265	4,680	3,793
Ending balance	(9,615)	(13,715)	(9,615)	(13,715)
Investment securities
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance		4,580	5,662	2,175
Cumulative Effect of New Accounting Principle in Period of Adoption						(5,662)
Unrealized gains (losses)		1,253	0	4,682
Related income tax (expense)		(390)	0	(1,202)
Unrealized (losses) gains net		863	0	3,480
Reclassification from accumulated other comprehensive income into net income		(15)	0	(362)
Related income tax (expense)		6	0	141
Reclassification from accumulated other comprehensive income into net income net of tax		(9)	0	(221)
Ending balance	0	5,434	0	5,434
Foreign currency translation adjustments
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	(10,667)	(17,386)	19,981	(79,789)
Cumulative Effect of New Accounting Principle in Period of Adoption					0	0
Unrealized gains (losses)	(8,827)	29,143	(39,475)	91,546
Related income tax (expense)	0	0	0	0
Unrealized (losses) gains net	(8,827)	29,143	(39,475)	91,546
Reclassification from accumulated other comprehensive income into net income	0	0	0	0
Related income tax (expense)	0	0	0	0
Reclassification from accumulated other comprehensive income into net income net of tax	0	0	0	0
Ending balance	(19,494)	11,757	(19,494)	11,757
Accumulated other comprehensive income (loss)
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	(21,925)	(27,308)	13,235	(89,643)
Cumulative Effect of New Accounting Principle in Period of Adoption					$ 0	$ (8,368)
Unrealized gains (losses)	(8,777)	29,614	(38,372)	87,261
Related income tax (expense)	(13)	(86)	(284)	2,286
Unrealized (losses) gains net	(8,790)	29,528	(38,656)	89,547
Reclassification from accumulated other comprehensive income into net income	2,163	2,055	6,303	5,846
Related income tax (expense)	(557)	(799)	(1,623)	(2,274)
Reclassification from accumulated other comprehensive income into net income net of tax	1,606	1,256	4,680	3,572
Ending balance	$ (29,109)	$ 3,476	$ (29,109)	$ 3,476